Rockpools as Thermal Refuges: Insights from Thermal Records and Heartbeat Monitoring of Intertidal SpeciesClimate Change Refugia

Rita da Silva¹, Hajer Bouraffa¹, Rocío Nieto-Vilela¹, Fernando Lima¹, Rui Seabra¹

¹CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Portugal

Rocky intertidal pools are vital microhabitats that offer critical refugia for marine species. Despite their ecological importance, the extent of their thermal buffering capacity remains poorly understood. Marine organisms in these environments face rapid and extreme temperature changes over a few hours. In such areas, rockpools may serve as refugia, especially important for low-mobility or sessile organisms.
We studied thermal differences between the exterior and interior of natural rockpools across three northern Portuguese shores. Over a two-year period, we collected hourly temperature data both inside and outside rockpools, while documenting key physical characteristics. We found big differences between the recorded temperature outside the rockpool and the temperature inside, and that these differences are especially important during some months of the year.
Building on these field observations, we designed a series of realistic, week-long laboratory experiments. Using individuals collected from both inside and outside the pools, we simulated immersion scenarios and compared them to conditions of exposure to similar temperatures without water immersion. Employing a non-invasive heartbeat monitoring technique, we quantified thermal stress and evaluated the protective role of rockpools in mitigating the impacts of extreme heat exposure.
Our results highlight the importance of rockpools as thermal refuges and their role in helping intertidal species cope with a rapidly changing environment.