A Molecular Survey of Diatom Communities in the Subpolar and Subtropical North Pacific

Because diatoms and other eukaryotic phytoplankton facilitate biogeochemical cycling and carbon export, their biodiversity and community structure can profoundly impact marine ecosystem processes. Although diatom populations differ across oceanographic regions, few studies have assessed how communities are affected by environmental variables. Here, we use 18S rRNA gene sequences to assess biodiversity and diatom community structure in the Northeast Pacific along a cruise track passing through coastal, subpolar, transition zone, and subtropical oceanographic regions. We are focusing on diatoms in the 1.6 μm–53 μm size fraction from surface and chlorophyll maximum depths collected from ten sampling sites. This study will enable us to determine how diatom communities differ in each region, which species co-occur, how nutrient concentration, temperature, and salinity affect community composition, and which of these variables are most influential. Preliminary results show high species richness at coastal stations, decreasing in the open ocean.