The One Piece in the Biological Pump: Krill as Model Organisms for Spatial Variability in Zooplankton-Mediated Carbon Export

Krill (euphausiids) are a dominant zooplankton group and serve as model organisms for understanding zooplankton-mediated carbon export, as many species are cosmopolitan and inhabit multiple ocean basins. Through the production of fecal pellets, euphausiids contribute substantially to the biological carbon pump, yet genus- and species-specific roles, as well as the relative contributions of resident versus migratory communities, remain poorly quantified across regions. This study examines spatial differences in euphausiid-mediated carbon export between the northwest Atlantic and northeast Pacific, two regions with distinct hydrographic conditions, community compositions, and proportions of resident and vertically migrating taxa. Zooplankton samples were collected with diel MOCNESS tows during NSF Ocean Acidification cruises in 2011 (Atlantic) and 2012 (Pacific). Euphausiids are being processed with ZooScan and Ecotaxa to obtain genus-level identifications, size distributions, biovolumes, and abundance estimates. Carbon content and fecal pellet production are calculated by integrating these data with experimentally derived carbon density values and R-based modeling approaches. Depth-specific fecal pellet production will be compared across basins and taxa to assess variability in export magnitude. Preliminary results suggest that differences in euphausiid assemblages, particularly in the relative abundance of migratory (e.g. Euphausia sp.) versus resident (e.g. Stylocheiron sp.) taxa, drive distinct patterns of midwater carbon flux in each region. By leveraging euphausiids as a model group, this study provides new insight into the mechanisms controlling regional carbon export and underscores the importance of incorporating taxon-specific and behavioral traits into biogeochemical and climate models to better predict ecosystem responses to environmental change.

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

Authors:

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

Leocadio Blanco-Bercial, Arizona State University/BIOS  (leocadio@asu.edu)

Amy Maas, Arizona State University/BIOS  (amaas4@asu.edu)

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