A study modeling climate change and anthropogenic nutrient inputs on a coastal California ocean circulation system finds that climatic and nutrient forcing can significantly reshape the biogeochemistry of the system. Climate change is linked to ocean acidification and deoxygenation, and some ocean regions, such as the California Current, which hosts significant fishery activity and biological productivity, may be particularly vulnerable to these detrimental effects. James C. McWilliams and colleagues simulated the circulation of the Southern California Bight, an upwelling current, along with climate drivers and nutrient inputs from rivers, urban wastewater, and atmospheric deposition. Together, the authors found, the combination of climate and nutrient forcing drove a 79% increase in phytoplankton biomass and a nearly 44% increase in subsurface respiration rates in summer. The model results suggest that such eutrophication could seasonally reduce subsurface oxygen concentrations by up to 50 mmol/m3 and reduce pH by 0.09 units. The authors report that the magnitude of modeled reductions in oxygen and pH likely exceed changes in the open ocean since the preindustrial era. According to the authors, the full effects of biogeochemical changes on fisheries, algal blooms, and aquatic vegetation are yet to be uncovered.
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Article #20-18856: "Coastal eutrophication drives acidification, oxygen loss, and ecosystem change in a major oceanic upwelling system," by Fayçal Kessouri et al.
MEDIA CONTACT: James C. McWilliams, University of California, Los Angeles, CA; tel: 310-471-3717; email: jcm@atmos.ucla.edu
Proceedings of the National Academy of Sciences