Hugues Blanchet

Recent rapid changes in climate and environmental conditions have significantly impacted coastal ecosystem functioning. However, the complex interplay between global and local effects makes it challenging to pinpoint the primary drivers. In a multi‐ecosystem study, we analyzed pluri‐decadal trends of bivalve‐δ 13 C as recorder of global environmental changes. These trends were correlated with large‐scale natural and anthropogenic climate proxies to identify whether coastal biota responded to global effects. Our findings revealed decreasing bivalve‐δ 13 C trends in all sea regions, mainly linked with increased temperature and atmospheric‐CO 2 concentrations, the later generating a decrease in atmospheric‐CO 2 δ 13 C values (Suess effect) because of fossil‐fuel burning. After removing the Suess effect from bivalve‐δ 13 C trends, ongoing global climate variability continues to affect most ecosystems, possibly intensified by combined, interacting regional or local effects. These results highlight the need to consider large‐scale effects to fully understand ecosystem and food web responses to the multiple effects of global change.