Seawater carbonate chemistry and physiological and mechanical properties of the starfish Asterias rubens in a laboratory experiment@en

The increase in atmospheric CO2 due to anthropogenic activity results in an acidification of the surface waters of the oceans. Its impact will depend on the considered organisms and ecosystems. The intertidal may harbor organisms pre-adapted to the upcoming changes as they face tidal pH and temperature fluctuations. However, these environments will be more affected as shallow waters will face the highest decrease in seawater pH. In this context, the effects of reduced environmental pH on the physiology and tube feet mechanical properties of the intertidal starfish Asterias rubens, a top predator, were investigated during 15 and 27 days. A. rubens showed a respiratory acidosis with its coelomic fluid pH always lower than that of seawater. This acidosis was most pronounced at pH 7.4. Notwithstanding, the starfish showed no significant variations in RNA/DNA ratio of different tissues and in tube feet strength. However, respiration rates were significantly lower for individuals maintained at reduced seawater pH. Within the ocean acidification context, the present results suggest that A. rubens withstands the effects of reduced seawater pH, at least for medium term exposures.人类活动导致大气二氧化碳浓度升高，进而引发海洋表层水体酸化。其影响因所研究的生物与生态系统而异。潮间带生境的生物因长期经历潮汐带来的pH值与温度波动，或已预适应未来的环境变化。但浅海海域的海水pH降幅最大，因此这类生境反而会受到更显著的影响。在此背景下，本研究针对顶级捕食者——潮间带海星多棘海盘车（Asterias rubens），开展了为期15天与27天的暴露实验，探究环境pH降低对其生理状态与管足机械特性的影响。实验结果显示，多棘海盘车出现了呼吸性酸中毒，其体腔液pH始终低于海水pH，且该酸中毒在pH 7.4的环境下最为显著。尽管如此，该海星不同组织的RNA/DNA比值以及管足力量均未出现显著变化。但处于低pH海水环境中的个体，其呼吸速率显著降低。综合海洋酸化的研究背景，本实验结果表明，多棘海盘车至少可耐受中期的低pH海水胁迫。