Conclusion
To anticipate the consequences of climate change on marine ecosystem function and services (e.g., food provisioning and climate regulation through carbon sequestration) it is critical to understand how changes in ocean productivity and temperature may affect the upper trophic levels of marine ecosystems. Our large-scale empirical investigation showed a pronounced latitudinal increase in demersal fish community biomass from the subtropics to the poles. The changes in demersal community biomass are linked to differences in temperature, fishing, and ocean productivity. The observed negative relationship between temperature and community biomass indicates that the long-term impacts of climate warming on community biomass will be negative. This finding is consistent with model predictions of fish biomass (Lotze et al. 2019; Tittensor et al. 2021). Hence, our results provide an important empirical basis to formally validate and ground truth such model-based predictions in order to evaluate sound and robust management actions in the face of global change.