Responses of Marine Trophic Levels to the Combined Effects of Ocean Acidification and Warming

Abstract Marine organisms are simultaneously exposed to anthropogenic stressors associated with ocean acidification and warming with likely interactive effects. Although new research has started to uncover how marine primary producers, herbivores, and predators are responding to climate change, we still do not have a comprehensive understanding of general patterns across trophic levels in response to multiple stressors. Yet, marine species from different trophic levels with dissimilar characteristics and evolutionary history are likely to respond differently to climatic stressors.Our study represents the first meta-analysis of multiple stressor studies to target comparisons of mean effects and identification of interaction types among marine trophic levels. The meta-analysis revealed a number of key results: (1) Predators are the most tolerant level in response to individual and combined effects of ocean acidification and warming; (2) synergistic interactions (16%) are less common than additive (40%) and antagonistic (44%) interactions; (3) interaction types vary among trophic levels, with the proportion of synergistic interactions decreasing with increasing trophic level; (4) for interactive effects, calcifying and non-calcifying species show similar patterns across trophic levels; and (5) trophic levels respond to stressors differently along a latitudinal gradient. This study emphasizes the importance of considering stressor interactions and trophic levels in conservation actions. Contrary to many predictions, which has suggested synergistic effects predominate multiple stressors, this research demonstrates that the interaction effect between ocean acidification (OA) and ocean warming (OW) can sometimes mitigate or even reduce negative effects, with additive and antagonistic interactions dominating. Our study provides new knowledge for understanding how multiple stressors may interactively affect marine trophic levels and highlighting the need for further research and a deeper understanding of multiple stressors in conservation efforts.