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13 March, 2000

Today has been foggy but much calmer. The temperature is still at 3 degrees. The sampling work is going much smoother without the waves. Much of the analysis of the samples will take place back at the scientists universities and laboratories. There are scientists and graduate students on this cruse from: University of Hawaii, N.C.

State University, Rutgers, Texas A&M, and the Natural History Museum in London, England.

Dr. Hilary Hartnett is working with sulfur fixing bacteria from the sediments. Her BS in Chemistry from Vassar and her Masters and PhD. in Oceanography from University of Washington have prepared her for this work. She first takes a subcore from the larger sediment cores brought up from the ocean bottom with the megacorer. The sediments contain bacteria which use sulfur instead of oxygen to metabolize nutrients. If the amount of sulfur used by these bacteria is

measured this data can then be used to help determine how fast the nutrients in the sediments are being metabolized. The problem is

that there is too much sulfur in the ocean water to accurately detect rates of change in the amounts. Dr. Hartnett uses a radioactive isotope of sulfur which can be traced to solve this problem. She injects the measured amount radioactive sulfur into the sediment sample each centimeter and stores the sample at ocean bottom temperatures (about 1.5 degrees Celsius). The rate of change in the known amount of radioactive sulfur can now be measured. This is done in a laboratory in Germany. The data is used to determine the nutrient uptake by these bacteria which is important in answering the questions of how long the nutrients from the summer increase in organisms and activity remain available for metabolism throughout the rest of the year, one of the questions of this research.

Dr. Hartnett does all of her work on deck in a small container lab. Even though the level of radiation is low, she follows the safety protocol for working with a radioactive isotope.

Dr. Hartnett injecting radioactive sulfur into a sediment subcore.

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