The effects of heatwaves and microplastics and their combination on the Mediterranean bioconstructor coral Astroides calycularis. Book of Abstracts: Bridging knowledge gaps between tropical, temperate, and cold-water coral reefs. Book of abstracts of the 2024 European Coral Reef Symposium.

Shallow marine benthic environments are among the most affected by multiple anthropogenic threats. Here habitat former species, such as corals, exert an important role in maintaining biodiversity and ecosystem functioning, and their heightened vulnerability poses substantial risks to marine ecosystems. It is well-documented that rising sea temperature adversely affects organisms involved in coral reef formation. Specifically, the increased frequency and magnitude of heatwaves (HWs) is becoming a threat globally, particularly in the Mediterranean Sea. This effect of climate change may act synergically or in addition to other anthropogenic stressors, such as plastic pollution, determining further stress to benthic species. This work aims to evaluate the response to HWs and the presence of microplastics (MPs), alone and in combination, on Astroides calycularis, an endemic habitat former Mediterranean coral. This species was already supposed to be affected by HWs and MPs. Here we test its response to both stressors from a biochemical point of view, thanks to a battery of biomarkers. The tested endpoints were antioxidant and biotransformation enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and reactive oxygen species content (ROS)], oxidative damage [lipid peroxidation (LPO)], cellular reserves [protein content (PROT) and glycogen content (GLY)], and mineralization [acid and alkaline phosphatases (AP and ALP, respectively)] responses. Significant response regarding oxidative stress in A. calycularis, both at the level of the enzymes involved in the first line of defence and for the enzymes of detoxification of phase II, was observed in particular for HWs exposure and protein content reduction. MPs alone did not produce statistically significant results whilst the combined effect of MPs and HWs appeared enhanced with respect to HWs only for AP. The biochemical response of bioconstructor species in response to stressors related to climate change and their combined effect with local stressors deserve further investigation.