Multigenerational effects of ocean warming on copepod physiology, nutritional value, and epigenetics : evidence for reversible and adaptive stress responses

Climate change and the associated rise in ocean temperatures can have serious effects on marine invertebrates, including copepods, which play a critical role in aquatic food webs. This study investigates the multigenerational effects of gradual ocean warming and acute thermal stress on Nitocra spinipes, a harpacticoid copepod widely used in ecotoxicological research. We examined changes in key life-history traits: prosome length, respiration rate, and clutch size, as well as global DNA methylation and nutritional quality across five generations. Results show that the pace and duration of warming critically influence biological responses. Gradual temperature increases allowed for partial adaptive responses over generations, while acute heat stress led to marked reproductive collapse. Reproductive success was the most affected trait, though signs of recovery were observed when temperature stress was removed, indicating potential for resilience. Global DNA methylation patterns acted as a reversible epigenetic marker of thermal stress. Additionally, warming induced biochemical shifts, reflected in decreased docosahexaenoic acid (DHA) and increased palmitoleic acid levels. These findings highlight the vulnerability of N. spinipes to rising temperatures and underscore the importance of considering both gradual and abrupt thermal changes, as well as epigenetic mechanisms, in assessing meiobenthos responses to climate change.