Ice diving for Capetella

Thanks to the students of Nespelem Middle School for an excellent Skype conversation this morning. I was really impressed by the depth of some of the questions asked! Thanks also to teacher Sheri Edwards for facilitating and writing a nice article about it here.

It seems like Shelly and I have been doing nothing but filter water for the last several days, but the end is in sight. I think we’ll finish off the last of our samples this evening, then it will be time to turn our attention to getting some new material. It’s difficult to know when our next opportunity to get on the sea ice will be. On Monday the main science season starts. Three planes each week will bring new scientists and staff for the station. There will be a LOT more people around and many more demands on the safety personnel. For the last four weeks there has been only one other group doing science on the sea ice, a team led by Prof. Adam Marsh at the University of Delaware. This group studies the physiology of polychaete worms that live in the sediment of McMurdo Sound. I’m a tad jealous of them because they collect their samples by diving underneath the sea ice, something that I’ve wanted to do ever since I learned it was possible (probably by watching Jaque Cousteau as a kid).

Every Sunday evening one of the science groups gives a public talk in the dining hall on their work. Last week Adam and his team presented, this Sunday it’s our turn. I learned some fascinating things about some of the marine ecology of McMurdo Sound. The benthic, or seafloor life in the Sound is very dense, looking much like a tropical coral reef.  Except in place of hard corals McMurdo Sound has large, delicate sponges. The deeper you go the bigger and denser life gets. This is a result of icebergs continually scouring the shallows, removing everything before it has a chance to get large.

The polychaete worms Marsh’s group studies like to live in places other organisms won’t, such as the sewage outflow site for McMurdo Station. Until recently McMurdo didn’t treat its sewage, and the sediments at the old outflow are particularly rich in organics. Bacteria are quick to colonize such spots and consume the organic material so quickly that all the oxygen is used up. The worms can tolerate lower levels of oxygen than most animals, and also like the high concentration of organics. They burrow through it leaving tunnels that allow new oxygen-rich water to enter. This allows other organisms to follow along and further degrade the organic material.

The group is particular interested in a genus of polychaete worms called Capetella. This genus, in addition to being especially tolerant to low oxygen conditions, is highly resistant to many toxins found in marine sediments. In the old days everything from McMurdo Station was disposed of by simply dropping it into the Sound. As a result some places in the Sound are highly contaminated with heavy metals, PCBs, and other chemicals. Bacteria can degrade many of these materials over time, but without oxygen they perform this service very slowly. Microbial degradation is likely much enhanced by actively burrowing Capetella.

Joining Adam in McMurdo are fellow benthic ecologist Stacy, graduate students Stephanie and Annemarie, and middle school teacher Mike. Mike is in Antarctica through the National Science Foundation’s Polartrec program which pairs teachers with scientists in the field. Mike dives with the team and shares the experience with his and other classrooms via a blog (with lots of great photos). Check it out if you’re curious about what’s it’s like to dive under the ice in Antarctica!