Controls on Planktonic Ecosystem Structure in Eastern Boundary Upwelling Systems
Speaker: Jordyn Moscoso
Institution: UCLA Atmospheric & Oceanic Sciences
Location: Zoom Seminar
Eastern boundary upwelling systems (EBUSs) are among the most ecologically diverse and productive regions in the ocean. EBUSs account for approximately 1% of the global ocean by area but yield nearly 20% of the global fish catch. Thus, consequences to changes in productivity in EBUSs anticipated under climate change span from regional socioeconomic stability to global food security.
Ecological responses to wind-driven upwelling in EBUSs have long been studied, yet questions still remain on the controls of the cross-shore (zonal) ecosystem composition. Previous studies indicate that large plankton contributes to a majority of the biomass near the coast where upwelling supports high levels of productivity, whereas small plankton accounts for most of the biomass in offshore regions with low productivity. However, little is known about the responses to zonal ecosystem composition to perturbations in the large-scale physical forcing.
In this talk, I present a new quasi-2D, idealized physical model of EBUSs, coupled with a size-structured ecosystem model, where an organism’s size is chosen to represent ecological diversity. With this coupled physical-biogeochemical model, we characterize the zonal ecosystem composition and responses to perturbations in wind-forcing and offshore nutrient availability. We find increases in the strength of the wind, and shoaling of the nutricline – resulting in more nutrients and biomass on the shelf – support larger average plankton both near the coast and offshore. These results are an important step toward understanding the sensitivities in the zonal structure of plankton communities and higher food-web structure in EBUSs.
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