Impacts of microzooplankton grazing on size-fractionated transparent exopolymer particle (TEP) production in the California Current

Transparent exopolymer particles (TEP) are gel-like polysaccharides ubiquitous in oceanic habitats. These carbon-rich sticky particles, produced by phytoplankton are crucial for marine aggregate formation, providing an important mechanism by which carbon and other material are transported to depth. In addition, as major consumers of phytoplankton, microzooplankton have the potential to alter TEP production. Consumption of TEP and/or affecting TEP production by microzooplankton could alter the size distribution of aggregates, subsequently affecting sinking rates, therefore impacting carbon flux. Over a 28-day expedition in the California Current during May-June 2024, 24 h size-fractionated TEP production and dilution experiments were performed concurrently every other day to estimate rates of size-fractionated TEP production (<20 µm, <200 µm, and unfiltered seawater), phytoplankton growth, and microzooplankton grazing. In this chain-forming diatom dominated system, we found that the majority of TEP was produced in the unfiltered seawater and <200 µm treatments and there were minimal contributions of the <20 µm treatment to bulk TEP measurements. Phytoplankton growth generally exceeded microzooplankton grazing, however, the production of TEP in the <20 and <200 µm treatments was likely reduced due to microzooplankton grazing. Our results improve estimates of TEP production and highlight the importance of considering microbial interactions such as microzooplankton grazing as drivers of TEP and marine snow dynamics.

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Primary Presenter: Mikayla Cote, University of New Hampshire (mikayla.cote@gmail.com)

Authors:

Mikayla Cote, University of New Hampshire  (mikayla.cote@unh.edu)

Elizabeth Harvey, University of New Hampshire  (elizabeth.harvey@unh.edu)