[en] The atmospheric carbon dioxide, whose concentration is constantly increasing since the beginning of the industrial era, dissolves in seawater which results in ocean acidification (OA). The future of marine organisms will depend on their ability to adapt to these physico-chemical changes. OA affects various biological processes, including growth and acid-base balance of the extracellular fluids.
The objective of this study was to evaluate the effect of pH on the growth and the relationship between acid-base regulation and resistance to acidification in the sea urchin Echinometra mathei, a key species in coral reefs.
The study was conducted in two artificial reef mesocosms. For each mesocosm, two experimental tanks, maintained respectively at 400 and 800μatm pCO2, were connected to the main unit. The major physico-chemical parameters of the mesocosms and experimental aquaria were identical. Only pCO2 and pH varied. The growth rate of sea urchins and the evolution of their physiological parameters (pH and pCO2 of the coelomic fluid, respiration rate) were monitored throughout the experiment to detect sensitivity, resistance or acclimatation to OA. Morphometric, mechanical and chemical measurements were also performed on the skeletons of the sea urchins.
