Survival of the Coolest: How habitat-forming species convey temporal stability of microclimates and communitiesClimate Change Refugia

Ze Hoe Lee¹, Melanie Bishop¹, Nina Schaefer¹

¹Macquarie University, Australia

Climate warming threatens the survival of intertidal species, many of which live close to their thermal maxima. Persistence of intertidal species may depend on cool microclimates provided by topographical features or habitat-forming species, that provide habitat complexity. At large scales habitat complexity is positively correlated with biodiversity, but at small scales, positive complexity-biodiversity relationships may depend on the efficacy of particular habitat geometries at providing protection to inhabitants from environmental stress, as well as predators. This study assessed the relative efficacy of six habitat-forming species - four species of algae, a mussel and a barnacle - in creating thermally stable and protective microclimates that facilitated associated biodiversity across summer and winter of two years. We hypothesised that thermal amelioration by habitat-forming species would vary as a function of inter- and intra-specific variation in morphological traits such as biomass, canopy height, and fractal dimension, as well as the height on the shore at which the habitat-former was found. Further, we hypothesised that the associated community structure of habitat-forming species would be less temporally variable and overall biodiversity greater for habitat-formers providing more temporally stable microclimates. The results of this study will assist in developing conservation strategies targeting climate change adaptation of intertidal biodiversity.