Effects of Long Exposure to Different Heatwaves in 2 Reef-forming Species through a Comparison of a Multi-biomarker Approach. Book of Abstracts: ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY – EUROPE (SETAC EUROPE), 34TH ANNUAL MEETING. SCIENCE-BASED SOLUTIONS IN TIMES OF CRISIS: INTEGRATING SCIENCE AND POLICY FOR ENVIRONMENTAL CHALLENGES.

Anthropogenic stressors negatively affect marine organisms, with sessile benthic species being particularly vulnerable, posing significant risks to marine ecosystems. One of the most widespread threats to reef-forming species is rising temperatures. Heatwaves (HWs), characterized by regional warming anomalies, are rising globally, with the Mediterranean Sea experiencing a rapid increase in frequency, magnitude, and severity. This study presents a comparative analysis of the prolonged impacts of HWs on two key reef-forming species: Astroides calycularis, the Mediterranean orange coral, and Ficopomatus enigmaticus, an alien and invasive tubeworm. A long-term exposure of 28 days with two distinct HWs ramps was established. Using as models organisms sessile benthic bioconstructor species known to suffer from HWs-related mass mortality events, and a multi-biomarker approach, the aim is to highlight shared patterns in the biochemical response of habitat forming exposed to different forms of HWs. Parameters assessed included cell membrane damage, cellular reserves, metabolic activity, oxidative status, and biotransformation. The results demonstrated a negative influence of increased temperatures on the biochemical health of both species studied, with a particular lowering of the protein quantity. Despite differences in shape in the two HWs ramps and the two different species investigated, the biomarker results revealed shared patterns in the response of biobuilders to thermal stress. These commonalities in response to climate anomalies, regardless of organisms or HWs characteristics, suggest a wide-ranging impact of increased temperature. Considering the expected increase in marine temperatures in the near future, further investigations are essential to clarify the effects of this stressor on marine organisms, particularly on benthic sessile reef-formers, which are crucial for maintaining biodiversity in their habitats.