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Ecological vs. climate uncertainty in future marine ecosystems: lessons learned from krill in a major upwelling region

Fiechter, Jerome1; Cimino, Megan1; Messié, Monique2; Jacox, Michael3; Pozo Buil, Mercedes1; Santora, Jarrod3

Research facility: University of California, Santa Cruz
Published Dec 16, 2025 on Dryad. https://doi.org/10.5061/dryad.3xsj3txtp

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Abstract

Krill is a central organism in the food web of many marine ecosystems and eastern boundary current upwelling regions specifically. Here, a superensemble of climate and ecological models is used to determine drivers of future change, variability, and uncertainty in krill abundance for the California Current. While krill is projected to slowly decrease throughout the 21st century, the long-term trend consistently exceeds natural variability only under extreme warming. Similarly, unprecedented low krill years are expected to progressively increase, but their frequency of occurrence will depend on background abundances tied to low-frequency climate variability. The relative contributions of warming rate and model formulation to projected uncertainty are comparable and reflect latitudinal changes in the magnitude of climate forcing and availability of empirical data to parameterize krill models, thereby warranting a more pragmatic incorporation of anthropogenic and ecological uncertainty sources when projecting the fate of marine ecosystems in a changing climate.