When Time Reveals the Cost: Effects of Long-Term Exposure to Low pH on a Predatory Gastropod

Abstract

Ocean acidification, a direct consequence of anthropogenic carbon dioxide emissions, is among the major challenges for marine organisms. While an increased body of evidence is documenting the negative effects of ocean acidification, most of these studies are still based on short-term exposure. Long-term experiments, studying multiple traits simultaneously, and accounting for short-term local pH variability in the species' habitat are needed. This study investigated the impact of a 310-day exposure to low pH on the banded-dye murex, Hexaplex trunculus (Linnaeus, 1758), a predatory Mediterranean gastropod. Temperature strongly influences the behavior and activity of the banded-dye murex, so we allowed it to vary naturally in this experiment. Our results showed that the net calcification rate was negatively affected by low pH throughout the duration of the experiment. While the banded-dye murexes were able to maintain their total body weight at the beginning of the experiment, it decreased under chronic exposure to low pH. Soft tissue body weight remained unaffected for more than 200 days, followed by a pronounced decrease when exposed to lower pH. No sex-specific differences in response to low pH were observed, but females generally exhibited higher rates of calcification and growth during the winter period, likely due to energy allocation strategies associated with the reproductive cycle. These results suggest that while the banded-dye murex can temporarily reallocate energy to maintain essential physiological functions under low pH, this capacity diminishes over time, revealing physiological limits to long-term stress tolerance. This finding highlights the importance of incorporating long-term, multi-trait experiments in ocean acidification research to better predict species vulnerability, ecosystem-level impacts, and the resilience of coastal marine communities under future climate change scenarios.