Poster Session 4, Thursday, October  6, 11:00–12:40

Poster 44

In situ quantification and classification of marine aggregate and organismal depth distributions during a senescent bloom in the oligotrophic ocean

Understanding the size, distribution, and identity of oceanic particles is critical to modeling biological processes from particle flux to food web dynamics. The ability to capture sinking and suspended particles, either optically or physically, has been key to tracking carbon cycling in the upper ocean for decades. However, classical methods of particle characterization (e.g. nets, traps, and bottles) are often limited by ex situ analysis and prone to altering particles during collection. High-resolution in situ imaging technologies offer promise to expand our understanding of both living and detrital particles from the sea surface to the sea floor. Here, we utilize the Underwater Vision Profiler (UVP5-DEEP) and EcoTaxa taxonomic classification to analyze the abundance, size, and diversity of particles in the oligotrophic North Pacific Subtropical Gyre. Twelve repeated profiles were conducted within an anticyclonic eddy during the demise of a large-scale phytoplankton bloom. Free-floating sediment traps recorded unprecedented rates of particle export (50 mg C m-2 day-1) for the region, while imaging flow cytometry revealed the presence of large diatoms and an array of nitrogen-fixing organisms. Here we present UVP-based estimates of the size, depth-distribution, and abundance of particles over the course of this two-week occupation. We also show the co-occurrence of organisms including foraminifera, copepods, and krill within depth zones of elevated marine snow aggregate concentrations. These results highlight successional patterns of organisms and aggregates along the decline of a mesoscale phytoplankton bloom in the oligotrophic ocean.

*Reece James, University of Hawaii at Manoa, [email protected]

James Allen, University of Hawaii at Manoa, [email protected] 

Fernanda Henderikx, University of Hawaii at Manoa, [email protected] 

Angelicque White, University of Hawaii at Manoa, [email protected]

Daniel Muratore, Georgia institute of Technology, [email protected]

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