Colorado mountains
From Long-Term Data to Understanding: Toward a Predictive Ecology
2015 LTER ASM Estes Park, CO - August 30 - September 2, 2015

Plankton ecosystem dynamics in a cyclonic eddy in the California Current System

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Fanny Chenillat
peter JS Franks
pascal Riviere
xavier Capet
nicolas Grima
bruno Blanke

Eastern boundary upwelling systems (EBUS) are characterized by high biological production along the coast, contrasting with oligotrophic waters offshore. This cross-shore gradient is affected by intense mesoscale eddy activity. Eddies that are formed at the coast move offshore, entraining and redistributing nearshore nutrients and planktonic organisms. High planktonic biomass can be found in these eddies months after detaching from the coast. The mechanisms driving these patterns and their ecological impacts in EBUSs are still in debate. We focus our analysis on the Southern California Bight (SCB), part of the Californian EBUS. To characterize and understand the influence of mesoscale eddies on planktonic ecosystems in the SBC, we use a numerical approach coupling the Regional Ocean Modeling system (ROMS), at 5 km horizontal resolution, with a multiple size class planktonic ecosystem model (NEMURO). Combining Eulerian and Lagrangian analyses, we were able to follow one specific cyclonic eddy formed in the Southern California Bight as it detached from the coast and migrated offshore. Within this tracked eddy, we characterized the ecosystem dynamics in time and space and aimed to elucidate the mechanisms that influence the planktonic ecosystems trapped in eddies, and the relative contribution of horizontal and vertical advection in determining local production.