Book of Abstracts of the 14th International Temperate Reefs Symposium (ITRS 2025). 1-5 July 2025, Brest, France. Evaluation of the biochemical effects of marine heatwaves on the biobuilder species Ficopomatus enigmaticus through a multi-biomarker approach

Sessile benthic organisms are increasingly threatened by global environmental changes, particularly rising temperatures. Using a multi-biomarker approach, this study examined the effects of long-term (30-day) exposure to two distinct types of marine heatwaves (MHWs) on the reef-building tubeworm Ficopomatus enigmaticus. Two different MHW scenarios were recreated to assess which type of thermal stress, prolonged or short but repeated, would have a greater impact on sessile bioconstructors. The first scenario involved two short and repeated heatwave events, each lasting 4 days, with a 5°C increase in temperature compared to the control (20 °C). Each heatwave included a gradual increase and decrease in temperature of 1 °C per day for 5 days. The second scenario involved a single heat wave in which the temperature was gradually increased by 0.5 °C per day, first reaching a 3 °C increase over the control (20 °C), which was maintained for 5 days, then reaching a peak of 4 °C, which was maintained for 7 days. After this peak, the temperature was gradually reduced in the second half of the experiment, following the same temperature ramp per day but in reverse. To assess the health status of the bioconstructor species under study, biomarkers of cell membrane damage, antioxidant enzyme activity, metabolic function, neurotoxicity, and DNA integrity were evaluated. Exposure to MHW led to alterations in metabolic activity, including an increase in glutathione S-transferase and a decrease in protein content, suggesting a reduction in energy reserves. Some analyses are still ongoing. These results highlight the impact of climate change-related stressors on biogenic reef-building organisms in marine and brackish environments.