National Geographic
Menu

Alaska Coral 2013: Back to the Lab!

NG Grantee Rhian Waller has been studying the deep-sea corals found in the shallows of fjords in Alaska, and investigating what they can tell us about the rest of the ocean as well.

 

The expedition is over. It’s back to the laboratory at the University of Maine for both myself and the samples we collected on this cruise. It is time to look back on our field program and realize just how well it went – we had great weather, we had great diving, and we had a great crew – can’t really get better than that.

Sailing out of Tracy Arm, through Holkham Bay as the sun sets. Photo by Rhian Waller.

 

And now to the important part – the samples, the results, and soon, the publications. The focus of this project has been on examining the reproduction and development of Red Tree Corals in Tracy Arm fjord. This is a species that usually lives in a few hundred meters of water in the North Pacific, yet here in the Southeastern fjords of Alaska, we can swim amongst it at just ten meters’ depth. Though exploring why this is is beyond the scope of this particular project, we are hoping to use this phenomenon to tell us more about the deep-sea populations of this coral, where samples are much more sparse and very expensive to collect. This population in Tracy Arm is like a window into the deep-sea, where we can conduct experiments by SCUBA (much easier with your own two hands, than with submersibles or remotely operated vehicles) and revisit the site many times (seven times over two years in this case).

 

Measuring each colony we tagged and sampled is an important part of the project. Here Rhian Waller holds up a meter stick underwater while video of the colony is taken. Photo by Bob Stone.

 

So why are we interested in reproduction? Well, reproduction is a fundamental process that every single species on the planet needs to undergo to maintain populations. How, when, and how much a species reproduces can tell us (amongst other things) how healthy the population is, whether there is a time of year the species should be protected because it’s reproducing, and what are the chances of recolonization after a detrimental effect. These Red Tree Corals form important habitat for many species of invertebrates and fish, they provide protection from predators (lots of places to hide), food sources (through the other animals that live there) and sometimes even a place to lay eggs or raise young. In Alaska alone this species has been found to harbor over a dozen species of rockfish and many species of juvenile crab, making it an important part of the ecosystem. These corals are frequently impacted by fishing gear, and are under threat from changes in our oceans’ chemistry (see this interesting article from the Marine Conservation Institute), and currently we know very little about how these species survive in our oceans or where they live, let alone how to protect and preserve them.

 

Eggs (peach colored) and sperm (opaque) of the Red Tree coral extracted while onboard the research vessel. Photo by Rhian Waller.

 

To study reproduction my laboratory uses microscopy. We take pieces of coral tissue and embed them in wax or plastic and then thin-slice them to just a few microns. We then mount these tiny slices on slides, stain them a variety of colors, and take a look under the microscope to see what we can see. Using these techniques we can see how eggs and sperm are formed, how they grow and what time of year they are produced – all vital information in understanding how these Red Tree corals thrive in the fjords!

 

Sections through the corals tell us a lot of information on how they reproduce. This section is just 5 microns thick, shows a male coral, and is magnified 40 times! Photo by Rhian Waller.

 

Using this information from seven trips to the same site, we’ll build up a time series – a look through the past two years – to see how the corals are reproducing, and whether they are healthy. This is important information alone, but on top of this, when we get samples from the deep ocean, I’ll be able to compare them to these shallow fjords and look for differences, so this research goes farther than just the fjords of southeastern Alaska.

 

The last look at Tracy Arm fjord. I hope one day I'll be back to check on our corals and see how they're doing. Photo by Rhian Waller.

 

Thanks for joining us on our expedition, be sure to tune into our next cold-water coral expedition!

 

See Additional Posts

Alaska Corals 2013 – Heading into Stephens Passage

Alaska Corals 2013 – Days 1-3

Alaska Corals 2013 – Snow, Ice, Corals and Earthquakes!