I later learned that the green scum that plagued the lake during summer months was a sign that the lake was actually overly alive. It gained its morbid reputation because when blooms of the tiny plant-like organisms die-off, the decomposition process consumes oxygen. In extreme cases, it creates an unpleasant, smelly mess and literally sucks the oxygen from the water.

With anoxic conditions like these, walleye pike and yellow perch alike turn belly-up and die or gasp for breath at the surface, unable to syphon oxygen from the water that flows through their gills.

This is what the surface of Lake Erie looked like west of the Erie Islands in 2004. Photo by Lisa Borre.

Algae gets a bad rap sometimes, a reputation not always deserved. Many varieties of algae are beneficial to lakes, providing the basis of the food chain that supports the entire ecosystem. Other types, like cyanobacteria, produce toxins that are harmful to humans and can even cause death to animals that consume it. Large blooms, even non-toxic ones, affect ecosystem health.

Too much phosphorus, an essential element for plant growth, is the usual culprit in triggering algal blooms in lakes. It washes into lakes from agricultural runoff, sewage treatment plants, lawn fertilizer, water treatment plants, and septic systems. At the right water temperature, the more phosphorus there is in the water, the more algal growth you get.

Lake Erie suffered from toxic algae blooms in the 1970s, but with a major effort to reduce phosphorus loading, the blooms disappeared for nearly two decades. By the mid 1990s, conditions began to deteriorate again. When I sailed across the lake in late summer 2004, an algae bloom stretched from the Erie Islands to the western shore.

Agricultural and Meteorological Trends Cause Massive 2011 Bloom

A recent forensic-like study of the 2011 bloom, published in the Proceedings of the National Academy of Sciences, gives new insight about possible causes of these extreme events.

The National Science Foundation awarded a five-year grant to a team of researchers to study the effects of climate-change induced extreme events on water quality and ecology in the Great Lakes system. “It was a coincidence that the project began in January 2011, and this perfect case study popped up out of nowhere,” a researcher at the Carnegie Institution for Science and principal investigator for the study, Anna M. Michalak explained to me.

Using a holistic approach, the team brought together high-tech tools and sophisticated statistical analysis to assess whether the record-setting algal bloom in Lake Erie was driven by an unfortunate combination of circumstances or is a sign of things to come. They concluded that trends in agricultural practices, increased intensity of precipitation, weak lake circulation, and quiescent conditions conspired to yield the massive bloom.

The main cause of the massive bloom was the confluence of long-term trends in nutrient management practices on farms and a changing climate, including more frequent extreme precipitation events. They study says these “are consistent with expected future conditions.” This means that unless something is done to reduce the input of nutrients from agriculture and other obvious sources or to stop changes in climate already underway, nuisance algal blooms are likely to become more common in the future.

Satellite photo of the Great Lakes showing the 2011 toxic algae bloom (light green) reaching into the central basin of Lake Erie. Source: NASA.

Michalak recommends that future management plans be guided by science like hers and her colleagues’ to mitigate impacts, but she doesn’t want her team’s findings to be misunderstood as placing the blame on farmers. “Farmers and land managers deserve due credit for implementing a variety of recommended conservation practices,” she told me, “and these have gone a long way to limiting soil erosion and reducing carbon loss.”

In 2011, severe spring rain events made it difficult for farmers to apply fertilizers without having the nutrients washed away immediately. Fertilizers are expensive. “It’s no more in a farmer’s interest to have fertilizers end up in the lake than it is for the environment,” said Michalak. She cited improved forecasting of spring storms to better guide the timing of fertilizer applications as one example where science and management could come together to address the problem.

As certain agricultural practices have increased in the region over the past ten years, so has the loading of “dissolved reactive phosphorus” (DRP), a form of “bioavailable” phosphorus that is readily available for uptake by plants, including nuisance algae. Although the total inputs of phosphorus have decreased since the 1970s, the loading of DRP from nonpoint sources has increased in recent years. Michalak says that reducing these loads will be key to restoring the lake again.

Total phosphorus loading to Lake Erie has been reduced since the 1970s, but nonpoint sources have not. Image courtesy of the IJC.

Although not considered a major factor in the 2011 bloom, converting land to corn production for the biofuel industry has more recently become a trend in the Lake Erie watershed. This fertilizer-intensive crop could further exacerbate the problem of harmful algae blooms, Michalak told me.

Another more subtle change underway is the rising water temperatures in all of the Great Lakes. “As Lake Erie warms, it increases the likelihood that the water will be warm enough earlier in the season when most of the nutrients are delivered to the lake,” said Michalak. “It’s a timing game. If the nutrients are still available when the lake warms up, it could trigger an algae bloom.”

A satellite image of Lake Erie on Sept. 3, 2011, overlaid on a map of the lake and its tributaries. This image shows the bloom about six weeks after its initiation in the lake’s western basin. Map courtesy of Michigan Sea Grant.

What is Being Done to Restore the Lake?

The International Joint Commission (IJC) is one of many agencies focused on the algae problems in Lake Erie once again. Under the Great Lakes Water Quality Agreement (GLWQA), first signed in 1972 and most recently updated in 2012, the IJC advises the U.S. and Canadian governments on how to protect the lakes.

Declining water quality in Lake Erie is one of four priorities for the IJC’s work for the next three years. The IJC’s Lake Erie Ecosystem Priority, or LEEP, is aptly named. “We’d like the lake to improve by leaps and bounds,” the project website states.

According to the updated GLWQA, the governments have five years to put plans into place for reducing phosphorus inputs to Lake Erie. But after seeing the major bloom two years ago, the IJC set a more ambitious goal for achieving measurable reductions by 2015, explained Raj Bejankiwar, a physical scientist and phosphorus expert at the IJC. They have commissioned a series of studies and convened experts to develop findings and recommendations. A draft report is due out by the end of May and public consultations are planned this summer.

The IJC plans to make the case for more urgent action on Lake Erie during Great Lakes Week in September. The Great Lakes Restoration Conference will be held in Milwaukee the same week.

“The LEEP project is not just pure science. We’re also looking at socio-economics and stakeholder concerns. We can only solve this problem by looking at the issue in a broader context,” said Bejankiwar.

The project will enhance efforts underway as part of the larger Great Lakes Restoration Initiative (GLRI) on the U.S. side and a pledged $16 million investment in nutrient management on the Canadian side.

“Now scientists are telling us to be prepared for further challenges linked to climate change,” Bejankiwar told me. Warmer water, less ice cover, more intense rain events, and changing land use patterns are just some of the variables that might complicate future restoration efforts. “For these reasons, the IJC is promoting an adaptive approach to management of the Great Lakes,” he says.

Maumee River at Mary Jane Thurston State Park in Grand Rapids, Ohio. Photo by Dustin M. Ramsey.

The Nature Conservancy (TNC), one of many groups working to protect the Great Lakes, is actively acquiring, restoring, and managing land throughout the Lake Erie basin. “TNC is trying to find practical solutions by working with farmers to implement agricultural best management practices while keeping an eye on the impacts of climate change,” said Patrick Doran, Director of Conservation for Michigan at The Nature Conservancy.

Lake Erie’s largest tributary, the Maumee River, is one of three GLRI priority areas for reducing harmful algae in the Great Lakes watershed. It empties into the shallow, western basin of the lake, the area most affected by harmful algae blooms. Much of TNC’s work in this area is focused in the Maumee and Grand River watersheds.

Toxic Algae Blooms Becoming a Global Concern

Unfortunately, the problem of harmful algal blooms is not unique to Lake Erie. As lakes become warmer and extreme precipitation events become more common with climate change, more lakes throughout the world are experiencing cyanobacteria blooms.

Lake Winnipeg in Canada was declared the most endangered lake in the world last year because of toxic algae blooms. Lake Zurich in Switzerland and Lake Taihu in China are among other notorious examples. Visit this National Geographic photo gallery to see more examples.

Those concerned with the health of lakes are searching for solutions to this nagging problem around the globe. This will be a topic of a future post, so stay tuned.

Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, Maryland. With her husband, she co-founded LakeNet, a world lakes network, and co-wrote a sailing guide called “The Black Sea” based on their voyage around the sea in 2010. A native of the Great Lakes region, she served as coordinator of the Lake Champlain Basin Program in the 1990s. She is now an active member of the Global Lake Ecological Observatory Network. 

A penny provides scale for the size of micro plastics being found in the Great Lakes ‘Garbage Patch.’ Credit: 5Gyres.

Until recently, my concept of a ‘garbage patch’ was of an area of ocean with large pieces of floating debris, the kind of stray fishing gear and trash from ships and shorelines that collect where currents form eddies far from view of most people.

Having seen my share of sea trash in 20,000+ miles of lake and ocean sailing and even untangled sheets of plastic and thick ropes from the propeller and rudder of my 37-foot sailboat, I was shocked to learn that the kind of garbage scientists are most concerned about is invisible to the naked eye. They’re finding tiny bits of plastic known as “micro-plastics” floating near the surface of the water in high concentrations. The particles are so small that a microscope is needed to even see them.

The scary news this week was about a garbage patch discovered in the Great Lakes last year. Although scientists have studied plastic pollution in the oceans since NOAA researchers discovered the “Great Pacific Garbage Patch” in 1988, a team of scientists is conducting the first-of-its-kind research on the open water of the Great Lakes. One of the team members presented preliminary results of a study on the topic at meeting of the American Chemical Society.

The team of researchers studying the Great Lakes ‘Garbage Patch’ in 2012. Credit: 5Gyres.

I spoke with Lorena Rios-Mendoza, an environmental chemist at the University of Wisconsin-Superior, and found that the buzz was certainly justified. Her background includes studying plastic debris and persistent organic pollutants (POPs) in the Pacific Garbage Patch and in the Southern Ocean. Now an assistant professor at the University of Wisconsin-Superior, she has turned her attention to these same issues on the North American Great Lakes.

“I’m interested in learning more about what happens to persistent organic pollutants when they attach to the plastic particles,” Rios-Mendoza told me. She is now studying 110 fish samples to see if they have plastic debris in their guts and to learn more about what happens to POPs associated with the plastic pollution. She wonders whether the accidental consumption of tiny bits of plastic by fish might be a new source for toxins in the food chain.

Sam Mason (on right) collecting samples of plastic pollution aboard the “Niagara” on the Great Lakes. Credit: 5Gyres.

Rios-Mendoza is working with a team of researchers led by Sherri “Sam” Mason, a SUNY-Fredonia chemistry professor and researcher at the forefront of research on plastic pollution within freshwater ecosystems, including the Great Lakes. Mason is actually an atmospheric chemist, but she also has a passion for environmental sustainability. A few years ago, a colleague at Niagara University invited her to teach an environmental science course aboard the Flagship Niagara, a rebuilt version of a tall ship used during the War of 1812 that is now used for on-water education programs. Having lived near the shores of Lake Erie for over ten years, she had never been out on the lake, let alone a sailboat, before teaching the summer course. Mason’s time on the water inspired her to take up an entirely new area of research: studying plastic pollution in the Great Lakes.

Modeling herself after scientists like Rachel Carson who are committed to sharing relevant research, Mason found that studying and trying to raise awareness about plastic pollution in freshwater systems suited her. “This is a fantastic area for research because the information is much needed and relevant to the scientific community and to people concerned about the Great Lakes,” she told me.

Mason and Rios-Mendoza have been working in collaboration with the 5Gyres Institute, a research and education group studying garbage patches in five subtropical gyres in the Atlantic, Pacific, and Southern Oceans.

Tiny pieces of plastic pollution found while sampling in Lake Erie. Credit: 5Gyres.

The team of researchers studying the Great Lakes wasn’t surprised to find plastic pollution, especially in Lake Erie, the smallest (by volume) and shallowest of the five lakes. They did find something interesting when comparing their results to the research in oceans. The concentration of PAHs (polyaromatic hydrocarbons) in Lake Erie is twice as high as what is found in the world oceans. “This makes sense because the oceans are so much larger – there’s a dilution factor,” Rios-Mendoza said.

Something else the research team didn’t expect was the predominance of micro-plastic particles (less than 1 millimeter in diameter). In the world’s oceans, scientists have found higher percentages of debris in the 1-5 millimeter diameter size range as compared to the micro-plastics. Mason suspects that this is because of the larger ratio of shoreline to open water, creating an abrasive action to break down the plastic.

A sample taken from Lake Erie showing micro plastics less than 1 millimeter in size. Credit: 5Gyres.

They’re finding tiny, perfectly round beads of plastic in many of the samples, and this might hold another clue about the source of particles. “The cosmetics industry uses plastic micro-beads in soaps, toothpaste and other products. Because the products are not designed for ingestion, they don’t have to test for this. It’s completely unregulated and may be a significant source of micro-plastics finding their way into the environment,” she says.

Finding the sources of plastic pollution and getting a better idea of the degradation process is the subject of follow-up studies Mason and her team are working on.

More research is needed to compare the amount of plastic pollution from one lake to the next, but Rios-Mendoza explained to me that it takes more than two hours of towing the fine-mesh sampling net in Lake Superior to recover the amount of plastic in a 30-minute trawl from Lake Erie. The team plans to sample the St. Lawrence River and Lakes Erie, Michigan, and Ontario this summer, and as funding allows, to carry out more systematic studies of all five lakes.

How do plastics end up in oceans and now lakes? Well to begin with, we have become a throwaway society. We’re using and throwing away more and more plastics, sometimes after only using them once. The plastics are designed to last a long time, more than 500 years in some cases, Mason told me. In the U.S. alone, we consume “billions” of plastic bags and bottles. According to the 5Gyres website, only five percent of the plastics produced for things like water bottles, cups, utensils, toys and gadgets are recycled. “Roughly 50% is buried in landfills, some is remade into durable goods, and much of it remains unaccounted for, lost in the environment where it ultimately washes out to sea,” their website states.

From the deck of a boat on Lake Erie, micro plastics are not visible in the water. Photo by Lisa Borre.

Plastic pollution is not only a problem in the water but along beaches and shorelines as well. Beaches in Hawaii were found to contain 50% sand and micro-plastics, Rios-Mendoza told me. The research team has not studied the amount of micro-plastics on Great Lakes beaches yet.

The Alliance for the Great Lakes leads an Adopt-a-Beach program to address the problem of beach pollution throughout the Great Lakes region. Mason participates in the Adopt-a-Beach program and says that her students are always surprised by how much trash they find on a beach that doesn’t look that bad at the outset. She is also leading a one-week course this summer in collaboration with Pangaea Expeditions, collecting samples for future research along the way.

“People need to be aware that we are the source of the problem, and because of this, we need to be part of the solution,” Mason said. “We all need to become aware of how much plastic we use in our lives and avoid using single-use products. Don’t buy water in plastic bottles or cosmetic products with micro beads. Bring re-usable bags to the store with you. Simple things like this make a big difference, but it’s also important to keep talking about this issue and raising awareness about how it affects the Great Lakes and the world’s oceans.”

It turns out that even this observant sailor has sailed right through garbage patches on the Atlantic Ocean and Great Lakes without noticing anything but the deep blue water that appears infinitely transparent. Now I realize what all the fuss is about. These new findings give me all the more reason to find ways to reduce, re-use, and recycle plastic at home and on my boat.

In short, I need to do my part to reduce plastic pollution in the world’s lakes and oceans.

Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, Maryland. With her husband, she co-founded LakeNet, a world lakes network, and co-wrote a sailing guide called “The Black Sea” based on their voyage around the sea in 2010. She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program in the 1990s.

A fishing village on Lake Tanganyika. Photo by Catherine O’Reilly.

Tropical lakes in East Africa don’t grab headlines the way polar bears do, but climate change is having an effect on them, too. Although the changes are not as visible as melting polar ice caps, they are no less real.

As in many lakes around the world, water temperature is on the rise in Lake Tanganyika. This and other climate-related factors are causing subtle but significant changes that threaten the ecological stability of the lake and the livelihoods of people who depend on it.

With air temperatures across tropical Africa expected to rise as much as 2–5 degrees Celsius (3.5–9 degrees Fahrenheit) over the next 50-100 years, warming lake trends are also expected to continue. The changes underway serve as early warning signs, not just for the lake region, but perhaps, for the planet as a whole.

Considered one of the African Great Lakes, Tanganyika is the world’s second largest lake (by volume) and second deepest, after Russia’s Lake Baikal. It contains 17 percent of the world’s surface freshwater – almost as much water as all five of the North American Great Lakes combined. At more than 10 million years old, Tanganyika is among an elite group of only 20 or so ancient lakes in the world.

Lake Tanganyika as seen from space. Source: NASA.

Lake Tanganyika also ranks in the top tier of some 250 lakes found to have globally significant freshwater biodiversity.

Four countries border the lake: Burundi, Democratic Republic of Congo (DR Congo), Tanzania, and Zambia. This poses a major challenge for lake conservation and management efforts.

About 10 million people live in the lake’s drainage basin, and the population is growing rapidly (by a rate of 2.5 percent per year), according to a 2006 Brief about the lake. In the nearshore areas of the lake, the rate of growth is nearly double the national average at 4 percent per year.

The population growth in nearshore areas around Lake Tanganyika is nearly double the national average. Photo by Catherine O’Reilly.

For the most part, the lake has relatively high quality water, except in a few areas where urban and industrial runoff has affected the lake. This is in part due to the lake’s enormous volume, which acts as a buffer to problems that plague some of the other African Great Lakes, such as overfishing and invasive weed growth on Lake Victoria.

Over-exploitation of the fishery and siltation caused by erosion from deforested areas are considered the main threats to the health of the lake. With increased population pressure, the ongoing problem of siltation, and now climate change added to the mix, fish stocks, biodiversity, and water quality are expected to decline.

Given the importance of Lake Tanganyika, I wondered why we haven’t heard more about the effects on lakes such as this in the climate change dialogue. To learn more, I spoke with two scientists who conduct research on the lake.

Lake Tanganyika still has relatively high water quality. Photo by Catherine O’Reilly.

The Effects of Climate Change

Catherine M. O’Reilly, an assistant professor of geology at Illinois State University, talked with me last fall at a meeting of the Global Lake Ecological Observatory Network (GLEON).

O’Reilly began studying the lake as part of a team looking at the impacts of deforestation in the Tanganyika watershed, where an astounding 100 percent of the native vegetation has been cleared in the northern portion of the watershed. It might not seem obvious, but if you’re interested in learning more about historical land use changes in the lake’s watershed or about the biological communities that have lived in the lake, a good place to look is in the mud at the bottom of the lake.

Siltation caused by erosion from deforestation is another main threat to Lake Tanganyika. Photo by Catherine O’Reilly.

The particles in the lake and those washing into it, through rivers, streams, shoreline erosion, and even pollution discharges, eventually settle out to the bottom along with the decomposed remains of aquatic organisms. In a lake as deep as Tanganyika, these particles are essentially locked away in layers of mud. The bottom sediments are like a secure vault, storing the ecological history of the lake and its surrounding watershed. In the case of Lake Tanganyika, this process has been occurring for millions of years, making it a treasure trove of information for scientists to study trends, such as the effects of climate change.

By examining sediment cores taken from the lake’s depths, O’Reilly noticed a chemical signal (the carbon isotope signal) that didn’t seem to make sense. Upon further examination, she discovered that this signal suggested that the lake responded to climate warming. Interestingly enough, the 2003 results of her team’s research were published in Nature simultaneously with another team’s results (Verburg et al.) in Science. They had independently reached the same conclusions using slightly different methods.

Researchers can unlock the history of the lake by studying sediment cores. Photo by Catherine O’Reilly.

Lake Tanganyika is Warming

O’Reilly found that water temperatures in Lake Tanganyika have warmed 0.1 degrees Celsius (0.18 degrees Fahrenheit) per decade or 1 degree Celsius (1.8 degrees Fahrenheit) over for the past 100 years. Not only is this affecting the ecological stability of the lake, it has resulted in a 20 percent reduction in biological productivity in the lake.

Scientists are concerned about how continued warming will affect fish stocks and the lake’s rich biodiversity. Reduced fish catches would impact millions of people living in the lake region, many whom live on less than a dollar a day and depend on the lake for basic human needs – the protein from fish and clean water to drink.

More recent global assessments show that the rate of warming in Lake Tanganyika is consistent with other lakes around the world. Although it is not warming as rapidly as some lakes in the northern hemisphere, O’Reilly told me that even small changes in lake temperature can cause major disruptions in the lake’s ecological stability.

These larger predator fish feed on the sardines (locally called ‘dagaa’) in the lake. A lake temperature change of less than 2 degrees Fahrenheit in the last 100 years has resulted in a 20 percent reduction in biological productivity in the lake.
Photo by Catherine O’Reilly.

An Ancient Lake with Globally Significant Biodiversity

Peter McIntyre, an aquatic ecology professor at the University of Wisconsin-Madison’s Center for Limnology, spoke with me about why scientists are so concerned about the changing dynamics in Lake Tanganyika. His research focuses on conserving both biodiversity and ecosystem dynamics, and he specializes in freshwater fish.

The lake was formed slowly over millions of years as the East African plate separated from the main African plate, creating a massive rift valley that continues to expand today (though very slowly), McIntyre explained. The lake now sits at the headwaters of the mighty Congo River, which carries the water from the west side of Lake Tanganyika on a journey nearly 3,000 miles (4,700 km) across the African continent to the Atlantic Ocean.

“The emergence of a massive lake in the Upper Congo basin provided a perfect opportunity for all kinds of river animals to diversify into hundreds and hundreds of species endemic to the lake,” says McIntyre. Large numbers of fish, snails, and tiny crustaceans (known as ostracods) flourished. Smaller evolutionary radiations of crabs, shrimp, and leaches also occurred, resulting in a lake with some of the greatest freshwater biological diversity on the planet. There is even an endemic sub-species of aquatic cobra, McIntyre told me.

The clear water of Lake Tanganyika supports some of the greatest freshwater biodiversity on the planet.
Photo by Catherine O’Reilly.

Surface Water Warming More Rapidly Than Its Depths

The lake is remarkable in other ways, not the least of which is its extreme depth. At almost a mile deep (1.472 km), it is among a special class of lakes that remains permanently stratified. The warmer surface waters never mix completely with the cooler water at depth. Although partial mixing events occur from time to time, these are relatively short-lived.

“Because of the temperature differences, the bottom water is effectively isolated from the surface water,” said McIntyre. He describes the temperature boundary in the lake, typically at a depth of 60 or 70 meters, as acting like a drain for nutrients and energy from the surface. When these materials reach the oxygen-starved bottom of the lake, the difference in temperature between the upper and lower layers acts as a barrier – like oil on water – that inhibits the mixing that could replenish nutrients in brightly-lit surface waters.

The lake’s surface waters never mix completely with the deeper water. Photo by Catherine O’Reilly.

Lake Tanganyika happens to have one of the longest temperature records of any lake in the world. A century ago, scientists began measuring temperature profiles to a depth of 1,000 meters using insolated bottles and specialized thermometers. Temperature studies were also conducted in the 1920s, 1940s, 1970s, and then more frequently in the 2000s. Although a sparse record, O’Reilly says that it paints a clear picture.

Nowadays, the technology has greatly advanced. Researchers use fancy instruments to precisely measure the temperature change from the surface all the way to the bottom of the lake. For the past four years, McIntyre and his colleagues have continued to collect temperature profiles of the lake.

From these records, scientists are finding that Lake Tanganyika’s surface waters are warming more rapidly than its depths. This has the effect of creating an even sharper gradient between the upper and lower layers of the lake, and thus creating an even greater barrier to wind-induced mixing.

Lake Tanganyika’s surface waters are warming more rapidly than its depths. Photo by Catherine O’Reilly.

Small Changes in Temperature Can Have Big Impacts on Tropical Lakes

From the standpoint of lake physics, it turns out that warm, tropical lakes are more sensitive to changes in temperature than lakes in cooler climates. O’Reilly explained that the warmer the water is, the more energy is required to mix it. In a typical northern lake that cools in the fall and winter, the energy from wind is enough to mix the lake. “The amount of energy required to maintain mixing, which is very important for circulating nutrients, is huge in Lake Tanganyika,” she says.

Finding the ideal nutrient concentrations in a lake is a delicate balancing act. With too little, the lake cannot support aquatic life. With too much, the lake becomes overly productive and could develop harmful algae blooms and excessive weed growth. Another unique feature about Lake Tanganyika is that its surface waters are low in nutrients yet support an incredibly productive fishery. This is possible because of an occasional upwelling of nutrient rich water from the bottom of the lake.

McIntyre describes the upwelling as being like a small burp of deep water into the surface. “The burps provide a critical annual injection of nutrients to the nearshore area where most of the lake’s species are found,” he said, “and these species are very good at storing the nutrients until the next upwelling occurs.” He says that researchers are already seeing signs that the amount of mixing has decreased. And help is unlikely to come from the winds; O’Reilly has gathered evidence of decreasing winds in the region.

The greatest biodiversity in Lake Tanganyika is found in the nearshore area. Photo by Catherine O’Reilly.

Is the Lake Approaching a Tipping Point?

McIntyre worries that a reduction in the magnitude and frequency of upwelling events caused by climate-related changes could undercut the stability of the entire ecosystem. “The lake’s incredible biodiversity depends on the high productivity fueled by the annual upwelling of nutrients,” he says. If that aspect of the lake’s annual cycle is lost, the whole system could cross a ‘tipping point’ where the changes become permanent.

O’Reilly expressed grave concerns, too. When analyzing the data, she noticed that the lake has not recovered as well as it used to from more extreme conditions, such as an El Niño event. Rather than returning to its pre-El Niño state, the lake recovers only slightly. “This has the effect of stepping up stairs toward becoming a different kind of lake,” she explains, “and at some point Lake Tanganyika will be forever changed.”

Both O’Reilly and McIntyre are members of the Global Lake Temperature Collaboration. They say more research is needed to determine how the lake’s resilience is being affected and whether it will recover from these step-like changes. Although the science is rapidly developing, they think it will be several years before researchers have the capability, assuming that needed data are available, of predicting how close the lake is to reaching a critical “tipping point.”

For the people living on inland lakes, this sounds like the equivalent of the apocalyptic scenarios for sea level rise and more intense storms we’ve all heard about and begun to see in coastal regions. And yet many sources of funding for research and conservation programs on Lake Tanganyika have fallen off in recent years.

Scientists are concerned that Lake Tanganyika is nearing a ‘tipping point’ where changes become permanent. Photo by Catherine O’Reilly.

What the Future Holds

By studying Lake Tanganyika, not only do scientists learn more about how climate change is affecting one of the world’s largest, deepest, and oldest lakes, their interdisciplinary research provides tremendous insight into how warming trends affect the entire planet, from the tiniest microscopic organisms and schools of colorful fish to the top of the food chain: we humans ourselves.

The four riparian nations surrounding Lake Tanganyika are committed to taking action, but they sorely lack financial resources to get much done. Government representatives met in February 2012 under the auspices of the Convention on the Sustainable Management of Lake Tanganyika and renewed their commitment to an updated Strategic Action Programme. They also pledged to embark on an international fundraising campaign to secure funds for the conservation and management of the lake’s rich natural resources.

Dried sardines for sale in a market on Lake Tanganyika. Photo by Catherine O’Reilly.

Recognizing the impacts of a warming climate, The Nature Conservancy (TNC) launched a project in 2012 with other local and international partners, which includes establishing effective climate change adaptation strategies and actions in the Lake Tanganyika region. The Tuungane (Kiswahili for “let’s unite”) project uses a participatory approach and is based “on the premise that the most effective way to combat climate change is to empower the local communities to sustainably manage their own resources.”

According to Colin Apse, a senior freshwater adviser at TNC, most of these actions do not involve radical departures from actions people are already taking to improve their livelihoods and economies and to protect the ecosystems they depend on. He says there is a wide range of adaptation strategies available, such as implementing village land use plans, improving fisheries practices, and limiting further habitat destruction. Apse is hopeful that these and other strategies can help the people living around Lake Tanganyika prepare for a rapidly changing future.

Lake Tanganyika fish serve as a major source of protein for millions of people living around the lake. Photo by Catherine O’Reilly.

Unlike retreating glaciers, there is actually something that can be done to lessen the impacts of climate change in lake regions. By recognizing climate change as a major factor, not only for how it affects the health of the lake but the welfare of the people living around it, researchers and conservationists working on Lake Tanganyika are already leading the way forward.

Lisa Borre is a lake conservationist, freelance writer, and avid sailor based in Annapolis, Maryland. With her husband, she co-founded LakeNet, a world lakes network, and co-wrote a sailing guide called “The Black Sea” based on their voyage around the sea in 2010. She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program in the 1990s.

A new environmental threat map of the Great Lakes shows cumulative stress is highest in Lakes Ontario, Erie and Michigan, especially along the shoreline and near busy harbors. Source: Great Lakes Environmental Assessment and Mapping (GLEAM) Project.

A new environmental threat map of the Great Lakes serves as a powerful visualization tool for those interested in the challenges facing lake restoration efforts. The map brings to mind the adage, “a picture is worth a thousand words.” But the colorful image is worth even more than that – the red, orange, and blue colors on the map show multiple stressors and represent gigabytes of data from decades of research. It paints an alarming picture about the cumulative effect of stress on such a precious freshwater resource.

The comprehensive map is the product of the Great Lakes Environmental Assessment and Mapping (GLEAM) project. Led by researchers at the University of Michigan, the group published a paper about the ambitious project in last week’s print edition of the Proceedings of the National Academy of Sciences. They also produced a cool interactive mapping tool which is now available on the GLEAM project website. Privately funded by the Erb Family Foundation, the main results of the project are summarized in a press release and were reported in news outlets throughout the Great Lakes region. I recently spoke with several members of the research team to learn more about the project.

“We found that the places where people gain the most benefit from a healthy lake ecosystem are also the ones with the highest levels of stress,” the project’s lead researcher and a professor of aquatic sciences at the University of Michigan’s School of Natural Resources and the Environment, David Allan, told me. “Marinas, boating activities, and public beaches tend to be near population centers where environmental stress also tends to be greatest.”

In addition to a cumulative stress index map, the research team generated separate digital maps for 34 individual lake stressors. Like a digital photo, the maps are made up of individual pixels. One pixel on the map represents one square kilometer of lake surface area. For 94,000 square miles of lake surface area, that’s 34 layers of information for each of the 244,000 pixels that make up the map. For all of its complexity, the visual display is clean and simple.

“Our intent in developing these maps was to give a bird’s eye view of which regions are the most stressed and which regions suffer from a particular stress at the highest levels,” said Peter McIntyre, a co-author of the study and professor at the University of Wisconsin-Madison’s Center for Limnology. “This view from 30,000 feet is most meaningful for making regional comparisons among lakes and for drawing conclusions about the state of the environment at very broad spatial scales.”

While the maps also provide useful perspective for restoration at a more local level, there is a risk of over-interpreting the data depending on how finely you zoom in, especially if viewing individual pixels near color boundaries. “These maps are just one important input into a process informed by local knowledge and additional data gathering,” Allan said.

The lake temperature map shows Lake Superior, one of the most rapidly warming lakes in the world, at highest risk. Source: Great Lakes Environmental Assessment and Mapping (GLEAM) Project.

What the Maps Say About Climate Change-Related Stressors

With recent concern about the role of climate change in exacerbating problems on the Great Lakes, including record low water levels on Lakes Michigan and Huron last month, I was particularly interested in this part of the research team’s analysis.

As with many of the lake stressor maps, the climate change data is displayed in a way that hasn’t been available to date. A quick glance at the warming lake temperature map shows Lake Superior, one of the most rapidly warming lakes in the world, at highest risk. The ice cover map shows the greatest loss in ice cover along the shorelines of the upper Great Lakes, especially in large bays like Grand Traverse Bay, Georgian Bay and on Lake Superior.

Sigrid Smith, a postdoctoral researcher at the University of Michigan, coordinated most of the analysis of the map data. She explained that the water level map is more rudimentary compared to the other two climate maps. “Using bathymetry maps, we simply identified areas of the lake that are less than three meters deep because these will be most susceptible to abnormal fluctuations in water levels,” Smith told me. Compiling the other maps involved serious number crunching to look at real trends. “We used sophisticated computer programming to analyze trends in lake temperature and ice cover from daily snapshots over a couple decades,” she said.

Decreasing ice cover has been along shorelines and in large bays of the upper Great Lakes. Source: Great Lakes Environmental Assessment and Mapping (GLEAM) Project.

How Well Do the Maps Reflect Reality?

If you think in terms of maps as I do, you may find yourself clicking and zooming around the online maps to find out what they say about your favorite beach, boating harbor, bird watching area or fishing hole. Although the research team cautioned me about interpreting the data at the finer end of the scale, I couldn’t resist zooming in to see what it had to say about a stretch of beach I visited on northern Lake Michigan on a cold, windy day in late November.

Hundreds of dead loons have been found on northern Lake Michigan beaches. Photo by Lisa Borre.

First, let me explain the backstory for the photo above. Friends of my family told me of the beach on the Leelanau Peninsula where they had found dead loons and cormorants. I had read an online article in the Detroit Free Press about this tragic die-off and felt compelled to see the evidence with my own eyes.

Finding the frozen carcass of such a majestic bird saddened me beyond words. The story about how such a large water bird – and hundreds like it – ended up on this frigid stretch of rocky coastline read more like a sci-fi novel than a wildlife specialist’s account.

A bizarre set of interactions sealed the loon’s fate. Experts believe that invasive zebra and quagga mussels play a role, by creating suitable conditions for a particular species of algae to thrive. It now grows in mats and in deeper water along the lakeshore. When the mats of algae decompose, oxygen in the water is depleted, and botulism bacteria thrive. Invasive round gobies are well adapted to the new conditions, and they pick up the deadly bacteria, which gets passed up the food chain to the fish-eating loons and cormorants. They then die en masse and wash up on beaches.

Some of the environmental stressors that led to this nightmare scenario are now viewable with the online maps. I was not surprised to find that this area of the lake shows up in red on the cumulative stress map, indicating that it is under high stress compared to the rest of the lakes. I then zoomed in on the stretch of shoreline where I snapped the photo and viewed the individual lake stressors there.

A zoom of the cumulative stress index map shows nearshore areas at some of the highest threat levels for all of the Great Lakes. Source: Great Lakes Environmental Assessment and Mapping (GLEAM) Project.

The likely suspects causing the loon’s death seemed to correspond quite well with the lake stressor maps. This area of the lake shows up red and orange on two of the key invasive species maps, indicating that it is on the medium-high to high end of the stress index for round goby and for zebra and quagga mussels. All are suspected culprits contributing to the loon’s death. The maps also identify this part of Lake Michigan as an important area for fisheries, which is why the loons use it as a feeding ground.

In total, the maps showed that 12 of the 34 lake stressors were medium to high on the stress index scale for this one stretch of Lake Michigan coastline. The cumulative stress index map and my photo of the dead loon tell a similar story: the Great Lakes coastline is not only important to humans and wildlife but is under tremendous environmental stress.

Global Context

High-resolution threat mapping is a technique that’s been used by groups concerned with the world’s oceans and river basins. The GLEAM project is the first time a similar approach has been used to cross-compare environmental stressors and the ecological services provided by lakes.

I asked the team about the applicability of the threat mapping approach for other lake regions. Allan says that it is a generalizable approach that can easily be used elsewhere. McIntyre added that there is a blessing and a curse when placing this study in a global context. “We are blessed to be working in one of the most data rich large lake regions of the world,” he said. “The curse is that we have an immense number of stressors, most of which are not at all unique to the Great Lakes of North America.”

Shoreline along Leelanau Peninsula on northern Lake Michigan in November 2012. Photo by Lisa Borre.

Implications for Great Lakes Restoration Efforts

The team intends for their expansive research effort to help guide future Great Lakes restoration efforts, including the federally funded Great Lakes Restoration Initiative (GLRI) underway since 2009. For the most part, GLEAM researchers found current investments are going to the areas with the highest levels of environmental stress, but they are quick to point out how their maps create opportunities for a more strategic approach to considering future investments.

In addition to helping target specific places, McIntyre explained that the maps could help broaden the portfolio of restoration efforts. “By quantifying each lake stressor independently and placing them on an even playing field in terms of spatial data, our maps highlight the full range of stressors in a given area,” he said. “In some cases, restoration projects may be designed to alleviate only a handful of the few dozen threats that are at moderate to high levels.” He suggests that the maps could point out whether there is still a substantial “to do” list for existing restoration sites.

Another way the maps can be used is to complement restoration initiatives by identifying low-stress sites, places where fewer of the more challenging problems need to be dealt with but where human benefit is also high. “Our first round of analysis helps set the stage for a more systematic and strategic approach to restoration investments down the line,” McIntyre said.

Although the bi-national project team included representatives of some of the federal agencies involved with the GLRI, it’s too early to evaluate how the maps will influence the overall restoration program. Several conservation groups, however, were involved in the project and have already embraced the threat mapping approach, including regional projects of The Nature Conservancy and National Wildlife Federation.

Sometimes a map confirms your thinking about what you see at ground level, and other times, it can challenge your understanding of the world around you. The new environmental threat map for the Great Lakes did both for me. Having grown up in the region and sailed on all five lakes, I would have used a red marker to color many of the areas that the research team found to be high stress. But the precise nature of the patterns created on their maps, backed up by data and careful analysis, was as eerie as the call of a loon on a calm lake after dark. It startled me to see how much of the Great Lakes shoreline is under high stress and how few areas are relatively stress-free.

Record low water levels and dead loons washing up on the beach are two of the more visible indicators of a stressed ecosystem. These events, along with the new map showing the cumulative effect of multiple stressors, create a sense of urgency for the success of Great Lakes restoration efforts. Perhaps in addition to identifying the areas at greatest risk, the new maps will also help guide the way forward.

Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, MD. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-wrote a sailing guide called “The Black Sea.” She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program in the 1990s.

Water levels reached record lows for the month of December on Lakes Michigan and Huron. Photo by Lisa Borre.

It looks like low water levels on the Great Lakes will be added to the record-breaking climate-related events of 2012.

The water level on Lakes Michigan and Huron dropped another 2.5 inches (6 cm) in December, unofficially breaking a nearly 50-year-old record for the month. Last month’s average for both lakes – considered one lake for the purposes of hydrologic studies because of the connection at the Straits of Mackinac – was 576.15 feet, according to the U.S. Army Corps of Engineers (USACE) water level report. This is about a half-inch below the record for the same month set in 1964 since the USACE began keeping coordinated records in 1918.

Lake Superior continues to hover about six inches (16 cm) above record low water levels set in 1925. USACE forecasts for all of the Great Lakes predict that water levels will remain below the long-term average for the next few months.

As explained in a previous post about how climate change and variability affect low water levels on the Great Lakes, evaporation normally exceeds precipitation and runoff at this time of year. Human-induced climate change is likely making a bad situation worse by affecting factors that control water supply to the Great Lakes, including a severe drought in 2012, warming water temperatures, increased evaporation rates, loss of ice cover, and changing precipitation patterns.

Lake Lillinonah in western Connecticut on a pleasant day in late August 2007. Photo by Tod Osier.

A named tropical storm had dramatic effects on a group of aquatic ecosystems last year, but the affected waters were not what you might expect. They were freshwater lakes and reservoirs spread across the northeastern U.S. and southeastern Canada, some located far inland from the coast. A new study sheds light on the consequences of these extreme events for inland waters across the globe.

When Hurricane Sandy struck the northeastern U.S. at the end of October, another powerful storm had yet to fade from memory. How could anyone forget the widespread power outages and images from Irene that showed historic covered bridges washing down rivers in Vermont or air photos of muddy water filling national treasures like the Chesapeake Bay, Hudson River, and Lake Champlain?

The nature of the impacts of the two storms couldn’t have been more different. Sandy caused extensive damage to densely populated areas along the coast, making it one of the most devastating storms to make landfall in the U.S. Irene, on the other hand, unleashed its fury further inland, bringing severe flooding to areas as far north as the St. Lawrence River Valley in Quebec.

With extreme weather events expected to increase as the climate warms, studying the ecological effects of these storms takes on new importance. The past focus has been on the damage to coastal areas, but as Irene has taught us, impacts to inland waters are also a concern. This is why researchers from lakes affected by the 2011 storm teamed up to see what they could learn about its effects.

The unique study was possible because scientists had previously deployed automated sensors in nine lakes situated in a variety of landscape settings across the affected region. Local lake associations and New York City’s water supply program use the high-tech devices to help inform management decisions. Researchers who study these lakes were already collaborating as members of the Global Lake Ecological Observatory Network (GLEON).

The automated sensors are mounted on buoys and measure the effects in real-time. During Irene, they collected data from each lake every ten minutes to six hours, depending on the lake. The high frequency data, combined with the network of citizens and scientists observing the lakes and long-term monitoring records, allowed them to make new observations about the effects of extreme weather events.

The GLEON buoy on Lake Sunapee in New Hampshire was used to monitor the lake before, during and after Irene. Photo by Lisa Borre.

Using buoy data to compare the impacts of Irene was the brainchild of Kathleen C. Weathers, senior scientist at the Cary Institute of Ecosystem Studies and co-chair of GLEON. Her family has long ties to Sunapee, so she also serves as research director for the Lake Sunapee Protective Association (LSPA) and was instrumental in helping the group establish a monitoring buoy in the lake.

“The high frequency data from GLEON buoys are ideal for making cross-lake comparisons,” Weathers said. “Not only can citizens and scientists learn more about their own lake, they can compare results with researchers working on other lakes around the world and therefore contribute to regional- and global-scale studies, which is a remarkable opportunity.”

Several years ago, Friends of the Lake, a local citizens group on Lake Lillinonah, Connecticut’s second largest lake, invited Jennifer L. Klug, a lake scientist and associate professor at Fairfield University, to collaborate with them. Together they set up a research and monitoring program that uses sensors mounted on a buoy and an onshore weather station and includes a role for citizen scientists. It’s a win-win for all involved. “Friends of the Lake gets information they need about the lake, I can get my students involved in relevant research, and the data can be shared as part of an active global network,” Klug told me.

“We started from scratch a few years ago,” said Klug. “LSPA and GLEON members gave us invaluable advice as we designed and deployed our monitoring program.”

The results of the nine-lake study were published recently in Environmental Science & Technology. Klug, the lead investigator, told me that this may be the first time scientists have conducted a cross-lake comparison using high frequency data for a single storm event anywhere in the world.

When Irene made landfall in New York in 2011, sensors mounted on a buoy quietly measured its impact to the usually tranquil waters of Lillinonah. Nestled in the granite bedrock of western Connecticut, the lake was created in 1955 by impounding the Housatonic and Shepaug Rivers. Technically a reservoir, the lake is a popular spot for fishing and boating and loved by the residents living along its shores.

Further north on Lake Sunapee in New Hampshire, staff and volunteers at the local lake association braced for the storm while their buoy recorded the lake’s vital signs every 10 minutes. The effects of the storm can be seen in a report on the LSPA website.

Lake Sunapee and other lakes in the study recovered relatively quickly in a physical sense. Photo by Lisa Borre.

Both lakes were located just east of the storm’s track. Other lakes in the study were located on or west of the storm’s track. Even Onondaga in New York and Croche in Quebec, two of the furthest away, felt the effects of rain and wind produced by Irene. Ashokan, Rondout, and Kensico Reservoirs, part of the New York City Water Supply, and Lake Lacawac in Pennsylvania, received the heaviest rainfall.

On August 27, Hurricane Irene made its first landfall in North Carolina and then weakened to a tropical storm as it passed the mouth of the Chesapeake Bay. It was the last full day before the effects of the storm were felt inland in the Northeastern U.S. The buoys on all lakes in the study reported relatively stable conditions. The lakes had yet to begin fall turnover, an annual event where the surface water, warmed by the summer sun, mixes with cooler, denser water underneath.

Irene’s wrath was unleashed the following day when the storm reached its maximum intensity for all of the study lakes except Simoncouche, in Quebec. Within hours, the temperature profiles, as measured every meter or so from the top to the bottom, for all of the lakes were disrupted.  Thermal stratification, a characteristic of most north-temperate lakes during the summer and early autumn, is important because it controls fundamental aspects of lake chemistry and the distribution of organisms.

What was interesting is that Simoncouche was one of the most affected by the storm, and a reservoir right under the storm’s track near New York City was one of the least affected.  The reason for this, according to the study, was mainly due to both the intensity of the storm and the size of the watershed relative to the volume of the lake. The larger the land area contributing water to the lake and the greater the intensity of the storm, the more disruption within the lake itself. Although it received some of the heaviest rainfall, Kensico Reservoir has a relatively small watershed compared to the other study lakes.

“The most heavily impacted lakes were the ones that received a lot of rain and have a large catchment area,” Klug told me. As the rain falls on the watershed, it flows down through the rivers and streams and eventually reaches the lake. “This was the major mechanism for disrupting the physical stability of the lakes,” she said. “It is also what delivers high levels of sediments, phosphorus, and other unwanted materials to the lake as they wash from land to water.”

The good news is that the lakes recovered relatively quickly in a physical sense. “All but one of the lakes was back to 80% of their pre-storm stability within a week,” Klug said. These are the kind of conclusions that scientists can only reach by comparing effects on a group of lakes in different settings. She added, “We never would have been able to figure that out without the high frequency buoy data.”

I visited Lake Sunapee on a rainy day about six weeks after the storm and can attest to how normal the lake appeared on the surface. I was participating in a GLEON-organized field trip and used my smartphone to connect with the dashboard displaying buoy data on the LSPA website. It was immediately apparent how the temperature and dissolved oxygen in the lake were affected by the same autumn-like conditions I felt at the surface that day.

A sediment plume flows into New York harbor from the Hudson River after Hurricane Irene. Photo credit: NASA.

Of greater concern are the lasting effects from the flush of materials washed off the land and into the lakes. In Ashokan Reservoir, runoff from the clay-rich soils in the surrounding watershed turned the water muddy brown in color. It looked more like a café latte than part of New York City’s water supply system. “Turbidity in the reservoir following Irene was some of the highest recorded, and remained elevated for more than eight months following the storm,” the study states. “Loading models using high frequency sensor data directly influenced active management of the water delivery system,” the report explains. By understanding what parts of the system were affected, managers were able to continue delivery of high quality drinking water to consumers without interruption.

Algae blooms plague Lake Lillinonah in late August. Photo by Tod Osier.

On Lillinonah, citizen scientists measured the levels of phosphorus before and after the storm. This nutrient is a particular concern in lakes because it contributes to algae blooms. “Phosphorus levels more than doubled after the storm,” Klug told me. She noted that some of the phosphorus eventually may have ended up further downstream, but some likely ended up being retained by the lake. Further complicating matters is a proliferation of zebra mussels in 2012. The tiny molluscs are particularly adept at filtering water and might explain why water quality measurements this past summer were some of the clearest on record. As a result, the group may never now what can be attributed to the storm. Although the lasting effects may be more difficult to determine, Klug said, “The main factor controlling this is the length of time water resides in the lake.” She believes this is why long-term monitoring programs are also important.

Citizen scientists are actively involved in research on Lake Lillinonah. Photo by Jennifer Klug.

Another factor affecting the lakes was the timing of the storm. In the case of Irene, it was near the end of the summer season. Had the storm event occurred earlier in the year, it might have caused a major disruption to the biology of the lakes as well. Klug told me that Lillinonah didn’t have any algae blooms after the storm, in part because the turbid water reduced the amount of light available for aquatic plant growth. She also hypothesized that some of the algae was simply washed out of the lake during the storm.

“Unlike fallen trees, downed power lines, and coastal flooding, the effects of extreme storms on inland aquatic systems are less visible but no less real,” said Klug. She believes that it is all the more reason for lake groups to do what they can to protect the watershed. “The better the land is managed around the lake, the less unwanted material will wash into the lake during a storm event.”

Hurricane Sandy occurred much later in the season. Most of the lakes had already completed fall turnover. The monitoring buoys had been pulled for the winter earlier in the month. The lakes were spared the drenching rains this time, but as a result of the work by Klug and her colleagues, the people who care about these and other lakes will have a better understanding of what can be done to lessen the impact of the next storm that comes along.

Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, MD. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-wrote a sailing guide called “The Black Sea.” She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program in the 1990s.

Low water levels expose the sandy lake bottom on Lake Michigan. Photo by Jeff J. Cashman.

For people living around the Great Lakes, water levels this past month have appeared much lower than many will remember. The upper Great Lakes reached near-record low water levels in October. This was most evident on Lakes Michigan and Huron, where lake levels dropped to less than two inches (4 cm) above record lows and 28 inches (71 cm) below the long-term average. All five lakes, plus Lake St. Clair, remain below their long-term averages.

Rock and sand recently exposed by low water levels made stretches of the northern Lake Michigan shoreline look like a moonscape. Recreational boaters had trouble navigating the shallow water this fall, and shipping companies lightened loads to compensate for low water. Lakes Michigan and Huron hovered just above a record low set nearly 50 years ago, and Lake Superior was within five inches (11 cm) of a record low set in 1925.

A 2002 National Geographic magazine story, Down the Drain: The Incredible Shrinking Great Lakes, documents declining lake levels and the potential economic and ecological consequences for the region. Ten years later, the story continues to unfold, as water levels remain lower than normal.

Experts blame the recent low water on the unusually warm and dry weather over the past year. Rain events in October, including Hurricane Sandy, delayed the inevitable, but forecasters predict Lakes Superior, Michigan, and Huron will likely reach historic low levels in the late fall or winter, a time of year that the lakes are normally already dropping due to high rates of evaporation.

Water levels on Lake Michigan were within two inches of record lows in October and are expected to continue dropping as part of the normal seasonal decline through fall and winter. Photo by Jeff J. Cashman.

Low water levels are not the only climate-related trend being observed on the Great Lakes. Ice cover is also declining. The Great Lakes have lost 71% of their ice cover since 1973, according to a study by the Great Lakes Environmental Research Laboratory (GLERL). This past winter, the Great Lakes, including Lake Superior, were virtually ice free with just 5% ice coverage, the second lowest on record. Similar to the global assessment conducted in 2000, loss of ice cover is being reported on lakes throughout North America, Europe, and Asia.

Lake Superior is one of the most rapidly warming lakes in the world.

Summer lake temperatures are also on the rise. As mentioned in one of my previous posts about warming lakes, the Great Lakes are among many lakes in the northern hemisphere experiencing a rapid warming trend. Lake Superior, the largest freshwater lake in the world by surface area and third largest by volume (after Baikal in Siberia and Tanganyka in Africa), is also one of the most rapidly warming lakes in the world.

Because lower lake levels are considered one of the potential consequences of climate change, I was curious to find out whether there was any connection to what is being observed on the Great Lakes.

I recently had the opportunity to talk with John Lenters, a lake and climate scientist, while we attended a meeting of the Global Lake Ecological Observatory Network (GLEON) in Mulranny, Ireland. When comparing notes about our personal connections to Lake Superior, I learned that this accomplished scientist, with a laid-back, Midwestern manner, first fell in love with the Big Lake as a 14-year-old boy while on a backpacking trip in Isle Royale National Park. “Although the trip was grueling, I was awed by Lake Superior and realized I wanted to study lakes,” Lenters told me.

Now an associate professor at the University of Nebraska–Lincoln (UNL), Lenters studies lake-climate interactions in the Great Lakes region, the Alaskan Arctic, and western Nebraska. Given the global implications of his research, he joined GLEON in 2008 and helped to form the new Global Lake Temperature Collaboration (GLTC), hosting their first meeting at UNL this past June. With his boyhood dream as inspiration, he and his collaborators are leading the way to learning more about how climate change is affecting lakes around the world, including the Great Lakes.

Sunset on Granite Island, Lake Superior. Photo by John Lenters.

On Lake Superior, Lenters and his collaborators are studying the interactions among evaporation, ice cover, and water temperature. Their research builds on work by others in the region (and elsewhere) and provides new insight on factors affecting water levels.

Surface Water Temperatures Increasing on the Great Lakes

Similar to Lenters’ findings in a 2004 paper, which found Lake Superior to be warming more rapidly than summer air temperatures, Jay Austin (a GLTC collaborator) led a study of lake temperature trends at the University of Minnesota-Duluth’s Large Lakes Observatory (LLO). Published in Geophysical Research Letters, the LLO study found that summer surface water temperatures on Lake Superior have increased approximately 4.5°F (2.5°C) during the period 1979–2006.

The LLO study found that the decline in winter ice cover leads to an earlier start of the summer stratified season, a natural process in lakes when water near the surface warms, while deeper waters remain a more constant, cooler temperature. The earlier the lake becomes stratified in summer, the longer the warming period. “This results from a progressively earlier start of the summer stratified season, in response to a significant decline in average winter ice cover,” the study states. “Given a longer summer stratified season, surface waters can be heated to higher temperatures than that expected from increases in air temperature alone.”

Researchers also found a clear relationship between ice cover and summer water temperatures, which tend to be cooler following a winter with extensive ice cover. In contrast, winters with less ice cover tend to be followed by a summer with warm surface water temperatures. This is exactly what happened this year on Lakes Superior, Michigan, and Huron. The lakes were relatively ice free in 2011–12 and reached record-high water temperatures in the summer.

New Insight About the Interaction Between Ice Cover and Evaporation

Measuring evaporation rates on lakes as large as Superior is a very difficult and intensive process, so until recently, researchers in the Great Lakes region relied on models instead. The models correctly account for the various factors that impact evaporation rates, including when the lake surface is covered by ice. But with ice cover shrinking on all of the Great Lakes, scientists began to wonder what impact this would have on observed evaporation rates. Understanding this new dynamic required the installation of new monitoring stations on all five of the Great Lakes. Results are being shared through a network of researchers monitoring evaporation rates.

Lenters and his collaborators established a monitoring station on Granite Island in Lake Superior to measure evaporation rates. Photo by John Lenters.

In the past, experts assumed that as ice cover decreased, evaporation would increase, since more of the lake’s surface is exposed to the air during winter months. But a new paradigm is emerging.

“Some of our recent work challenges the standard paradigm that more ice cover means less evaporation,” Lenters told me. Evaporation rates are increasing as the climate changes, but the relationship to water temperature and ice cover is not as simple as previously thought.

Katherine Van Cleave, Lenters’ former student at UNL, recently completed a study of these interactions for her master’s thesis. Her study includes an analysis of the first direct observations of nearshore evaporation rates on the Great Lakes, using a high-tech monitoring station on Granite Island, near Marquette, Michigan. She also looked at some of the primary climatic factors driving this variability. Although her study period, from October 2010 to April 2012, does not include this past summer, the impact of the warm 2012 water temperatures on evaporation rates is entirely consistent with her findings.

Scientists use high-tech equipment to monitor evaporation from Lake Superior year-round. Photo by John Lenters.

Research by Lenters at Granite Island and a study with other collaborators at Stanard Rock (published in the Journal of Great Lakes Research) has examined seasonal and annual evaporation rates on Lake Superior. Together with research by Van Cleave, they found that evaporation rates in late winter and early spring (when ice cover is typically at a maximum) are generally minimal, even in years with low or no ice cover. The highest rates of evaporation, on the other hand, occur during the fall and early winter and, during particularly cold years, can actually lead to greater ice cover later in the winter and spring. “Evaporation is a cooling process,” explained Lenters, “and the more rapidly it occurs, the more likely the lake is to reach freezing temperatures and form extensive ice cover.”

Evaporation from a lake is similar to how we humans perspire to cool our bodies on a hot summer day. It is a process that transfers heat from the lake back into the atmosphere. When a lake evaporates, heat is released to the atmosphere. The more the lake “sweats,” the more it cools.

So instead of simply thinking of ice cover as a “cap” on evaporation, we need to realize that the reverse is also true – that strong evaporation can lead to high ice cover. In other words, says Van Cleave, “this ‘standard paradigm’ of decreasing ice cover, increasing water temperatures, and increasing evaporation may not stand as a full explanation of the role of evaporation in these processes. More evaporation in the fall will cool the lake quicker, leading to an earlier onset of ice cover.”

The Great Lakes, including Lake Superior, were nearly ice free during the winter of 2011-12. Source: NASA MODIS satellite photo from NOAA Great Lakes Coastwatch website.

But the lack of ice cover affects evaporation in another important way – by impacting water temperatures and evaporation rates much later in the year. “Ice cover was found to be a strong determinant of summer water temperature, and this in turn, can lead to changes in late-summer evaporation rates,” Van Cleave concluded.

Regime Shifts in the Great Lakes Ecosystem

Van Cleave found a regime shift in the Great Lakes ecosystem after extreme climate conditions in 1997-98. Photo by John Lenters.

Van Cleave made an interesting discovery after looking at long-term data for Lake Superior: Certain changes have not been linear through time. Scientists use statistical analysis to see if patterns emerge in their data and to determine whether certain parameters are increasing or decreasing with time. “Lake Superior experienced a pronounced change during the winter of 1997–98 when ice cover reached, at the time, record low levels,” her report states. “This was followed by record-warm summer water temperatures and near-record evaporation rates (surpassed only by 1987).”

“A step-change occurred in 1997–98 that resulted in a drop of ice duration of nearly 40 days, a 5.4°F (3°C) increase in summer water temperature, and a near doubling of July-August evaporation rates,” Van Cleave concluded. Ecologists refer to an abrupt change such as this as a regime shift, and although some evidence indicates that the lake recovered somewhat, Van Cleave found that these more recent trends ”are not statistically significant, suggesting that the 1998 regime shift has largely been sustained.”

Given the extreme conditions of this past year, Lenters wonders whether Lakes Superior, Michigan, and Huron are in the midst of another such regime shift.

Lake Levels Remain Below the Long-term Average

The U.S. Army Corps of Engineers (Corps) began keeping coordinated water level records in 1918. They base “record events” on calculations of monthly average lake level. Lake Michigan-Huron, considered one lake for hydrological studies because of the connection at the Straits of Mackinac, was 576.6 feet (175.74 meters) above sea level in October. The all-time record low for all months occurred in March 1964, when the lake dropped to 576.0 feet (175.58 meters).

The Great Lakes Water Level Dashboard, a handy, interactive online tool provided by NOAA, helped me to better visualize historic water level trends going back to 1861. I was reminded of a period of high water on the upper lakes during the 1970s and 1980s, when everyone was concerned about erosion along the lakeshore and houses were falling into Lake Michigan. What also jumped out are the below-average water levels after the 1997–98 event that Van Cleave described.

Screenshot of NOAA's Great Lakes Water Level Dashboard showing Lakes Superior (top) and Michigan-Huron for the period 1918-2012.

Great Lakes water levels normally fluctuate throughout the year and from one year to the next depending on climate conditions. The lakes naturally cycle between periods of high water and low water, but abrupt changes in annual water levels are not unusual. These fluctuations are due to climate variability and are considered vital to a healthy ecosystem.

One variable the Corps constantly monitors is the supply of water to each Great Lake, which is made up of rainfall on the lake surface, runoff to the lake, and evaporation from the lake. In a teleconference with the media, Keith Kompoltowicz, chief of the Watershed Hydrology Branch in the Corps’s Detroit District Office, explained that this supply is the primary driver of water level fluctuations and that this past year, evaporation was much greater than precipitation and runoff combined. “Any time there is a scenario like that, lake levels will likely decline,” he said.

Lake levels are expected to continue dropping as part of the normal seasonal decline through the fall and winter. “Evaporation usually wins out at this time of year,” said Kompoltowicz.

Near-record low water levels on Lakes Michigan and Huron in October hovered just above a record low set nearly 50 years ago. Photo by Jeff J. Cashman.

Lakes Superior, Michigan, and Huron have been fluctuating below average levels since the extreme event 15 years ago. Corps officials acknowledged that the upper lakes have not recovered from this extreme event and are not likely to anytime soon. “We would need several months and seasons in a row of very wet weather to get us back to long-term average,” said Kompoltowicz.

This extended period of low water raises questions about whether climate change is contributing to declining lake levels, but the Corps maintains the position that it’s difficult to know, because the lakes continue to fluctuate within their normal range.

Low Lake Levels Renew Debate About Potential Causes

Controversy usually arises about potential causes whenever lake levels are low. Numerous theories abound. People ask whether a diversion in Chicago to the Mississippi River watershed might be to blame. Others point to erosion or dredging in the St. Clair River. John Allis, Chief of the Corps’s Great Lakes Hydrology and Hydrography Office, dismissed these claims, citing studies that show the Chicago diversion is more than offset by a diversion into Lake Superior from Canada.

Allis referred to a study of historic dredging and sand removal operations on the St. Clair River. “Studies show that the net impact of historic dredging and erosion is about 10 to 15 inches lower water levels in Lakes Michigan and Huron,” he said. “The last dredging project was completed in the 1960s, and since 1967, the only dredging that has been done on the St. Clair River is maintenance dredging to keep the rivers at authorized depths.”

The St. Clair River flows from Lake Huron to Lake St. Clair and the Detroit River. Historic dredging and sand removal projects resulted in water levels that are 10 to 15 inches lower on Lakes Michigan and Huron. Photo by Lisa Borre.

The Corps says that when water levels are low, they get asked about whether structures could be built to restrict flow in the St. Clair River. “Recent studies show that any of those projects could range from $50–200 million to construct,” said Allis. “Although water is low right now, there are many groups that would not support the construction of structures because of concerns about what would happen in high water.” He explained that projects to mitigate historic water losses were de-authorized in the late 1970s when the lakes approached record high levels.

The International Joint Commission (IJC) studied the impacts of dredging and erosion in the St. Clair River on water levels in the upper Great Lakes. Among other things, the International Upper Great Lakes Study (IUGLS) evaluated remedial measures for historic dredging projects and erosion. “The Study Board found that there had been some erosion in the St. Clair River between 1962 and 2000, but the riverbed had stabilized since then, making it unclear whether action would be appropriate,” said IJC Public Information Officer John Nevin. Further details can be found in the summary report.

Ships on the Great Lakes have lightened loads this fall due to low water levels. Photo by Lisa Borre.

The five-year, $14.6 million study by the Study Board also examined options for regulating water levels and flows in the upper Great Lakes system, consistent with the Boundary Waters Treaty of 1909. In March, the Study Board released its final report and recommended a new regulation plan for Lake Superior outflows, one that is “more robust than the existing plan and provides benefits, especially to the environment,” said Nevin. The new plan will not change regulation in a way that helps the situation on Lakes Michigan and Huron. “If we were to try to do that, it would damage Lake Superior,” he said. “It really can’t be done.”

A new regulation plan for Lake Superior will make it easier for ships transiting the Soo Locks and improve spawning habitat for endangered lake sturgeon in low water conditions. Photo by Lisa Borre.

The focus on past diversions and dredging operations is not surprising, given the complex nature of more subtle but very real changes underway. I asked Lenters for his opinion on other theories that explain why the lakes are so low this year. “No one bottled it up and took it away or diverted it to the Mississippi,” he said. “Together with the low precipitation we’ve seen this year, the lake water simply evaporated more quickly.”

Management Agencies Study Effects of Climate Change

With nearly 20% of the world’s surface freshwater at play and millions invested in restoration efforts, the stakes are incredibly high for understanding how natural climate variability and human-induced climate change affect the Great Lakes.

The IUGLS evaluated the impacts of climate change on lake levels in the Great Lakes region with state-of-the-art climate research. Projections suggest that “lake levels are likely to continue to fluctuate, but still remain within a relatively narrow historical range – while lower levels are likely, the possibility of higher levels cannot be dismissed.” Nevin explained it another way. “Low lake levels are not a new normal,” he said. “We expect to see lake levels fluctuate as we have in the past.”

State-of-the-art climate research conducted as part of the International Upper Great Lakes Study indicates that increased evaporation due to climate change will be largely offset by increases in local precipitation in the Lake Michigan-Huron basin. Photo by Lisa Borre.

The IUGLS acknowledges that despite uncertainties in the models used, “it is clear that evaporation is increasing and likely will increase for the foreseeable future.” The study further states, “Analysis indicates that in the Lake Michigan-Huron basin this increased evaporation is being largely offset by increases in local precipitation.” The outlook for Lake Superior is more cautious:

“In the Lake Superior basin, however, increasing evaporation over the past 60 years has not been compensated for by increased precipitation. As a result, the water supply has been declining in general in the basin. This trend is consistent with the current understanding of climate change. Unless changes in the precipitation regime occur, which is possible, [net basin supply] in Lake Superior will continue to decline, on average, despite the possibility of higher supplies at times.”

Experts predict that Lake Superior water levels will continue to decline, on average, due to increased evaporation rates caused by climate change. Photo by John Lenters.

These findings convinced the Study Board to recommend that “further climate analysis be undertaken to explore these dynamics” in order to provide more certainty in water supply estimates. Will changes in precipitation offset increased evaporation rates? Can lake levels recover from extreme events or are we seeing a new normal? These are some of the questions yet to be answered.

The IUGLS acknowledges that the Great Lakes basin is a complex system whose dynamics are only partially understood. In addition to further research, the Study Board recommends a more adaptive approach to future management – one that places climate change considerations in the mix. As the experience on Lake Tahoe shows, an important first step was acknowledging that climate change is a major driver in the ecosystem. Lake managers there are now focused on restoration projects that build the lake’s resilience to changes that are already underway.

Changes in ice cover, water temperature and evaporation indicate major shifts are underway on Lake Superior, the world's largest lake. Photo by John Lenters.

Lenters explained that this past year was like a “perfect storm” of conditions leading to high rates of evaporation and low water levels on Lake Superior. “Record low ice cover in 2011–12, an extreme heat wave in March, and a warm, dry summer led to record-high summer lake temperatures,” he said. “As a result, we saw higher-than-normal evaporation rates earlier in the season.”

Lake Superior evaporation – which is typically very low during spring and early summer – doesn’t normally begin increasing until early August. But this year it began as early as late June. Together with the summer’s below-normal rainfall, lake levels began their annual decline in the summer rather than in the fall. This would explain the near-record low lake levels in October. “Lake Superior’s rapid warming is like a canary in the coal mine,” Lenters told me. “We’re seeing changes in ice cover, water temperature, and evaporation that indicate major shifts are underway on the world’s largest lake.”

Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, MD. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-wrote a sailing guide called “The Black Sea.” She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program from 1990 to 1997.

Lake Tahoe. Photo by Brent Allen, TERC.

Lake Tahoe is one of hundreds of lakes around the world in the midst of a warming trend. The effects of climate change are starting to complicate efforts to maintain the lake’s relatively pristine state, putting Tahoe’s sapphire blue water and its overall ecological health at risk.

Surrounded by the Sierra Nevada Mountains and stunning scenery, the lake straddles the border between California and Nevada. At 1,645 feet deep, Lake Tahoe is one of the deepest lakes in the world. It is also one of the world’s oldest, at about two million years. Water resides in the lake for about six hundred years and flows out through only one outlet: the Truckee River.

The UC Davis Tahoe Environmental Research Center (TERC) released the Tahoe: State of the Lake Report 2012 in July.  According to the report, the Lake Tahoe region experienced extreme weather conditions in 2011, including one of the wettest and coldest winters on record. Given the local variability from one year to the next, researchers working on the lake benefit from an in-lake monitoring program that stretches back to 1968. This helps them put their results into the context of the long-term record.

Lake Tahoe warming at all depths

In 2006, researchers on Lake Tahoe became curious about whether they could find any climate change signal by looking at their long-term lake temperature data. “We undertook a study and saw warming of the lake at all depths,” TERC director Geoff Schladow told me.

The research team compared the results to a half dozen other lakes around the world and found that the warming rate was higher than some and lower than others. “We looked at the meteorological data and found that air temperatures had been rising for a hundred years,” he said. “That’s when it suddenly became obvious.”

The findings coincided with the year TERC produced its first annual State of the Lake report. Citizens in the Lake Tahoe region were shocked to learn that the lake was warming. Now six years later, climate change is considered a major driver for ecological changes occurring in the lake, along with urbanization and invasive species.

Extended lake stratification season a concern for water quality

The 2012 report notes that the length of time that the upper waters remain stratified has increased by almost 20 days, claiming that this is “a likely outcome of climate change.” During a typical summer the lake becomes stratified, with warmer waters on top and cooler water at depth. In the winter these layers mix, a process that refreshes the lake and keeps it healthy.

The extended stratification season on Lake Tahoe has major implications for water quality. “A longer stratification period increases the risk of losing oxygen at the bottom of the lake,” Schladow explained, “and this can release a huge, almost infinite supply of phosphorus to the lake in a process known as internal loading.” Phosphorus is the limiting nutrient in Lake Tahoe. The more there is, the more algae can grow, causing a decline in water clarity.

The length of time Lake Tahoe remains stratified has increased by almost 20 days, a likely outcome of climate change. Source: TERC.

Scientists predict that other more subtle changes may cause additional water quality problems, especially if the longer stratification season extends into the rainy season when the highest concentration of particles wash into the lake.

Another concern is the frequency of deep mixing events in the lake. The entire depth of Lake Tahoe mixes on average every four years. “If deep mixing events occur less frequently or disappear altogether, the whole nature of the lake will change,” said Schladow.

Water clarity declining in summer and improving in winter

“In 2011, summer water clarity was the second worst value on record,” the 2012 report states. Researchers think the decline in summer clarity may be related to the impacts of climate change. Lake conditions in recent years are strongly favoring the growth of a tiny diatom –algae cell called Cyclotella. Although it has always been in the lake, its numbers have grown exponentially in the last five years. In Lake Tahoe, scientists are finding that times of maximum Cyclotella concentrations coincide with the lowest water clarity measurements.

Cyclotella diatoms are a very small algae less than 4 microns in size. Photo courtesy of TERC.

While the water clarity continues to decline in summer, winter clarity has been improving for a decade. Additional data would be needed to attribute how much of this is due to improvement in efforts to control urban stormwater runoff and how much is due to changing dynamics in the lake related to climate change.

Staying the course with water quality management efforts

Several years ago, TERC led a team of researchers who conducted a major study of the Lake Tahoe watershed to determine the sources of pollution entering the lake and to establish targets for pollution reduction efforts. Known as the total maximum daily loads, or TMDLs, the targets are established to help managers meet desired goals for water clarity in the lake.

A researcher measures water clarity in Lake Tahoe using a Secchi disk. Photo by Brent Allen, TERC.

Based on that study, tiny particles were considered the main cause of declining water clarity, but with changes occurring in the lake due to warmer water temperatures, researchers are now increasingly concerned about the nutrients entering the lake attached to these particles. “The way to reduce nutrient loads is to reduce the particles coming into the lake,” explained Schladow, “and this is exactly what the TMDL study proposes.”

Recognizing that little can be done at the local or regional level about climate change, Schladow shows no signs of defeat. He believes that by continuing to focus on reducing stressors such as excessive nutrient loading, something can be done to decrease the rate at which the lake loses oxygen. “In this way, we can increase the lake’s resilience so that it can withstand what may come to pass as a result of climate change.”

Making the local-global connection

The local-global connection for lake temperature research is perhaps best exemplified on Lake Tahoe, which was used to calibrate the satellite data in a global assessment of lake temperatures. Buoys deployed for that and other joint studies with NASA’s Jet Propulsion Laboratory (JPL) continue to measure lake temperature every two minutes, 24 hours a day.

“Tahoe is unique because there are very few places where all of this data is recorded on a lake of sufficiently large size that it can be compared with satellite data,” said Simon Hook, a researcher at JPL who led the global assessment.  “It is why places like Lake Tahoe are so important to understanding the trends and ecological consequences.”

Tahoe’s unique characteristics make it an ideal study site. “Because Lake Tahoe is still very clean and relatively pristine, it has a high signal to noise ratio,” explained Schladow. “We can often see things that are happening in other lakes but are just harder to tease out there.”

Hook and Schladow are part of a team of researchers working with the Global Lake Temperature Collaboration to gain a better understanding of the effects of climate change on lakes.

In a previous post on warming lakes, I mentioned that my curiosity about lake temperatures was triggered by a pleasant swim in Lake Michigan this past summer.  Geoff Schladow confessed that he used to joke about the benefits of being able to swim more in a warmer Lake Tahoe. He stopped joking about it because he felt it confused people. “It undervalues all that lakes have to offer,” he said. “Swimming is a trite benefit when considering all that would happen if the lake is that much warmer.”

For more information about the latest research on Lake Tahoe visit: http://terc.ucdavis.edu.

Lisa Borre is a lake conservationist, freelance writer and sailor based in Annapolis, MD. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-wrote a sailing guide called “The Black Sea.” She is a native of the Great Lakes region and served as coordinator of the Lake Champlain Basin Program from 1990 to 1997.

Beaver Island shoreline in northern Lake Michigan. Photo by Lisa Borre.

News reports about warming lake temperatures began to trickle into my world lakes news feed as the summer heated up this year. I read stories about warmer than normal lakes in North America and Europe, including lakes in Kansas, California, and Washington. By the end of July, the Large Lakes Observatory at the University of Minnesota Duluth reported that Lake Superior’s average surface temperature was 8-10°F above average and expected to stay above normal through the remainder of summer.

I had recently returned from a visit with family on Beaver Island in northern Lake Michigan. This was not the first time in recent years that I found the lake surprisingly comfortable for swimming in early July. I was tempted to write it off as an unusually warm summer, which it was. But the news reports comparing lake temperatures to historical records and my own experience at a beach I’ve visited for over 40 years made me wonder what the latest research tells us about the effects of global climate change on lakes. Are lakes warming, and if so, what are the consequences?

Global assessment shows 95% of lakes are warming

In 2010, National Geographic News reported on the results of the first comprehensive global study of lake temperature trends. The study — conducted by researchers at NASA’s Jet Propulsion Laboratory (JPL) in California using satellite data — found that in the last 25 years, the world’s largest lakes have been steadily warming, some by as much as 4°F (2.2°C). In some cases, the trend is twice as fast as the air temperature trend over the same period.

Global trends in seasonal nighttime lake surface temperatures, 1985-2009. Image credit: NASA/JPL-Caltech

Simon J. Hook, one of the scientists who led the JPL study of 150 lakes, became interested in comparing his remote sensing data with actual in-lake measurements, especially on some of the more rapidly changing lakes, to determine what types of ecological changes were occurring. He connected with researchers working on lakes as climate indicators through the Global Lake Ecological Observatory Network (GLEON). Established in 2005, GLEON scientists are creating a network of instrumented buoys to monitor lakes worldwide.

Recognizing the need for a collaborative approach to researching changes in lake temperature and to studying the ecological effects of climate change, they formed the Global Lake Temperature Collaboration (GLTC) in the fall of 2010. The GLTC has since grown to over 50 investigators studying lakes all over the world, including the Great Lakes and Lake Tahoe in North America, Lake Baikal in Russia, and Lake Tanganyika in East Africa. The group held their first meeting in June at the University of Nebraska-Lincoln (UNL) and began pooling data and expertise to better understand global changes in lake temperature.

“Recent studies have revealed significant warming of the world’s lakes,” said workshop organizer John Lenters, a climatologist and lake scientist at UNL and member of GLEON. “The potential impacts of these changes on lake ecosystems make it increasingly important for scientists with access to global lake temperature records to assemble and synthesize relevant data,” he said in a statement before the meeting.

Detailed results of the workshop will be published in the coming weeks and months, but organizers were pleased by the enthusiasm among the workshop participants from 11 countries. They also discovered new data sets for lakes in Europe and elsewhere. “Lake Peipsi, on the border between Estonia and Russia, was one of the lakes in our global study,” said Hook. “It also has a long-term in situ record that we didn’t know existed.” Researchers from Estonia attended the workshop and are now sharing their data as part of the collaborative effort to learn more about warming lake temperatures.

“The number of lakes with both satellite and in situ measurements more than doubled as a result of the workshop,” said Hook. The in-lake measurements support the findings of the remote sensing data: 95% of lakes around the world are warming.

Lakes in North America and northern Europe warming more rapidly

A second global assessment, which used different remote sensing techniques than the JPL study, was published in 2011. The ARCLAKE study used European satellite data over a shorter time period, from 1992 to 2011.

In a special supplement to the Bulletin of the American Meteorological Society published in July 2012, the annual “State of the Climate” report compared the results of the two studies. “Despite differing periods and methods, both ARCLAKE and [the JPL study] are consistent in identifying relatively rapid warming in lakes of both North America and Europe,” the report concluded.

“It’s good that we have two global studies using different methods and data to verify the results,” said Hook. The ARCLAKE researchers are also involved in the GLTC.

Lake water temperatures warming more rapidly than air temperatures

The data from in-lake measurements confirm that water temperatures are warming more rapidly than air temperatures for many lakes around the world.

The fact that lake water is warming more rapidly than air seemed counterintuitive to this lake swimmer. Based on first-hand experience, I know that the warming of lake water in northern climates always lags behind the air in the spring. And in the fall, the lake remains warmer long after the cool autumn breezes begin to blow. When thinking about climate change versus the annual weather cycle, I expected that lake temperatures would warm more slowly than the air. I was surprised to learn that the opposite is true.

Hook explained that lakes integrate changes over time and lake temperatures change more gradually whereas air temperatures change very rapidly. “Lakes are great integrators,” he said. “Measuring lake temperature takes into account all of the variables, such as air temperature, amount of snow melt, the effects of surrounding forest fires, and the amount of biological activity in the water.”

Researchers are also looking at whether changes in other climatic variables may help explain the more rapid warming of lake water.

Lakes are good indicators of climate trends

Just as sailors use their barometers to help predict changes in weather and to understand sometimes fickle winds, climate scientists are finding lakes to be very good indicators of climate change. In addition to being able to integrate changes among many different environmental variables at once, researchers can study these changes relatively easily with the aid of modern technologies. “We can measure lake temperatures from space very accurately and see warming and cooling trends without the rapid daily changes seen with air temperatures,” Hook told me.

Although researchers need 20 years of data to understand climate trends, a growing network of in-lake buoys monitor lakes in near real-time. The buoy data from places like Lake Tahoe, the Great Lakes and GLEON sites can be compared to the satellite data to gain a historical perspective, and eventually will serve as the basis for a long-term record for the lakes themselves.

Our understanding of how lake temperatures are changing around the world has greatly improved in the past few years and will continue to improve through the various collaborative efforts now underway.

This lake sensor buoy on Lake Tahoe helps researchers calibrate satellite data used in global assessments of lake temperature. Photo by John Lenters.

The consequences of warming lakes

Warming lakes are already experiencing water quality problems and increases in toxic algae blooms. Experts predict that the loss of ice cover on some lakes is expected to increase, impacting water quality and possibly lake levels. The potential consequences are enormous when considering how many lakes are affected.

The results of the global assessment of lake temperatures helped researchers working on lakes put their own findings into context. Lake experts are now trying to share their experiences to create a better understanding of the effects of climate change on lakes around the world.

When Simon Hook began studying lakes, he was looking for a better way to understand the effects of climate change. After the results of the JPL study were released, he was pleasantly surprised to find out how interested people were. “People value lakes highly and are concerned about what’s happening to their lake,” he told me. Perhaps this explains some of the enthusiasm for forums such as the GLTC and GLEON. And maybe it will help the groups studying lakes to secure much-needed funding to maintain the satellites, network of buoys and long-term monitoring programs, and to support the unprecedented global collaboration currently underway.

I now realize that it’s too simplistic to look at warming trends in lakes from the standpoint of water temperature alone. The potential ecological consequences are far greater and more complex than just a few degrees of temperature change might imply. In future posts, I’ll explore further how climate change is affecting lakes around the world.

For more information about warming lake temperatures, visit www.laketemperature.org.

Sign at the intersection of the Erie and Champlain canal systems. Photo: Lisa Borre

Last month, the spiny water flea, a tiny shrimp-like organism native to Europe and Asia, was discovered on the “doorstep” of Lake Champlain. Researchers found it in a canal that connects Lake Champlain to the Hudson River, and then a fisherman found it in Lake George, an Adirondack lake located about a half-mile upstream from Lake Champlain.

The findings confirmed everyone’s worst fears: another invasive species made the leap from the Great Lakes and Hudson River watersheds. If it hasn’t already, it won’t be long before it reaches Lake Champlain, which straddles Vermont and New York and is the sixth largest natural lake in the U.S.

The news made me recall the day I stood on the lakeshore with reporters to announce the arrival of zebra mussels in the summer of 1993. I worked as Vermont’s Lake Champlain coordinator in the 1990s, and we had chosen the site where a 13-year-old boy found the first ones while snorkeling near his family’s dock. I felt defeated. It had been five years since they were first discovered in the Great Lakes, and there seemed to be little we could do to keep them out. Once the invasive mollusk becomes established, there’s no way to eradicate it. It was a sad day for the lake.

Fast-forwarding almost 20 years, this most recent news must come as a real blow to those involved with Lake Champlain’s ongoing clean-up and restoration efforts. New York State officials’ announcement about the finding in Lake George on August 1 coincided with the release by the Lake Champlain Basin Program (LCBP) of a four-year status report called State of the Lake 2012. The report identifies the spiny water flea, along with two other species, round goby and Asian clam, as the lake’s most immediate threats, and advises anglers, boaters and other recreational users “to remain diligent in preventing the spread of invasive species.”

The spiny water flea (Bythotrephes longimanus) derives its common name from its thorn-like barbed tail. At less than one-half inch in length, the crustacean earns its bad reputation by feeding on other tiny organisms, including species of Daphnia (other tiny crustaceans) favored by native fish for food. It disrupts the food chain and according to the LCBP website, “can have a dramatic impact on the overall productivity of a fishery.” A recent special issue of the journal Biological Invasions, edited by Norman D. Yan et al., states that spiny water flea “has proven to be a serious threat to pelagic biodiversity in both large and small lakes” in North America.

Spiny water flea found in the Champlain Canal. Photo: SUNY Plattsburgh

Riding in Ballast and Bait Buckets

Many of the invasive plants and animals that plague North American waters arrived in the ballast water of ships. The problem is not unique: the same ships fill their holds with water from the Great Lakes and coastal estuaries, such as the Chesapeake Bay, and return to ports in Europe and Asia. Aquatic species invasions aren’t new phenomena. According to researchers William Ryan and Walter Pitman in their book Noah’s Flood, a species of algae first entered the Black Sea as a stowaway in the bilge water of ancient Greek row galleys. Non-native, nuisance aquatic species pose a threat to lakes, seas, and estuaries all over the world. They have made their way inland to places such as Lake Balaton in Hungary, where zebra mussels arrived in the 1930s through the lake’s connection to the Danube River via a constructed canal.

Residents of the Lake Champlain region appreciate the rich history of the area and are well aware of the important role the lake has played in the history of the United States, due in large part to its strategic position between the St. Lawrence and Hudson Rivers. It is for this reason – its connection to major waterways – that the lake is so vulnerable to the introduction of invasive species like the zebra mussel and spiny water flea.

Experts on Lake Champlain figured it was just a matter of time before the spiny water flea would reach the lake after it was discovered in the Hudson River watershed in 2008. What’s amazing to me is that it was held at bay for so long. Unlike the zebra mussel invasion, the spiny water flea, first discovered in the Great Lakes in 1984, took 28 years to reach the Champlain basin. Although nothing can be done to stop this latest species from establishing itself as part of an ecosystem once it has already invaded, the delay offers a glimmer of hope that a quick response could help delay or prevent it from spreading to other nearby lakes.

Finding the spiny water flea in both the canal and Lake George shines light on the main pathways for spreading this and other non-native plants and animals.  It seems clear that in addition to passing through the canal, the latest invader hitchhiked a ride on a recreational boat, in a fisherman’s bait bucket or attached to fishing gear.

This latest news has triggered renewed debate about how to prevent other species from invading the lake. “I fear that the spiny water flea is just another one of many invasive species threatening Lake Champlain,” the manager of the LCBP, Bill Howland, told me. “It’s cousin, the fishhook water flea, uses the same mode of travel, so it could well be next.” I share his fear.

The round goby, a small bottom-dwelling fish, is moving east in the Erie Canal and south through the St. Lawrence and Richelieu Rivers. Zebra mussel’s cousin, the quagga mussel, is also making its way east through the Erie Canal. The Asian carp probably isn’t far behind.

The LCBP State of the Lake 2012 report states that “waterways in the regions surrounding the Lake Champlain Basin are home to many invasive species that are not found in Lake Champlain.” A telling figure (see below) on page 28 shows 184 invasive species in the Great Lakes, 122 in the Hudson River, and 87 in the St. Lawrence River – all with waterways connecting to Lake Champlain, which currently has 49 invasive species. “There are some vectors we cannot control,” said Howland, “but I’m worried about the remaining 135 species that potentially could be introduced to Lake Champlain.”

All-Out War

Figure 20 on page 28 of the State of the Lake 2012 report showing non-native aquatic species threats to Lake Champlain. Image credit: LCBP

“The spiny water flea is one more lost battle in a long war against invasive species,” said Howland. But ever optimistic, he and his Lake Champlain partners are already laying “battle plans” to prevent future critters from invading the watershed and to slow the spread of ones that are already there. But as Howland is quick to point out, the war analogy ends there. The LCBP has learned from experience to employ a collaborative approach to solving difficult problems such as this. “Our role is to bring the various interests to the table and find solutions,” he reminded me. This is the way it’s done on a lake shared by two states, two countries and hundreds of local jurisdictions.

In addition to the ongoing public education efforts and regulatory programs, one option on the table is creating a physical barrier on the Champlain Canal, one of the main pathways for nuisance species entering the lake. Shortly after zebra mussels arrived in Lake Champlain, researchers conducted a feasibility study for creating an electronic barrier dam in the canal, but the idea never gained much traction because it was not considered cost-effective at the time. A 2005 feasibility study by Lake Champlain Sea Grant concluded that physical or mechanical modification of the canal and/or locks would be “the most effective at stemming the flow of canal-borne invasives.”

In a press release on July 30, the Lake Champlain Basin Program’s Aquatic Invasive Species Rapid Response Task Force called for “immediate action to prevent the spread of spiny water flea into Lake Champlain by slowing the movement of spiny water flea through the canal systems, and development of a long term solution to address the Champlain Canal as a vector for all aquatic invasive species moving in and out of the Lake Champlain Basin.” They also recommended “pursuing a hydrologic barrier on the Champlain Canal that will address the other aquatic invasive species that are threatening to invade Lake Champlain.”

Revisiting the idea of creating a barrier on the canal seems prudent, especially when considering the very real threat that other species pose to the lake. Lake Champlain International (LCI), a nonprofit focused on water quality and fisheries, has already started a petition to disconnect the canal from the lake.

Although this and other issues on Lake Champlain are inherently local in nature, they have global implications. The LCBP partners have become a role model for others tackling similar problems in lake watersheds around the world. The arrival of spiny water flea is a real wake-up call and not-so-gentle reminder of the need to act quickly in order to prevent other species from entering the lake before it’s too late. Like the zebra mussel before, the quagga mussel, round goby and Asian carp will soon be knocking at the door.

Links to more information:

• Global Invasive Species Database
• USDA National Invasive Species Information Center
• ANS Task Force, Stop Aquatic Hitchhikers, Protect Your Waters Campaign
• Spiny Water Flea Fact Sheet and Distribution Map (USGS)

Lisa Borre is an Annapolis-based freelance writer, lake conservationist and sailor. With her husband, she co-founded LakeNet, a world lakes network that was active from 1998 to 2008, and co-authored a cruising guide called The Black Sea based on their sailing voyage around the sea in 2010. Lisa also served as the Vermont Coordinator of the Lake Champlain Basin Program from 1990 to 1997.