REFINING FECAL PELLET CARBON DENSITY ESTIMATES OF KEY ZOOPLANKTON TAXA IN THE SARGASSO SEA

Zooplankton play a fundamental role in marine ecosystems, facilitating carbon export by producing fecal pellets that transport organic carbon from surface waters to the deep ocean. This process significantly impacts carbon sequestration and oceanic carbon cycling. Global models that estimate carbon flux using the carbon density of zooplankton fecal pellets often overlook regional variability, potentially leading to inaccurate predictions of carbon export. This study seeks to improve the accuracy of these models by quantifying the carbon density of key zooplankton taxa in the Sargasso Sea, an oligotrophic region with diverse zooplankton communities. Zooplankton were collected in March 2023 during both day and night MOCNESS tows conducted at the Bermuda Atlantic Time Series (BATS) site. The sampling focused on important taxa such as euphausiids, salps, pteropods, and the copepod Pleuromamma xiphias. After sorting, animals were allowed to excrete and fecal pellets were sampled for a combination of image-based methods and CHN elemental analysis. Results revealed substantial discrepancies between experimental carbon density values and predictions from global models. These variations substantially alter the prediction of carbon flux inferred from either zooplankton abundance or image based analysis of trap particles. This study underscores the critical importance of integrating localized, taxa-specific data into biogeochemical models to enhance our understanding of midwater carbon flux and its broader implications for the global carbon cycle.

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Primary Presenter: Yuuki Niimi, Arizona State University (yniimi@asu.edu)

Authors:

Yuuki Niimi, Arizona State University  (yniimi@asu.edu)

Leocadio Blanco-Bercial, Arizona State University/Bermuda Institute of Ocean Science  (leocadio@asu.edu)

Amy Maas, Arizona State University/Bermuda Institute of Ocean Science  (amy.maas@asu.edu)

Susanne Neuer, Arizona State University  (Susanne.Neuer@asu.edu)