Physiological Stress Induced by an Invasive Filamentous Green Alga on a Native Sponge from a Coastal Mediterranean Lagoon (Balearic Islands).

This study reports the physiological effects of the invasive alien species Batophora occidentalis within a small lagoon in the Balearic Islands. This study aims to determine whether the presence of newly colonizing invasive macroalgae causes physiological effects on the sessile Porifera species Sarcotragus spinosulus through the application of biochemical markers and metabolomic fingerprinting. Sections of 27 different individuals were collected at three representative sites (N = 9 in each site) of varying degrees of epibiont colonisation (high, low, and absent). The activation of antioxidant enzymes for catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GRd) was observed between individuals that were highly affected by B. occidentalis in addition to the detoxification mechanism for glutathione s-transferase (GST). In terms of oxidative damage, MDA levels were found to be nonsignificant, although those individuals characterised by high epibiont colonisation reported higher levels than those in areas where B. occidentalis was not present. Furthermore, significant differences were observed in the metabolomic fingerprinting of the different levels of epibiont colonisation, an indication B. occidentalis is causing changes in chemical and metabolomic characteristics in S. spinosulus. These findings highlight the need for targeted conservation strategies to mitigate the ecological impact of this invasive species in Mediterranean coastal lagoons.