Foul?weather friends: Modelling thermal stress mitigation by symbiotic endolithic microbes in a changing environment

Temperature extremes are predicted to intensify with climate change. These rapidly emerging as a powerful driver of species distributional changes the capacity disrupt functioning and provision services entire ecosystems, particularly when they challenge ecosystem engineers. The subsequent search for robust framework forecast consequences these mostly ignores within-species variation in thermal sensitivity. Such can be intrinsic, but also reflect interactions. Intertidal mussels important engineers that host symbiotic endoliths their shells. unexpectedly act conditionally beneficial parasites enhance host's resistance intense heat stress. To understand how this relationship may altered under environmental change, we examined conditions which it becomes advantageous by reducing body temperature. We deployed biomimetic sensors (robomussels), built using shells (Mytilus galloprovincialis) were or not infested endoliths, at nine European locations spanning temperature gradient across 22°of latitude (Orkney, Scotland Algarve, Portugal). Daily wind speed solar radiation explained maximum difference between non-infested robomussels; largest occurred low high radiation. From robomussel data, inferred differences during known heatwaves induced mass mortality mussel Mytilus edulis along coast English Channel summer 2018 quantify advantage endolith infestation extremes. Under conditions, provided buffering 1.7°C 4.8°C. Our results strongly suggest sustainability intertidal beds will increasingly depend on endoliths. More generally, work shows models indicate sensitivity global warming modulated interactions, an host–symbiont example.