Plankton Communities and Marine Snow in the Gulf of Mexico as Estimated by the Video Plankton Recorder (VPR) During Spring 2011

Abstract

Plankton are an integral component to marine ecosystems globally, as they are the foundation of the marine food web. The offshore Gulf of Mexico (GoM) is an area which supports large fisheries, as well as a growing offshore oil and gas industry. The event of the Deepwater Horizon oil spill disaster accentuated the historical lack of data characterizing plankton communities in these waters. Overall, the majority of plankton research in the GoM has concentrated on the shelf waters, focusing primarily on larval fish and eggs, leaving the offshore plankton communities understudied. These prior studies employed nets as the primary method for sample collection, thus they are inherently coarse in their spatial resolution. Extrusion through the meshes of nets causes fragile plankton, and delicate particles (marine snow) to be under sampled. Using the Digital Autonomous Video Plankton Recorder (DAVPR), spatially detailed data on major plankton taxa, and marine snow, as well as coincident environmental data (temperature, salinity, density, dissolved oxygen, and chlorophyll), were collected at nine stations in the deepwater (>300m) GoM during spring (April – May) 2011. Remotely sensed satellite data were acquired to visualize the regional distribution of sea surface properties for elevation, temperature, and chlorophyll concentration. Plankton and marine snow distributions in the GoM offshore waters were correlated to the distribution of environmental parameters in both the vertical and horizontal. Two prominent hydrographic features that were present during spring 2011 study had the most substantial impact on plankton communities. A single station (S5), located furthest to the north was influenced by low-salinity, nutrient rich, shelf water at its surface to ~25m depth, which greatly enhanced the biological activity at this site. The southeastern stations (S7, S8, and S9) were located along the frontal boundary of the Loop Current. In these sites where the LC brought higher salinity, denser, oligotrophic water to the upper 200m of the water column, the cyanobacterium Trichodesmium was strongly associated. The stations located outside the hydrographically unique stations (S5, S7, S8, and S9) had plankton communities that were largely similar. Plankton communities were characterized as being specific to stations sharing a similar environmental structure.