Carbon export following the North Atlantic spring bloom is driven by biological and physical processes. Plankton-derived carbon can be exported from the surface through sinking of cells, aggregates, or fecal pellets. Alternatively, subduction occurring at eddy perimeters transports particulate carbon to depth by physical advection. As part of the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) North Atlantic field campaign, a coordinated biological, chemical, and physical sampling event took place across the edge of a mesoscale eddy to examine the contribution of eddy subduction to carbon export. During this event, we characterized phytoplankton community composition at varying depths and positions across the eddy front. High throughput sequencing of the eukaryotic 18S rDNA V4 region and a diatom-targeted 18S rDNA region were used to delineate both phytoplankton and diatom community composition in the context of physical water mass properties. Phytoplankton and diatom diversity increased with depth to around 200 m. The highest phytoplankton diversity occurred within a water mass physically characterized as subducted chlorophyll-a. The community composition in this water mass was unique, driven by a higher proportion of sequencing reads from the two diatom genera Chaetoceros and Bacteriastrum. Ongoing integration of the biological and physical datasets will help to reveal whether these taxa were transported via sinking or subduction from the surface, providing a better understanding of carbon export processes in the North Atlantic.

Primary Presenter: Katherine Roche, University of Rhode Island (kmroche@uri.edu)

Authors:

Katherine Roche, University of Rhode Island, Graduate School of Oceanography  (kmroche@uri.edu)

Leah Johnson, Applied Physics Laboratory, University of Washington  (leahjohn@uw.edu)

Zachary Erickson, Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration  (zachary.k.erickson@noaa.gov)

Sarah Lerch, Institute of Marine Research, Flodevigen Research Station, Norway  (sarah.lerch@hi.no)

Mark Brzezinski, Marine Science Institute, University of California Santa Barbara  (markbrzezinski@ucsb.edu)

Bethany Jenkins, University of Rhode Island, Graduate School of Oceanography, College of Environmental and Life Sciences  (bdjenkins@uri.edu)