Data from: Episodic disturbance from boat anchoring is a major contributor to, but does not alter the trajectory of, long-term coral reef decline

Isolating the relative effects of episodic disturbances and chronic stressors on long-term community change is challenging. We assessed the impact of an episodic disturbance associated with human visitation (boat anchoring) relative to other drivers of long-term change on coral reefs. A one-time anchoring event at Crab Cove, British Virgin Islands, in 2004 caused rapid losses of coral and reef structural complexity that were equal to the cumulative decline over 23 years observed at an adjacent site. The abundance of small site-attached reef fishes dropped by approximately one quarter after the anchoring event, but this drop was not immediate and only fully apparent two years after the anchoring event. There was no obvious recovery from the impact, and no evidence that this episodic impact accelerated or retarded subsequent declines from other causes. This apparent lack of synergism between the effect of this episodic human impact and other chronic stressors is consistent with the few other long-term studies of episodic impacts, and suggests that action to mitigate anchor damage should yield predictable benefits.

厘清短期扰动（episodic disturbance）与慢性胁迫因子（chronic stressor）对群落长期变化的相对效应，是一项极具挑战性的研究工作。本研究以珊瑚礁生态系统为对象，针对与人类活动相关的短期扰动——船舶抛锚（boat anchoring），结合驱动珊瑚礁长期变化的其他因子，评估了该扰动的影响效应。2004年发生于英属维尔京群岛蟹湾（Crab Cove）的单次抛锚事件，造成了珊瑚与礁体结构复杂度的快速损失，其幅度等同于邻近观测站点23年间的累积退化程度。该抛锚事件发生后，定居性小型礁栖鱼类（site-attached reef fishes）的丰度下降约四分之一，但该下降并非即时发生，仅在事件发生两年后才完全显现。此次扰动未出现明显的生态恢复迹象，且无证据表明该短期扰动会加剧或缓解由其他因素引发的后续群落退化。本次人类活动短期扰动与其他慢性胁迫因子之间未表现出明显的协同效应，这一结果与现有少量短期扰动长期监测研究的结论一致，同时也表明，采取措施减轻船舶抛锚造成的礁体损伤，可带来可预期的生态效益。