Although many of our samples were sent ashore yesterday to be tested at shoreside labs in accordance with Natural Resource Damage Assessment (NRDA) protocol, scientists retain some onboard for their own use. For example, they are using some of the dissolved oxygen samples to run backup tests to ensure our equipment is calibrated correctly. Scientist Kevin Mouyard spent a large part of his morning performing a technique called a Winkler titration on some of the samples. A titration is a technique where you add a chemical that will react with the substance in the sample you want to measure. In this case, Kevin is measuring dissolved oxygen. Kevin added sodium thiosulfate to the sample and set it on a machine that stirred the sample to help it absorb the sodium thiosulfate, and could determine when the titration was complete.
In another lab, Molly Redmond of the University of California Santa Barbara used samples of water taken on a recent CTD cast to grow oil-eating bacteria. She used a syringe to inject methane gas into the samples (which were sealed with rubber lids) so the bacteria would have something to eat and hopefully multiply for future experiments.
Next door, Lindsay Werra and Stephani Shusta, also of UCSB, use a gas chromatograph to test samples for methane. They use a syringe to extract air – into which the methane in the water is released – from the “head” space (the area of air between the surface of the liquid in the sample container and its seal) and then inject it into the chromatograph, which provides a readout of the amount of methane in the sample.