27 July, 2002
Due to the great depth (2000 meters) at this station, we only did the Haps core sampling for the mud at the bottom. The five van Veen grabs would take up too much ďwire timeĒ (the time it takes to send the equipment down and back). The multi-Haps core sampler should pull up four cores at a time and, by sending it down twice, Jackie will have more than enough samples. However, it is not unusual to run into problems, especially at these depths, both due to equipment and changing drift conditions. Today we had to send the corer down three times in order to get the samples we needed. Thanks to Steve Roberts, the JOSS (Joint Office of Science Support) data management person on board, I have a record of the sampling process. Be sure to check it out in the series of pictures below.
Keep in mind as you look at the pictures that Jackie Grebmeierís interest is the benthic organisms. Itís important to understand what lives at the bottom and the characteristics of their environment (the sediments) in order to see what part they play in the overall scheme of carbon cycling. When the cores come up, sub samples of the sediments from one of them are taken for a variety of tests. A chlorophyll test gives an indication of the phytoplankton present in the sediment. Remember that phyto means plant and phytoplankton contain chlorophyll, a green pigment found in all plants. Another sample is collected for HPLC analysis. This is high performance liquid chromatography, a fancy name for a process that separates out the phytoplankton by the pigments (colors) they contain. Another sub sample yields TOC (total organic carbon) and TON (total organic nitrogen). The results can provide an indication of the source of the organic material in the mud, a ratio of marine (salt water) to terrestrial (terra = land) organisms. Carbon-13, an isotope of carbon, will be analyzed from the same sub-sample and will provide similar information. Lastly, we preserve the samples for analysis for a series of radio-isotopes such as beryllium-7, lead- 210, cesium-137, plutonium, and radium. These are called tracers because they tell us what forms of carbon and how much arrives at the sediment surface from overlying water column processes.
Once all the cores are on deck and the sub-samples are removed, Jackie chooses two cores for her 12-24 hour respiration experiments. (Check out the journal photos for July 22.) When she is finishes with those, they are sieved to remove all mud and to preserve the organisms left behind. We then take one of the other cores collected to cut into sections to be canned and brought back to the University of Tennessee for further analysis. Thatís the time when we get to come inside and actually work with the mud. When itís not full of byssal threads from mussels in the core, itís an easy job. We take off one centimeter (a little less than Ĺ inch) slices at a time for the first four sections. After that we remove two centimeter slices until the core is finished. Because we are near the end of the sampling at each station, we are often working into the early morning hours or even through the night. In case you think that is difficult, check out the last picture to see what our surroundings look like while we are on deck!
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