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> July 19 - 2005
Betty_Carvellas
post Jul 20 2005, 09:23 PM
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July 19, 2005

In 2002, when I worked with Dr. Jackie Grebmeier on board the USCGC Healy, I never dreamed I'd have the opportunity to return to the Arctic with her, and here I am on my second science cruise on the Sir Wilfrid Laurier. Many of my friends and relatives find it difficult to believe that I would want to use a part of my summer vacation to leave Vermont and go north to work with mud on a ship in the Arctic. They have no idea how exciting it is to be here and to be a part of the on-going research in this critical part of the world. In terms of global climate change, many see the Arctic as the canary in the coal mine. The climate is changing here more rapidly than anywhere on earth, and scientists are working hard to understand exactly what is happening.

Jackie's research involves benthic organisms (those that live at the bottom), and it takes us out on deck for each of the mud sampling stations. As I've noted before, we take five van Veen grabs and three HAPS core samples at each station. If you check my journal from the 15th, you can read about the different sub samples that we take from each grab and core, and see some pictures of the van Veen work. By analyzing the sub samples, Jackie gets 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 type of organisms in the mud. Analysis of the sediment grain size gives an indication of current speed as well as the physical environment the animals live in. Jackie also takes two undisturbed cores from each station for 12 - 15 hour respiration experiments. By allowing the organisms to remain in their "natural' environment, she can study total community metabolism. I've added pictures of the HAPS work today. I was waiting for some sun to take the pictures, but that never happened; you'll get to see the weather as it's been for nearly the entire trip.

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It's important to understand what lives at the ocean bottom and the characteristics of their environment in order to understand the role they play in cycling carbon, the element that is so critical for all living things. In my journaly of July 10, I posted a picture of our cruise map. The circled areas are "hot spots" where the water is shallow and most of the food in the water column gets to the sediments. By studying these same areas for a number of years, Jackie gets a time series to better understand the ecological forces at work in the water column and the sediments. She looks at carbon supply to the sediments, recycling of the carbon in the sediments, and the community structure of the larger invertebrates (animals without backbones). It's critical to know what's going on in these hot spot areas, because they are home to important top predators such as the spectacled eider (a threatened population of diving sea ducks), walruses and gray whales that feed on animals in the sediments. It's interesting that we saw so many gray whales last night, because we're past the area where we found amphipods (their favored food source) in the mud grabs. That's another question for possible investigation!

Over years of sampling these same areas, Jackie has noticed a decline in the populations of the dominant invertebrate species. The declines seem related to changes in water temperature, current flow and carbon supply. One example that we've noticed is the difference in the abundance of different groups of clams. When we're sampling in different areas, it's always fun to sieve the mud and see what animals we find. Although we find things like brittle stars (a small, pink starfish), tube worms, snails, the amphipods I showed you, and an occasional sea anemone, the clams are a constant. Since they are a food source for both walruses and the spectacled eider, the clams are a critical part of the ecosystem. The spectacled eider likes to feed on the tellinid clam, a soft shelled clam with lots of meat and therefore calories. With the changing environment, the numbers of tellinid have declined and the population of the nuculanid clams has increased. Nuculanid clams have tougher shells and less meat, making it difficult for the eiders to find sufficient food. Although I have not seen the changes over the years, I do know that, in the last two years, I've seen lots of nuculanid clams in the grabs and not as many tellinid clams. Jackie tells me that this is the reverse of what she saw in the 1980's.

"insert picture - sieve box critters.jpg"

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