We are studying the oceanography of the Texas coast, focusing specifically on the distribution of phytoplankton and nutrients in the water column. High nutrients often set the stage for growth of phytoplankton. One particular species that we are interested in is the toxic phytoplankton called Karenia brevis. These algae could be identified in samples taken at key water depths in the water column close to shore or in the middle of the gulf.
At each station, we began sampling water at various depths by dropping an instrument known as a CTD (which measures Conductivity, Temperature, Depth) through the water column. This data is then beamed to us in real time and helps to determine where we collect water samples at using specialized canisters called Niskin bottles. Once the CTD and Niskins are recovered, we draw water from each Niskin and take it to the ship’s wet lab where we process it for a variety of measurements.
For this particular project, samples are processed for nutrients, chlorophyll a, and plankton community composition and relative abundance. But before we can process any samples, we have to be extra careful to rinse all of our bottles with dilute acid and multiple squirts of ultrapure de-ionized (DI) water to ensure cleanliness. We also have to wear latex gloves at all times to prevent contaminating our samples with chemicals that are on our fingers. To process our samples, we filter the seawater through glass microfiber filters using a vacuum filtration apparatus. The filters are stored frozen for return to our shore based lab, as is the water that passes through the filter. We also preserve samples to look at the types and abundance of phytoplankton with a microscope.
Our careful handling of the samples produce data about the phytoplankton community composition and genus/species abundances, nutrient distributions, and chlorophyll a levels, to help build a better understanding of basic oceanographic conditions as well as the ecology of phytoplankton and harmful algal blooms in the western Gulf of Mexico.
-Written by Kelsey Fisher and Lynn Prince, Edited by Dr. Michael Wetz for Schmidt Ocean Institute
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