Long‐Term Exposure of Bivalves to Ocean Acidification and Warming Under Ecologically‐Realistic Conditions Reveals Risks for Aquaculture by 2050 in the Mediterranean

Abstract Bivalve mollusks are vital to coastal economies and food security, yet the impact of ocean warming and acidification on aquaculture remains unclear due to a lack of ground truth data on future production. Most experimental studies rely on short‐term, single‐factor experiments in stable and food‐unlimited environments, making it difficult to provide practical guidance to growers and decision‐makers. To address this knowledge gap, we developed a land‐based automated system to expose bivalves to future climate scenarios under field‐realistic conditions using unfiltered, ambient seawater, assessing survival, growth, reproduction, and next‐generation development. Here we present the first results of exposing Pacific oysters and Mediterranean mussels, the two most cultivated species in the Mediterranean area, to present conditions and projected scenarios for the years 2050, 2075, and 2100. For the first time, our results reveal that future warming and acidification conditions have a dramatic impact on the production yield of oysters and mussels. Oysters exposed to conditions projected for 2100 exhibited a 7% reduction in survival and a 40% reduction in growth rate, along with lower reproductive maturity, which in turn negatively affected the early development of their offspring. Mussels are already experiencing summer temperatures above their upper thermal limits, with around 40% mortality observed under current conditions and near‐total mortality under those projected for 2050. These patterns reflect sporadic mass‐mortality events reported elsewhere in the Mediterranean and indicate that mussel farming in the region could be severely compromised by mid‐century. Our results urgently call for the development of adaptation strategies in the Mediterranean.