Biogeography of Phytoplankton Community Structure in the Northern Gulf of Mexico

The northern Gulf of Mexico is a dynamic and diverse ecosystem that is driven by a complex circulation pattern. Previously we have shown that the abundant natural hydrocarbon seeps along the continental slope enhance surface phytoplankton chlorophyll concentrations locally. The Mississippi River plume coming from the north is rich in nutrients, delivering 90% of the total nitrogen and 87% of the total phosphorus load to the basin. In contrast, the loop current to the south is depauperate in nutrients and sheds mesoscale eddies with attendant smaller scale features. These large and small scale forcings result in high spatial and temporal variability in the phytoplankton community structure. We used an Aquatic Laser Fluorescence Analyzer plumbed to the ship’s flow through system and High Performance Liquid Chromatography measurements of water samples from various depths to measure phytoplankton pigment concentration and composition in the northern Gulf of Mexico. We will present the results of this study in the context of natural hydrocarbon seeps and nutrients and discuss the biogeography of phytoplankton in the northern Gulf of Mexico.