The increasing atmospheric CO₂ concentration in the last few decades has resulted in a decrease in oceanic pH. In this study, we assessed the natural variability of pH in coastal waters off Goa, eastern Arabian Sea. pH_T showed large variability (7.6–8.1) with low pH conditions during south‐west monsoon (SWM), and the variability is found to be associated with upwelling rather than freshwater runoff. Considering that marine biota inhabiting dynamic coastal waters off Goa are exposed to such wide range of natural fluctuations of pH, an acidification experiment was carried out. We studied the impact of low pH on the local population of sea urchin Stomopneustes variolaris (Lamarck, 1816). Sea urchins were exposed for 210 days to three treatments of pH_T: 7.96, 7.76 and 7.46. Our results showed that S. variolaris at pH_T 7.96 and 7.76 were not affected, whereas the ones at pH_T 7.46 showed adverse effects after 120 days and 50% mortality by 210 days. However, even after exposure to low pH for 210 days, 50% organisms survived. Under low pH conditions (pH_T 7.46), the elemental composition of sea urchin spines exhibited deposition of excess Sr²⁺ as compared to Mg²⁺ ions. We conclude that although the sea urchins would be affected in future high CO₂ waters, at present they are not at risk even during the south‐west monsoon when low pH waters reside on the shelf.

中文翻译：

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果阿（东阿拉伯海）附近的pH值变化以及海胆对海洋酸化情景的响应

在过去的几十年中，大气中CO ₂浓度的增加导致海洋pH值降低。在这项研究中，我们评估了阿拉伯海东部果阿附近沿海水域pH值的自然变化。在西南季风（SWM）的低pH条件下，pH _T表现出较大的变化（7.6–8.1），并且发现该变化与上升流有关，而不是与淡水径流有关。考虑到居住在果阿附近动态沿海水域的海洋生物区系受到pH值如此大范围的自然波动的影响，因此进行了酸化实验。我们研究了低pH值对当地海胆天蛾的种群的影响（Lamarck，1816年）。将海胆暴露于pH值的三种处理下210天_T：7.96、7.76和7.46。我们的结果表明，在pH _T 7.96和7.76的天花链霉菌不受影响，而在pH _T 7.46的天花链霉菌在120天后显示出不良反应，到210天时显示出50％的死亡率。但是，即使在低pH值下暴露210天后，仍有50％的生物存活。在低pH条件（pH _T 7.46）下，海胆棘刺的元素组成与Mg ²⁺离子相比沉积了过量的Sr ²⁺。我们得出的结论是，尽管海胆会在未来的高CO ₂水中受到影响，但即使在西南季风期间低pH的水留在架子上，目前它们也没有受到威胁。