Ocean acidification is predicted to have significant effects on benthic calcifying invertebrates, in particular on their early developmental stages. Echinoderm larvae could be particularly vulnerable to decreased pH, with major consequences for adult populations. The objective of this study was to understand how ocean acidification would affect the initial life stages of the sea urchin Paracentrotus lividus, a common species that is widely distributed in the Mediterranean Sea and the NE Atlantic. The effects of decreased pH (elevated PCO2) were investigated through physiological and molecular analyses on both embryonic and larval stages. Eggs and larvae were reared in Mediterranean seawater at six pH levels, i.e. pHT 8.1, 7.9, 7.7, 7.5, 7.25 and 7.0. Fertilization success, survival, growth and calcification rates were monitored over a 3 day period. The expression of genes coding for key proteins involved in development and biomineralization was also monitored. Paracentrotus lividus appears to be extremely resistant to low pH, with no effect on fertilization success or larval survival. Larval growth was slowed when exposed to low pH but with no direct impact on relative larval morphology or calcification down to pHT 7.25. Consequently, at a given time, larvae exposed to low pH were present at a normal but delayed larval stage. More surprisingly, candidate genes involved in development and biomineralization were upregulated by factors of up to 26 at low pH. Our results revealed plasticity at the gene expression level that allows a normal, but delayed, development under low pH conditions.
↵† Present address: Faculty of Science, University of Technology, Sydney, P.O. Box 123, Broadway, NSW 2007, Australia
The IAEA is grateful for the support provided to its Marine Environment Laboratories by the Government of the Principality of Monaco. S.D. is funded through the Linnaeus Centre for Marine Evolutionary Biology at the University of Gothenburg and supported by a Linnaeus grant from the Swedish Research Councils VR and Formas. This work is a contribution to the ‘European Project on Ocean Acidification’ (EPOCA), which received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 211384.
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