The Western Indian Continental Shelf (WICS) experiences upwelling during the Southwest Monsoon (SWM), leading to deoxygenation and acidification of subsurface waters. The region has patchy growth of corals, e.g. in the Grande Island and Angria Bank. Measurements made during the late SWM of 2022 reveal that the shelf waters around the Grande Island were subject to varying environmental conditions, viz. lower temperature (21.3–26.1°C), oxygen (0–4.9 mL L) and pH (7.506–7.927). Complete anoxia was associated with sulphide build-up to a maximum of 5.9 μmol L at 17 m depth. An additional episodic condition (high temperature, low oxygen and pH) also occurred associated presumably with a plankton bloom in April 2017. Hence, unlike the offshore coral site Angria Bank, waters around the Grande Island experiences extreme changes in physico-chemical conditions (e.g. Ω ∼1.2–1.8 during October 2022) seasonally as reported here. The biogeochemical conditions are however not as intense (Ω = 0.6) as observed along the eastern boundary upwelling system of the Pacific Ocean.

中文翻译：

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印度中西海岸珊瑚栖息地周围季节性变化的生物地球化学状况

西印度大陆架 (WICS) 在西南季风 (SWM) 期间经历上升流，导致地下水脱氧和酸化。该地区有零散的珊瑚生长，例如格兰德岛和安格里亚浅滩。 2022 年末 SWM 期间进行的测量表明，格兰德岛周围的陆架水域受到不同的环境条件的影响，即。较低的温度 (21.3–26.1°C)、氧气 (0–4.9 mL L) 和 pH (7.506–7.927)。完全缺氧与 17 m 深度处硫化物累积量最高可达 5.9 μmol·L 相关。另一种突发状况（高温、低氧和 pH 值）也发生了，推测与 2017 年 4 月的浮游生物大量繁殖有关。因此，与近海珊瑚礁安格里亚浅滩不同，格兰德岛周围的水域经历了物理化学条件的极端变化（例如2022 年 10 月期间 Ω ∼1.2–1.8) 季节性，如此处报道。然而，生物地球化学条件并不像沿太平洋东部边界上升流系统观察到的那样强烈（Ω = 0.6）。