Abstract
Predicting responses of coastal ecosystems to altered sea surface temperatures (SST) associated with global climate change, requires knowledge of demographic responses of individual species. Body size is an excellent metric because it scales strongly with growth and fecundity for many ectotherms. These attributes can underpin demographic as well as community and ecosystem level processes, providing valuable insights for responses of vulnerable coastal ecosystems to changing climate. We investigated contemporary macroscale patterns in body size among widely distributed crustaceans that comprise the majority of intertidal abundance and biomass of sandy beach ecosystems of the eastern Pacific coasts of Chile and California, USA. We focused on ecologically important species representing different tidal zones, trophic guilds and developmental modes, including a high-shore macroalga-consuming talitrid amphipod (Orchestoidea tuberculata), two mid-shore scavenging cirolanid isopods (Excirolana braziliensis and E. hirsuticauda), and a low-shore suspension-feeding hippid crab (Emerita analoga) with an amphitropical distribution. Significant latitudinal patterns in body sizes were observed for all species in Chile (21° - 42°S), with similar but steeper patterns in Emerita analoga, in California (32°- 41°N). Sea surface temperature was a strong predictor of body size (-4% to -35% °C-1) in all species. Beach characteristics were subsidiary predictors of body size. Alterations in ocean temperatures of even a few degrees associated with global climate change are likely to affect body sizes of important intertidal ectotherms, with consequences for population demography, life history, community structure, trophic interactions, food-webs, and indirect effects such as ecosystem function. The consistency of results for body size and temperature across species with different life histories, feeding modes, ecological roles, and microhabitats inhabiting a single widespread coastal ecosystem, and for one species, across hemispheres in this space-for-time substitution, suggests predictions of ecosystem responses to thermal effects of climate change may potentially be generalised, with important implications for coastal conservation.
Highlights
Climate change is considered to be one of the most significant contemporary threats to maintenance of global biodiversity, with major consequences predicted for distribution and abundance and the structure and function of plant and animal communities [1,2,3,4,5]
Our analyses demonstrate consistent macro-scale patterns of body size for broadly distributed intertidal animals of sandy beach ecosystems in the northern and southern hemispheres of the eastern Pacific coast
Those of Dugan et al [37], suggest that local habitat features that do not vary with latitude may contribute to variation in body size in some life stages, most of the variation observed in body size of these intertidal crustaceans was best explained by surf zone water temperature alone
Summary
Climate change is considered to be one of the most significant contemporary threats to maintenance of global biodiversity, with major consequences predicted for distribution and abundance and the structure and function of plant and animal communities [1,2,3,4,5]. In the ocean, reported effects of increased water temperatures extend from the tropics to the poles [6, 8,9,10,11,12,13,14], with consequences for biodiversity, food webs, ecosystem functioning and the provision of ecosystem goods and services. Predicting ecological responses to the effects of altered water and air temperatures, sea level rise, coastal squeeze, storminess and acidification on organismal, population and community processes is important for coastal ecosystems which occupy a narrow strip at the edge of land and sea [18,19,20,21]
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