September 5, 2012 Jackie’s work
I first went out with Dr. Jackie Grebmeier in 2002 and this makes my 8th time on a research cruise with her. When I first traveled with Jackie she was at the University of Tennessee, Knoxville, but she is now at the Chesapeake Biological Laboratory (CBL), University of Maryland Center for Environmental Science (UMCES). The web page where you can read about all of Jackie´s work and the work of her husband, Dr. Lee Cooper, is http://arctic.cbl.umces.edu. Jackie´s work involves benthic organisms (those that live on the bottom), and she´s been doing work in the Arctic every year since 1984. RUSALCA is a unique program because of its long-term nature (2004-2012), but this isn´t the first time Jackie has been part of a joint US/Russian research cruise. She first started her international Russian collaboration in 1988 as part of the US-Russia BERPAC program to study the Pacific Ocean and Bering and Chukchi Sea ecosystems. On the RUSALCA'04, '09 cruises and our current cruise, she is particularly interested in reoccupying stations for time-series studies that she has investigated in both Russian and US waters since 1988. Much of Jackie´s work over the years has been in three "hot spots" in the Bering and Chukchi Seas. These are relatively shallow areas where most of the food in the water column goes to the sediments. By studying the organisms living on the bottom, as well as the characteristics of their environment, Jackie hopes to understand the role they play in the cycling of carbon, the element critical for all living things. By studying these same areas repeatedly over the years, Jackie gets a time series that allows her to better understand the forces at work in the water column and the sediments and any changes over time. She looks at carbon supply to the sediments, recycling of carbon within the sediments, and the community structure of the invertebrate macrofauna (large animals) living in or on the sediments.
Early in a full biology station, Jackie collects bottom water from a bottle on the CTD rosette. Jackie needs the water from each station for use in her sediment respiration experiments. While everyone is still collecting water from the CTD, Jackie and our Russian counterparts will start getting mud from the van Veen grab. The van Veen is essentially a large two-sided scoop that goes into the water open and then closes to gather mud when it hits bottom. This cruise stays in relatively shallow water, so it doesn´t take long for the van Veen to go in, reach the bottom, and return to the surface with mud. From the first grab, Jackie takes sub samples of the mud through a small door that opens on the top of the van Veen. Other members of the science party, both Russian and American, also take mud from this first grab. Jackie´s samples are for TOC (total organic carbon), sediment grain size, and for sediment chlorophyll analysis. By analyzing these samples, Jackie will get information about the TOC reaching the sediments, including phytoplankton (tiny plants in the water) and plankton detritus (organic debris formed by decomposition). By analyzing the grain size, she´ll get an indication of the speed of the current as well as the physical environment the animals are living in. We'll then sieve the first grab for Dr. Monica Kedra, Jackie's postdoctoral student who is a part of our team and who is collecting samples for her own work on sipunculids (a type of worm). The next four grabs are for quantitative infaunal population analysis, followed by one more grab for the food web team (see 9/1 journal) and one for a Russian grad student doing her own project. For each of our four quantitative grabs, we dump the mud into sieve boxes with one-millimeter screens on the bottom and use hoses to clear all the mud. We then preserve the organisms that remain. Jackie will take them back with her to the CBL sorting lab, where they will be analyzed to learn what lives in the bottom sediment and how the animals interact with their environment.
Once we have our grabs, Jackie sends down the Haps core, a piece of equipment designed to bring up a core sample of the bottom. Her goal is to get two cores that are approximately 2/3 full of undisturbed mud with overlying seawater. With these two cores in collection chambers, Jackie will do 12 - 24 hour respiration experiments, allowing the organisms to remain in their "natural" environment in order to study total sediment community metabolism. She measures the flux of dissolved oxygen during the experiments as an indicator of carbon supply to the benthos, as well as takes measurements of nutrients and water for carbon dioxide exchange over the course of the experiment. Once the experiments are completed, we´ll sieve the core mud and preserve the organisms. We also collect another core at the site for us to section, can, and freeze. These sectioned sediment cores allow her to determine how long it has taken for phytodetritus (phyto = plant) to reach the sediments and what the longer-term sedimentation rate is for the core sample. They will also be used for radioisotope work by her co-Principal Investigator on this project, Dr. Lee Cooper. Although he´s not on the cruise with us, Lee is also a researcher at CBL/UMCES and he'll measure the levels of radioisotopes in the sediment sections to determine particle deposition rates and down core dating of when material settled to the sediments. During the cruise, Jackie has also taken water samples from the CTD for Lee to determine the ratio of oxygen-18 (18O) to oxygen-16 (16O) in seawater. By comparing the ratio of 18O/16O, Lee can track the fresh water components, which include melted sea ice as well as precipitation. At these latitudes, colder temperatures result in precipitation that is depleted in 18O relative to the freshwater component of sea ice.
Note: Although we were able to get cores at nearly every station in 2009, the weather on this cruise has been such that putting the Haps core in has been impossible. The attached picture was taken on the 2009 RUSALCA cruise. The picture of the van Veen entering the water is also from '09.