Side matters: Microhabitat influence on intertidal heat stress over a large geographical scale

The present study examined the relative magnitudes of local-scale versus large-scale latitudinal patterns of intertidal body temperatures, using data loggers mimicking limpets from the genus Patella. Over approximately 18 months, loggers collected continuous 30-minute resolution data on body temperatures at a variety of microhabitats on 13 rocky shores along the Atlantic coast of the Iberian Peninsula. Data showed that during low tide, body temperatures of sun-exposed animals routinely reached much higher temperatures than their counterparts attached to north-facing, shaded surfaces. Sunny versus shaded differences were consistently larger than the variability associated with the seasons and with shore level. Moreover, daily variation far exceeded that observed when considering only averaged sea surface temperature. Therefore, analysing temperature at the scales of the organisms may provide a wealth of information more suited to understand and model the distribution of intertidal species under present and future climatic scenarios.

Research Highlights
► We examined patterns of intertidal body temperatures along a wide latitudinal range.
► We focused on local- vs. large-scale patterns during high and low tide periods.
► Sun-exposed organisms were routinely subjected to remarkably high temperatures.
► Differences between sunny and shaded habitats overwhelmed thermal variability.
► Intertidal thermal stress during low tide may be underestimated when using SST alone.