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Oceanography Seminar

October 18, 3:00pm - 4:00pm
Mānoa Campus, MSB 100

Hilary Close
SOEST Young Investigator
and NOAA Climate and Global Change Postdoctoral Fellow

Abstract:Rethinking the roles of particulate organic matter in the era of microbial oceanography: lessons from stable isotopes and sampling methodology

Microbes, including Bacteria, are recognized as globally important mediators of elemental transformations in the marine water column, but the contribution of bacterial biomass to the export of organic matter in the ocean is rarely considered to be quantitatively significant. Recent studies have uncovered pathways by which biomass of the smallest plankton in the water column may contribute to export; geochemical evidence for this contribution remains sparse.

Using the largest data set to date for natural 13C content of individual lipids from the marine water column, I compare an exclusively microbial size class of particulate organic matter (POM) to conventional “suspended” POM. Heterogeneity in the isotopic values of intact lipids is associated with particle size and lipid polarity, and by extension, must arise from the composition of the plankton community. I will present a simple model to quantitatively explore the sinking vs. in situ origin of submicron POM in the Eastern Tropical North Pacific, also highlighting the roles of low-oxygen microbial metabolisms and metazoan migration in contributing to POM at mesopelagic depths.

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Oceanography, Mānoa Campus

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