RELATIONSHIPS BETWEEN THE ORGANIC COMPOSITION OF PARTICULATE AND DISSOLVED ORGANIC MATTER IN AN OLIGOTROPHIC WATER COLUMN

The production and consumption of particulate organic matter (POM) in the epipelagic ocean control the quantity of organic matter available for export and sequestration in the deep ocean via the passive flux of particles. Historically, models have considered respiration of POM as the main process attenuating sinking flux, and recent models also better account for disaggregation processes. However, there has been less focus on POM flux attenuation via solubilization of POM to dissolved organic matter (DOM). Largely through the hydrolytic enzymatic activity of bacteria, solubilization decreases POM inventories while potentially both contributing to a long-lived pool of DOM and providing substrates for short-term microbial uptake. Recently, compound-specific isotopic analysis of amino acids (CSIA-AA) has been used to identify POM size fractions and water column depths where solubilization of POM leaves isotopic imprints on the remaining particles. Examining multiple seasons and diel patterns at the Bermuda Atlantic Time-series Study site, we compare size-fractionated POM and DOM composition (individual amino acids and carbohydrates), along with CSIA-AA results from particles that identify solubilization mechanisms linking the particulate and dissolved amino acid pools. We also evaluate the community composition of particle-attached bacteria likely involved in solubilization processes. We discuss how the observed composition of DOM and POM results from the dynamics of cell exudation, lysis, and particle solubilization and suggest new directions for resolving these dynamics.

Presentation Preference: Oral

Primary Presenter: Hilary Close, University of Miami (hclose@miami.edu)

Authors:

Hilary Close, Department of Ocean Sciences, Rosenstiel School of Marine, Atmospheric, and Earth Science, University of Miami  (hclose@miami.edu)

Lillian Henderson, Department of Ocean Sciences, Rosenstiel School of Marine, Atmospheric, and Earth Science, University of Miami  (lillianhenderson05@gmail.com)

Dailen Jeng, Department of Ocean Sciences, Rosenstiel School of Marine, Atmospheric, and Earth Science, University of Miami  (dlj73@earth.miami.edu)

Jacqueline Comstock, Marine Science Institute, Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara  (jcomstock@ucsb.edu)

Chance English, Marine Science Institute, Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara  (cje@ucsb.edu)

Shuting Liu, Department of Environmental & Sustainability Sciences, Kean University  (liushut@kean.edu)

Craig Carlson, Marine Science Institute, Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara  (craig_carlson@ucsb.edu)