Impacts of increasing temperature due to global warming on key habitat-forming species in the Mediterranean sea: Unveiling negative biotic interactions

Temperature plays a pivotal role in prey-predator interactions, acting as a potent source of disturbance that can reshape the strengths of interactions between prey and predators. This alteration can subsequently destabilize populations and trigger shifts in the dynamics of ecosystems and food webs. The rising temperatures are exerting significant impacts on Mediterranean biodiversity and community structure. These changes have the potential to influence predation dynamics among co-occurring species, each with distinct responses to the changing climate. Here, we present a case study that delves into the impact of temperature on the biotic interaction between a thermophilic predator polychaete (Hermodice carunculata) and a threatened, key structuring coral species (Astroides calycularis). Through manipulative laboratory experiments, we explored three main aspects: i) polychaete Prey Preference: the prey preference of H. carunculata, revealing that it indeed displays a distinct preference for feeding on A. calycularis over other options. ii) Temperature Effect on Predator Ingestion Rate: we examined how temperature influences the ingestion rate of the predator. Notably, we found that the predator's predation performance peaks at a temperature of 25.6 ºC, which is in close proximity to the upper thermal limit of the coral. iii) Prey Metabolic Response: when exploring the metabolic response of the prey to contact with the predator, we observed an immediate reaction from the prey. This response led to a decline in the coral's feeding capability and an alteration in its metabolic functioning, effectively worsening the coral's overall performance. These findings underscore that H. carunculata not only displays a preference for consuming A. calycularis but also exhibits optimal predation performance at a temperature near the coral's upper thermal threshold. Furthermore, the prey's response to the presence of the predator has rapid and detrimental consequences, negatively impacting the coral's metabolic function. Comprehending the repercussions of environmental change on biotic interactions holds paramount importance. It allows us to forecast and manage the trajectory and conservation efforts of biodiversity under current and projected climate change conditions.