Low temperature exposure determines performance and thermal microhabitat use in an intertidal gastropod (Littorina scutulata) during the winter

Abstract

Small-scale spatial variation in temperature is an important attribute of many habitats, as spatial thermal refugia may allow organisms to avoid some negative consequences of thermal extremes. Although the ecological importance of thermal refugia in intertidal habitats is well-known in summer, the relative availability, effectiveness, and ecological relevance of thermally benign microhabitats in the winter is poorly understood. Here, we explored small-scale thermal variability on a temperate rocky coastline during winter, and the relevance of these thermal patterns to Littorina scutulata, a common intertidal gastropod. Sheltered microhabitats, including crevices, undersides of boulders, and areas beneath algal canopy, were all warmer than surrounding exposed areas during winter low tides. L. scutulata was able to recover relatively quickly from exposure to low temperatures down to -3°C, but performance costs began to accrue at lower temperatures. However, the presence of a refuge habitat buffered the negative effects of cold temperatures, and sheltered L. scutulata regained mobility more quickly than conspecifics on exposed surfaces. Further experiments demonstrated that L. scutulata were more frequently found in thermal refugia when previously exposed to low temperatures, but not when exposed to milder temperatures. Our results suggest that realistic low temperatures can impose important costs on intertidal species such as L. scutulata, but the availability of thermal refugia coupled with behavioural adaptations can allow species to reduce many such costs. Just as in summer, thermal refugia in winter may be important for the distribution and abundance of intertidal species and the diversity and function of coastal ecosystems.

An integrated, multi‐level analysis of thermal effects on intertidal molluscs for understanding species distribution patterns

“…Furthermore, an increasing number of studies are demonstrating the importance of small‐scale spatiotemporal variations in habitat conditions (Denny et al ., 2011; Bennett et al ., 2015; Choi et al ., 2019) that create a potential for behaviourally based relief from thermal stress (Gilman et al ., 2015; Choi et al ., 2019; Han, Wang & Dong, 2020; Hayford et al ., 2021). These behavioural responses are important at both high (Dong et al ., 2017) and low (Reid & Hartley, 2021) temperatures. For example, escape from cold stress during winter low tides by the intertidal gastropod Littorina scutulata was enabled by movement into slightly warmer habitats beneath boulders and the algal canopy (Reid & Hartley, 2021).…”

Behavioral repertoire of high‐shore littorinid snails reveals novel adaptations to an extreme environment

“…Aggregation and crevice occupation may also reduce the risk of dislodgement by wave action, which is on average significantly higher in the cool season on Hong Kong shores (Apps & Chen, 1973). As such, the function of these aggregations, allowing the snails to reduce activity, possibly depress their metabolism, and remain safe from high wave action, may be fundamentally different from their function in the hot season (see also Reid & Harley, 2021).…”

“…Stress‐mitigating behaviors play a key role in the survival of mobile intertidal species when thermal and desiccation stresses become severe during emersion periods (Garrity, 1984; Harper & Williams, 2001; Hayford et al., 2015; Reid & Harley, 2021; Williams & Morritt, 1995). Most species are adapted to time their periods of activity and inactivity to minimize exposure to thermal stress.…”

Ocean acidification increases susceptibility to sub-zero air temperatures in ecosystem engineers (Mytilus sp.): a limit to poleward range shifts

“…While the vast majority of OA and climate change research has focused on lower latitude systems, studies have rarely considered the impacts on species at their poleward edge. The poleward edge of subtidal ectotherms is determined by low water temperatures (Sunday et al, 2012), however the distribution of intertidal species is also controlled by their capacity to tolerate sub-zero air temperatures during emersion (Kennedy et al, 2020; Reid and Harley, 2021; Thyrring et al, 2019). On rocky shores, canopy-forming macroalgae shelter the understory communities from extreme sub-zero air temperatures (Sejr et al, 2021), and where cold enough, an ice foot forms on the rocky surface, creating a warmer protective microhabitat increasing survivorship of intertidal organisms residing below (Scrosati and Eckersley, 2007; Thyrring et al, 2017a).…”

“…While the vast majority of OA and climate change research has focused on lower latitude systems, studies have rarely considered the impacts on species at their poleward edge. The poleward edge of subtidal ectotherms is determined by low water temperatures (Sunday et al, 2012), however the distribution of intertidal species is also controlled by their capacity to tolerate sub-zero air temperatures during emersion (Kennedy et al, 2020;Reid and Harley, 2021;Thyrring et al, 2019).…”