Clements Cody S, Hay Mark E
School of Biological Sciences, Georgia Institute of Technology, Atlanta, United States of America.
PLoS One. 2017 Feb 6;12(2):e0171569. doi: 10.1371/journal.pone.0171569. eCollection 2017.
The unanticipated impacts of consumers in fragmented habitats are frequently a challenge for ecosystem management. On Indo-Pacific coral reefs, crown-of-thorns sea stars (Acanthaster spp.) are coral predators whose outbreaks cause precipitous coral decline. Across large spatial scales, Acanthaster densities are lower in large no-take Marine Protected Areas (MPAs) and reefs subject to limited human exploitation. However, using a combination of observational and manipulative experiments, we found that Acanthaster densities within a network of small, no-take MPAs on reef flats in Fiji were ~2-3.4 times greater inside MPAs than in adjacent fished areas and ~2-2.5 times greater than the upper threshold density indicative of an outbreak. This appeared to result from selective Acanthaster migration to the coral-rich MPAs from fished areas that are coral-poor and dominated by macroalgae. Small MPAs can dramatically increase the cover of foundation species like corals, but may selectively attract coral predators like Acanthaster due to greater food densities within MPAs or because the MPAs are too small to support Acanthaster enemies. As coral cover increases, their chemical and visual cues may concentrate Acanthaster to outbreak densities that cause coral demise, compromising the value of small MPAs. An understanding of predator dynamics as a function of habitat type, size, and fragmentation needs to be incorporated into MPA design and management.
在破碎化栖息地中，消费者产生的意外影响常常给生态系统管理带来挑战。在印度-太平洋珊瑚礁上，棘冠海星（刺冠海星属）是珊瑚捕食者，其爆发会导致珊瑚急剧减少。在大空间尺度上，在大型禁捕海洋保护区（MPA）和受人类开发活动限制的珊瑚礁中，棘冠海星的密度较低。然而，通过观察性实验和操纵性实验相结合的方法，我们发现，在斐济礁坪上的小型禁捕MPA网络中，MPA内的棘冠海星密度比相邻的捕捞区域高出约2至3.4倍，比表明爆发的上限密度高出约2至2.5倍。这似乎是由于棘冠海星从珊瑚稀少且以大型藻类为主的捕捞区域选择性迁移到珊瑚丰富的MPA所致。小型MPA可以显著增加珊瑚等基础物种的覆盖面积，但由于MPA内食物密度更高，或者因为MPA太小无法支持棘冠海星的天敌，可能会选择性地吸引像棘冠海星这样的珊瑚捕食者。随着珊瑚覆盖面积的增加，它们的化学和视觉信号可能会使棘冠海星聚集到导致珊瑚死亡的爆发密度，从而损害小型MPA的价值。在MPA的设计和管理中，需要纳入对捕食者动态与栖息地类型、大小和破碎化之间关系的理解。
