Season-dependent effects of ocean warming on the physiological performance of a native and a non-native sea anemone

The effects of ocean warming on the physiological performance of marine organisms have been widely studied. However, few studies have considered the relevance of seasonal acclimation to elevated temperatures and whether native and non-native species have similar tolerances to warming. We tested the hypotheses that the susceptibility to warming in two species of sea anemones from temperate latitudes is (i) higher in winter than in summer, and (ii) higher in the native than in the non-native species. Seasonal variability in the upper thermal tolerance limit of Anthothoe chilensis (native) and Anemonia alicemartinae (non-native) individuals from the northern-central coast of Chile was assessed in laboratory experiments during the austral winter 2015 and summer 2016. In line with our predictions, seawater warming (up to 16 degrees C above natural levels) significantly suppressed individual performance proxies such as survival and asexual reproduction (longitudinal fission) in the native species, but not in the non-native species. However, asexual reproduction in the non-native sea anemone was rare across warming treatments, and the native species showed a stronger capacity to detach from the substratum under adverse thermal conditions. Negative effects of warming on survival and fission were evident only in winter, when asexual reproduction is more intense in these taxa. Finally, water temperatures of 30 degrees C or more were lethal for both native and non-native sea anemones. These results show that the non-native species may have a broader thermal tolerance (in terms of survival) than the native taxonomically related species, but the latter displays behavioral adaptations to avoid adverse conditions of high temperatures. We suggest that knowledge about life history traits related to seasonal variations in water temperature and the invasion status of a species can help to predict its performance in a warming ocean.