Stable Isotope Ecology

Once the filter devices were assembled, we brought them out to the back deck and connected each one to a larger apparatus housing the pumps and batteries. The pumps will move ocean water through the filters at a steady rate, and can track the exact volume of water going through the filters.

Then, each apparatus was attached to the same rope and lowered into the ocean at varying depths 25-50 meters apart. This way, each device could gather data at different depths in the ocean. The pumps stayed submerged for four hours to gather particles (nap time!). It was important that the boat wasn't moving the whole time and that the waves were relatively calm while the devices were underwater so that the rope would stay as close to vertical as possible and keep the depths of the pumps as consistent at possible.

After the four hours, the process to submerge the pumps was basically reversed, bringing each one up one by one and detaching them from the rope. Then, the filter devices were brought into the lab.

Back in the lab, we had to disassemble each layer of the filter device to expose the debris covered filters. Then, for each Nitex filter, we carefully sprayed the particles off with filtered sea water, and funneled the particles onto a smaller GF/F filter. These pieces were then put in a small plastic bag for storage. With the GF/F filters, we punched a smaller circle out of the middle, and put the small punched out circle and the rest of the GF/F filter in separate bags. Later, the small filters will be analyzed via compound-specific amino acid stable isotope analysis, and the larger GF/F filters will be analyzed via bulk analysis. With this data, we can calculate the isotope distribution at these varying depths, which can be used to analyze the trophic level distributions.