Recovery mode: Marine protected areas enhance climate resilience of invertebrate species to marine heatwaves

Abstract Marine protected areas (MPAs) can promote population recovery from climate change impacts by reducing local stressors like fishing. However, with extreme climatic events such as marine heatwaves (MHWs) increasing in frequency and duration, it remains unclear whether MPAs enhance resistance to and recovery from these acute perturbations and how resilience varies across species and ecological traits (e.g. sedentary vs. mobile species). We used 15 years (2007–2021) of kelp forest monitoring data in Isla Natividad, Mexico, to assess the impact, resistance and recovery of the 2014–2016 MHWs on the fish and invertebrate communities inside and outside two fully protected marine reserves. The 2014–2016 MHWs, the most intense and persistent observed in Isla Natividad that coincided with the loss of giant kelp forest, impacted invertebrates but not fish biomass. Marine reserves conferred resistance to the MHWs for the invertebrate communities and wavy turban snails ( Megastraea spp.) (J. H. McLean, 1970), as the impact was less severe than in the reference sites. In addition, reserves enhanced the recovery of some species after the MHWs. Inside marine reserves, abalone ( Haliotis spp.) (Linnaeus, 1758) and wavy turban snail (benthic sedentary invertebrates) recovered to pre‐heatwave biomass after 2 years, and spiny lobster ( Panulirus interruptus ) (Randall, 1840) (benthic mobile invertebrate) after 4 years. Outside the reserves, abalone recovered after 3 years, while the other two species never recovered. The warty sea cucumber ( Apostichopus parvimensis ) (H. L. Clark, 1913) population collapsed after the MHWs and never recovered inside or outside the reserve. Remarkably, abalone biomass had an outstanding and sustained recovery inside reserves, with a fourfold increase in biomass after the MHWs, which was nearly three times higher than the recovery reported outside the reserve. No other species had a sustained recovery after the MHWs, neither inside nor outside the reserve. Our analysis of long‐term monitoring data shows that marine reserves cannot fully prevent adverse impacts from extreme climatic events but can enhance species resistance to and recovery from these events. However, benefits conferred by small marine reserves are species‐specific and may be limited to species with limited dispersal and localized population dynamics.