Mitigation of intertidal temperature extremes by algal canopies

In a world experiencing rapid warming, species must adapt to changing conditions, shift their range, or face extinction. Structural complexity within ecosystems can provide microclimate buffering, aiding persistence. Coastal areas have long recognized macroalgae as ecosystem engineers that can moderate thermal extremes, though the extent of this buffering has often gone unmeasured.

The study aimed to quantify thermal buffering provided by intertidal macroalgae using high-frequency, high-spatial-resolution in situ temperature logging. Comparisons were made between microclimates beneath algal cover and on bare rock across two tidal levels, two solar exposures, and two seasons at six shores within a biogeographical transition zone.

Results showed that thermal buffering was highly heterogeneous across the study area, influenced by species identity, algal cover, tidal level, and solar exposure. This created a complex thermal mosaic, with even small algal specimens offering measurable buffering. Factors such as latitude, lower tidal position, reduced solar exposure, and algal cover each played a role in moderating thermal conditions.

Collectively, these elements provided an average cooling of approximately 4°C. The findings emphasize the significance of fine-scale habitat heterogeneity in shaping thermal exposure and identify factors that could be integrated into local climate adaptation strategies, contributing to coastal conservation and restoration.