Risks of ocean acidification in the California Current food web and fisheries: ecosystem model projections

• Published in: Global change biology Vol. 23; no. 4; pp. 1525 - 1539
• Main Authors: Marshall, Kristin N., Kaplan, Isaac C., Hodgson, Emma E., Hermann, Albert, Busch, D. Shallin, McElhany, Paul, Essington, Timothy E., Harvey, Chris J., Fulton, Elizabeth A.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-04-2017
• Subjects: Acidification; Animals; California; California Current; climate change; Copepoda; Decapoda; Ecosystem; ecosystem model; Ecosystems; Fisheries; Food Chain; Food chains; Hydrogen-Ion Concentration; Invertebrates; Mammals; Marine; ocean acidification; Ocean currents; Oceans and Seas; risk assessment; INE, Pacific, California Current; ocean acidification; California Current; ecosystem model; risk assessment; fisheries; climate change
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.13594

The benefits and ecosystem services that humans derive from the oceans are threatened by numerous global change stressors, one of which is ocean acidification. Here, we describe the effects of ocean acidification on an upwelling system that already experiences inherently low pH conditions, the California Current. We used an end‐to‐end ecosystem model (Atlantis), forced by downscaled global climate models and informed by a meta‐analysis of the pH sensitivities of local taxa, to investigate the direct and indirect effects of future pH on biomass and fisheries revenues. Our model projects a 0.2‐unit drop in pH during the summer upwelling season from 2013 to 2063, which results in wide‐ranging magnitudes of effects across guilds and functional groups. The most dramatic direct effects of future pH may be expected on epibenthic invertebrates (crabs, shrimps, benthic grazers, benthic detritivores, bivalves), and strong indirect effects expected on some demersal fish, sharks, and epibenthic invertebrates (Dungeness crab) because they consume species known to be sensitive to changing pH. The model's pelagic community, including marine mammals and seabirds, was much less influenced by future pH. Some functional groups were less affected to changing pH in the model than might be expected from experimental studies in the empirical literature due to high population productivity (e.g., copepods, pteropods). Model results suggest strong effects of reduced pH on nearshore state‐managed invertebrate fisheries, but modest effects on the groundfish fishery because individual groundfish species exhibited diverse responses to changing pH. Our results provide a set of projections that generally support and build upon previous findings and set the stage for hypotheses to guide future modeling and experimental analysis on the effects of OA on marine ecosystems and fisheries.
We used an end‐to‐end ecosystem model to assess potential risks of ocean acidification likely to occur over the next 50 years in the California Current food web and fisheries it supports. We found that mean effects of changing pH at the scale of the ecosystem are generally low, but individual species and functional groups responded more strongly. In particular, some nearshore epibenthic invertebrates and groundfish and the fisheries that target them were most susceptible to pH changes.