July 17, 2006 Options

[Betty_Carvellas]

July 17, 2006

I can tell I'm tired. I had just started to write this journal when I went back to check my journal of July 14 where I started out with "It's probably time that I told you what happens at a mud station." In that entry I told you all about the water collected from the CTD and about Rebecca and Lee's work. But, I never got you out on deck for the real mud part. So, here goes. You have loads of pictures from yesterday's journal and a few more today for reference.

So - here's a review of All that happens at a mud station. First there's a CTD cast off the port side. As soon as that's done, the crew moves to the well deck up front, and we start our mud work. We need to get 5 van Veen grabs and 3 good Haps cores at each station. While that should mean 8 times up and down with the winch, it often means more when it's difficult to get good cores due to mud conditions or if the van Veen doesn't close. If you check out the pictures from yesterday's journal, you can follow along with the van Veen work. The first time the van Veen comes out of the water, someone will take samples off the top for TOC (total organic carbon), sediment chlorophyll analysis and HPLC (high performance liquid chromatography, used to analyze the pigments in the phytoplankton.) We also fill a Marinelli beaker with mud which Lee will bring back to the University of Tennessee to analyze for Beryllium 7 and Cesium-137 to determine sedimentation rate. 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.

For the next 4 grabs, we dump the mud into sieve boxes where we clear all the mud with hoses and preserve the organisms left behind to get an idea of what lives at the bottom and how it interacts with its environment. A typical grab might include lots of different worms and clams, but we've also found snails, starfish, sea anemones, shrimp, amphipods (small, shrimp-like creatures that are food for grey whales), and even, at one particular station, lots of sand dollars.

When the van Veen grabs are done, Jackie will send down the Haps core to get a core sample of the bottom. When she gets 2 good undisturbed cores, with a layer of sea water on the top, she'll take those for her respiration experiments. By allowing the organisms to remain in their "natural' environment, Jackie can study total community metabolism. Rebecca will take the remaining core into the van on deck where we work, and she'll "cut" the core, taking one centimeter sections of the core for the first 4 centimeters and packing, canning, and freezing the mud from each section.


Lee is getting ready in the van for another station. The van is set up on deck, and it holds much of our mud equipment and provides a place to work to cut the cores and preserve the mud animals from the grabs.


Jackie is getting ready to guide the Haps core over and into the water. You can see the core barrel at the bottom.


Jackie looks very happy because she's just gotten a good core for her respiration experiments. In the background you can see the green van where we process the mud.

Jackie has been sampling in this area for more than 20 years, and this is her second cruise here this year. She completed a 30 day cruise on board the USCGC Healy just before returning for this cruise 3 weeks later. Jackie studies benthic organisms (those that live on the bottom) and the characteristics of their environment in order to understand the cycling of carbon, the element found in all living things. If you look at our cruise map, you'll see 3 clusters of stations. By sampling in these same 3 "hot spots," where the water is shallow and most of the food in the water column goes to the sediments, Jackie has a better understanding of the ecological forces at work in the water column and the sediments. She looks at 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 diving sea duck), walruses, and grey whales that feed on animals in the sediments.

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.


Jackie is only on deck gathering mud part of the time. She also spends a great deal of time in the ship's lab.