Diatom Community Composition Shifts in the Nitrogen-limited Mid-Atlantic Bight

Diatoms are unicellular, photosynthetic eukaryotes with high sensitivities to nutrient availability, often leading to rapid shifts in community composition, making diatoms strong bioindicators for environmental change. The Mid-Atlantic Bight (MAB), located off the eastern U.S., is an ecosystem predominantly limited by nitrogen and is home to a complex distribution of nutrients due to coastal waters interacting with the Gulf Stream. In the summer, waters are strongly stratified and phytoplankton communities are dominated by diatoms. Rivers and estuaries in this region can deliver nitrogen pulses, which can lead to community shifts in response to nutrient availability. Previous studies have produced overall phytoplankton composition for this region, naming the top few diatoms present, though have not provided an in-depth species-level diatom community composition analysis for the MAB. We completed a comprehensive surface water diatom species level assemblage analysis along the MAB to help elucidate the coastal-driven effects on the ecosystem as a function of distance from the coast. In order to obtain the species-level resolution, high-throughput sequencing techniques were used on the V4 region of the 18S rDNA marker gene. Quantitative PCR was also performed to acquire a more accurate assessment of the quantity of diatoms present in each sample. The community compositions, when analyzed spatially, highlight the locally adapted, coastal water community being dominated by Leptocylindrus, Cylindrotheca, and Rhizosolenia. Offshore Gulf Stream waters were dominated by Fragilariopsis and Pseudo-nitzschia.https://digitalcommons.odu.edu/sciences_achievement/1000/thumbnail.jp