Question ?  From: Gustavus School, Gustavus, AK

We were reading all about the sediment sample gathering technique and we were wondering what type of data do you get from the sediment and how is it incorporated in the overall study.

Greetings from Antarctica! My name is Kathy Conlan. I am a marine biologist at the Canadian Museum of Nature and am working with Stacy Kim on the impact of sewage pollution on the marine life that lives on the sea floor near McMurdo Station. I hope I can answer your question about our sediment sample gathering technique.

Here are two pictures so you can see what I mean. The first is what the community looks like where it’s clean and the second is what it looks like around the sewage outfall. These pictures are in our latest publication on our studies, published in Marine Pollution Bulletin 49: 43-60 (2004).

We focus our sampling on these little animals (rather than big things like seals and penguins) because there are many different species living on the seafloor and because most of these animals can’t escape. If these animals are suddenly hit by pollution, they can’t swim away as penguins or seals could. As well, if the pollution is really bad, then just about all the different kinds of animals (snails, clams, crustaceans, and worms) will be killed by it, so we will know that the impact is really bad. If other kinds of animals that do not normally live there like the pollution, however, then they will move in to take their place. They move in, either by swimming or crawling as adults, or more often by releasing their youngsters from afar. These youngsters, which are often larvae, are good at swimming and finding new places to settle. What we are finding living in the sediment near the sewage outfall is an abundance of sewage-loving worms that LOVE all that messy stuff that McMurdo is dumping out. They think it’s great food and don’t mind that there is not much oxygen around anymore. So they multiply like crazy and become super abundant. Farther away from the sewage outfall, where there is less stuff for these sewage worms to eat, the community will change. We will find a few of the sewage worms living there along with a few of the clean animals, and also some new ones that like a bit of sewage but not too much. This is the community that tells us that the sewage is still having an effect but not too much. So now that the staff at McMurdo Station has started treating their sewage, which means less food getting dumped onto the seabed for the sewage worms to eat, we hope that the clean animals will start moving back. Maybe they can live nearer the outfall than they did a couple of years ago when raw sewage was still being dumped. one of our clean sites far away from McMurdo's sewage outfall Two years ago, Stacy set up a whole bunch of dishes filled with clean sediment mixed with peas, corn and beans to simulate sewage food and we put these out far away from the sewage outfall where it was really clean. In other dishes she had only clean sediment. Now we are picking those dishes up off the seafloor and looking to see what animals colonized these dishes over the past two years. We found that at Turtle Rock and Cinder Cones, which are near the open ocean, those sewage worms have been finding our enriched dishes. That means that these sewage worms must be able to live naturally here and there, perhaps where seals and penguins are around, and if they find a good source of food (such as our dishes) then they will multiply like crazy. However, at New Harbor and Cape Bernacchi, which are far away from open ocean, they are not finding our dishes. We think this is because New Harbor and Cape Bernacchi are so clean all the time that there is not enough food to keep even a few sewage worms alive. There are no seal or penguin colonies here and the water supply comes from under the huge Ross Ice Shelf where it is dark, rather than from the open ocean where there is a good food supply from sunlight. McMurdo's sewage outfall before sewage treatment was added in 2003 We don’t know whether the clean animals have moved back to the outfall and the sewage worms disappeared this year as we have not had the time to examine the animals under a microscope and identify them (as you can see in the picture, there are a lot of different species to learn to recognize). The staff at McMurdo has to support so many other scientists that they want us to stay for as short a time as possible. So all we can do while in Antarctica is it to drill dive holes through the ice at all our different sampling sites, take our cores of sediment and relocate our experimental dishes, sieve the animals out of the sediment, preserve them, and pack them up to ship home. We will do the identifying and look for changes in the communities once back home. There is a meeting this July in Brazil where all the Antarctic biologists from around the world will get together and present their results. The meeting is held every three years. We will have to hurry and work to identify our animals once home again so we can see what changes have been happening once McMurdo started sewage treatment in 2003. We want to present what we find at this meeting. That’s part of the work of being a scientist. Going to Antarctica and diving and enjoying all this beautiful scenery is wonderful (though it’s also hard work!). But the excitement of discovery actually comes later in the lab back home. Then we get to tell our results to everyone else at meetings and then publish them in journals. That is when our peers evaluate whether we did the sampling properly so that our conclusions are valid. Then we discuss the results with our colleagues, set more hypotheses, and maybe apply to return to Antarctica again to answer more questions. It is a stimulating and exciting life being a scientist, especially in beautiful Antarctica!