19 July, 2004
Although there are a few water stations left, we finished our mud stations just before lunch today after starting them at midnight last night. Even though it was late and we were all tired, it was great to be on deck as the fog lifted and the sun finally came out, staying up for most of the evening. At one point, we had a sunset that lasted for some time before the sun dipped just below the horizon and then re-emerged soon after. It was strange to go from helping Bryan with his mercury sampling (see the journal entry from the 16th) using the strict "clean hands, dirty hands" technique, to the deck where we work with Jackie's sampling and get wet and covered in mud! Although it's somewhat repetitive work, and it's often cold on deck, the mud seems to have a certain allure. Many of the crew have come to check out our samples, and one even joined us today to help out at a complete station. Check out the photo of Vivien Summers, the ship's medical officer sieving a grab!
Jackie's work involves benthic organisms (those that live on the bottom), and she has been studying this same area annually since 1984. It's important to understand what organisms live on the bottom and the characteristics of their environment in order to see what role they play in the cycling of carbon, the element that is so critical for all living things. If you check the cruise map in the journal from the 13th, you'll see three areas circled. These are "hot spots" where the water is shallow and most of the food in the water column goes to the sediments. By studying the same three areas over a number of years, Jackie gets a time series to better understand the ecological forces at work in the water column and the sediments. For example, she looks at the carbon supply to the sediments, recycling of carbon in the sediments, and the community structure of the invertebrate macrofauna (large animals without backbones). These three areas are also important because they are home to important top predators such as the spectacled eider (a threatened population of diving sea ducks), walruses and gray whales.
Over twenty years, Jackie has seen a decline in the population of the dominant invertebrate fauna in these three areas. The changes seem related to changes in water temperature, current flow and carbon supply. For example, the population of amphipods (a small, pink shrimp-like animal) has declined in the Chirikov Basin and the gray whales are moving north in search of food. This area is critical because all the major water masses of the Bering Sea come together through the Bering Strait and move into the Chukchi Sea. When Jackie leaves the Laurier, she'll return to the USCGC Healy where she will continue work on the Shelf Basin Interactions project which picks up the study further north. All in all, she will have been out to sea for three months by the time she leaves the Healy in late August.
In order to do her benthic studies, Jackie uses the van Veen grab and the Haps core. She gets five grabs and three cores from each station. From these she takes sub samples to analyze for chlorophyll, HPLC see journal for the 15th), carbon-13, cesium-137, beryllium-7, TOC (total organic carbon) and TON (total organic nitrogen). Analysis of these samples yields information about the phytoplankton and how long it has taken to reach the sediments, the forms of carbon and how much of it arrives at the sediment surface from the processes taking place in the overlying water column, and the source of the organic material in the mud. In addition, she looks at the grain size of the sediment to get an indication of what organisms might live there.
With her cores, Jackie will do 12 - 24 hour respiration experiments, allowing the organisms to remain in their "natural" environment so she can study total community metabolism. She will sieve these cores at the end and preserve the specimens.
Ari and Rebecca take 1 or 2 cm. sections vertically of the other cores, placing the mud into cans and freezing it to bring back to the University of Tennessee for analysis.
I promised you some photos of the van Veen work including getting the mud and sieving it (check the journal from July 15), and I've included those today along with some of Jackie's work. The picture of the sieved mud grab shows lots of mollusks (clams and a few snails) and worms, but we have also found a few small sea cucumbers, lots of pink brittle stars, a few crabs, and an occasional sea anemone. All the sieved samples are preserved and returned to the University of Tennessee for analysis. I'm not sure who to thank for some of the pictures since I took them from the file from the ship.
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