Seagrass habitats at the Cocos (Keeling) Islands (CKI), a remote atoll in the Indian Ocean, have suffered a catastrophic decline over the last decade. Seagrass monitoring (1996–2020) in relation to dredging and coastal development works (2009 to 2011) provide a historical baseline, and document the decline of mixed tropical seagrass Thalassia hemprichii and macroalgal (predominantly Caulerpa spp.) beds over a decadal scale time series. Attribution of loss to coastal development is confounded by lagoon-wide die-off events in 2007, 2009 and 2012 and high air and water temperatures from 2009 to 2016, with evidence of broad scale changes, visible in satellite imagery between 2006 and 2018. We conclude that up to 80% of seagrass habitats in the CKI lagoon (~1200 ha) have been lost due to multiple stressors including episodic die-off events related to high temperatures and calm conditions, and loss due to sediment disturbance and increased turbidity. Grazing pressure from the resident green sea turtles (Chelonia mydas) may have also exacerbated the loss of seagrass, which in turn poses a dire threat to their ongoing health and survival. This study highlights the fragility of tropical seagrass habitats and the cascading effect of system imbalance as a result of anthropogenic pressures and climate drivers. Although small in comparison to global estimates, the loss of seagrass habitats at CKI could change the entire ecosystem of a remote atoll. Due to the significance of the Thalassia beds for coastal stability, as food for an isolated population of green sea turtles and as a fish nursery, rehabilitation efforts are warranted.

印度洋偏远环礁科科斯（基林）群岛（CKI）的海草栖息地在过去十年中遭受了灾难性的减少。与疏浚和沿海开发工程（2009 年至 2011 年）相关的海草监测（1996 年至 2020 年）提供了历史基线，并记录了混合热带海草Thalassia hemprichii和大型藻类（主要是Caulerpa spp.）床在十年尺度时间序列中的衰退情况。沿海开发造成的损失与 2007 年、2009 年和 2012 年的泻湖范围内的死亡事件以及 2009 年至 2016 年的高气温和水温相混淆，并有证据表明 2006 年至 2018 年期间卫星图像中可见大规模变化。结论是，CKI 泻湖（约 1200 公顷）中高达 80% 的海草栖息地因多种压力因素而消失，包括与高温和平静条件相关的偶发性死亡事件，以及由于沉积物扰动和浑浊度增加而造成的损失。来自当地绿海龟（Chelonia mydas）的吃草压力也可能加剧了海草的损失，这反过来又对它们的持续健康和生存构成了可怕的威胁。这项研究强调了热带海草栖息地的脆弱性以及人为压力和气候驱动因素导致的系统失衡的连锁效应。尽管与全球估计相比规模较小，但 CKI 海草栖息地的丧失可能会改变偏远环礁的整个生态系统。由于地中海海床对沿海稳定的重要性、作为孤立的绿海龟种群的食物和鱼类育苗地，因此有必要进行恢复工作。