Projected declines in zooplankton energy supporting Northwest European Shelf ecosystems

Abstract The abundances of zooplankton species supporting Northeast Atlantic food webs have declined over the past 60 years, and their future is uncertain given continuing climate change. Here, we develop a new high-resolution machine-learning model of key taxa, driven by past ocean conditions and trained on Continuous Plankton Recorder observations. We apply it to an ensemble of regional climate projections for the Northwest European Shelf under the high emissions scenario RCP8.5 to enhance the detectability of a clear signal of climate-driven change in zooplankton abundance. The results project large declines in abundance: ensemble mean of 58%-72% by 2050 and 84%-93% by 2100 for small copepods and large Calanus . The projections are not geographically uniform, with evidence of regional refugia. The future declines are primarily driven by increasing temperature and decreasing salinity and nutrient concentrations, which shift conditions away from the species’ environmental niches and water mass associations. Impacts on food webs would be severe unless alternative zooplankton assemblages emerged to support existing planktivorous fish and their predators.