No apparent impact of moderate temperature increase on growth and fecundity in the sea star Asterias rubens

Sea stars are considered as both keystone predators and pests for shellfish fisheries and aquaculture. Recurrent outbreaks after mild winters in temperate ecosystems suggest that the reproductive success of sea stars may be positively impacted by rising ocean temperatures induced by climate change, although previous studies have shown that the strongest projected increase of temperature may be detrimental to them. The impact of a moderate rise of ocean temperature on growth and fecundity of the sea star Asterias rubens was investigated. Males and females were exposed for 6 months either to monthly temperatures from the 1995-2014 periods or to these temperatures elevated by 1.5 °C, as projected at the end of the century by the "middle of the road" scenario of greenhouse gas emissions. Growth (measured as the change in arm length and body weight between the beginning and the end of the experiment), pyloric caeca weight, gonad weight, pyloric index, gonadosomatic index, gamete concentration (number of oocytes or sperm per gram of gonad), fecundity (number of oocytes or sperm per individual) and oocyte shape (volume and sphericity) were assessed at the end of the experimental period. No effect of temperature was observed for any of the investigated variables. Overall, these results indicate that A. rubens may not be impacted by the moderate increases of temperature that might occur if policies promoting the reduction of greenhouse gas emissions would be implemented.