Experimental support for alternative attractors on coral reefs
Experimental support for alternative attractors on coral reefs
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DOI：
10.1073/pnas.1812412116
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发表时间：
2019-02-11
影响因子：
11.1
通讯作者：
Adam TC
中科院分区：
文献类型：
--
作者：
Schmitt RJ;Holbrook SJ;Davis SL;Brooks AJ;Adam TC
生态学理论预测，在相同的环境条件下，一个生态系统可以有一个以上的社区状态，通过加强反馈来维持。如果是这样的话，一个足够大的干扰可以将系统翻转到一个难以逆转的不太理想的社区。在这里，我们证明了珊瑚礁可以被困在海藻占主导地位的状态下，在相同的条件下，珊瑚茁壮成长。其影响是深远的，特别是考虑到世界各地的珊瑚礁越来越多地转向海藻。我们的研究结果表明，预期的管理策略，减少切换到海藻的机会将比那些旨在恢复珊瑚群落后的转变更有效。生态学理论预测，具有多个吸引流域的生态系统可能会被锁定在一个不希望的状态，这具有深刻的生态和管理意义。尽管它们的重要性，替代吸引子已被证明是具有挑战性的检测和自然社区的特点。在珊瑚礁方面，有人假设，草食动物的过度捕捞和/或营养物富集可能导致珊瑚持续向大型藻类“相移”，这可能反映了向替代吸引物的状态转变，但迄今为止，证据一直不明确。我们在莫雷阿，法属波利尼西亚的实地实验，揭示了以下几点：（一）滞后存在于草食动物的大型藻类的关系，创造了潜在的珊瑚，大型藻类的双稳态在某些水平的草食动物，和（二）大型藻类是一个替代的吸引人在泻湖的现行条件下，但不是在前礁，环境草食动物落在实验划定的滞后区域之外。这些发现有助于解释在过去几十年里，莫雷阿环礁泻湖和前礁栖息地之间的干扰所引起的不同社区反应，并加强了这样一种观点，即扭转珊瑚礁上不受欢迎的转变可能很困难。我们的实验框架代表了一个强大的诊断工具，以探测生态系统中的多个吸引子，因此，可以告知在不断升级的压力面前维持关键生态系统功能所需的管理策略。
Ecological theory predicts that under the same environmental conditions, an ecosystem could have more than one community state that is maintained by reinforcing feedbacks. If so, a sufficiently large disturbance can flip the system to a less desired community that is difficult to reverse. Here, we demonstrate that a coral reef can become trapped in a seaweed-dominated state in the same conditions under which corals thrive. The implications are profound, particularly in light of the increasing occurrence of shifts to seaweed on coral reefs worldwide. Our results indicate that anticipatory management strategies that lessen the chance of a switch to seaweeds will be more effective than those aimed at restoring the coral community after a shift. Ecological theory predicts that ecosystems with multiple basins of attraction can get locked in an undesired state, which has profound ecological and management implications. Despite their significance, alternative attractors have proven to be challenging to detect and characterize in natural communities. On coral reefs, it has been hypothesized that persistent coral-to-macroalgae “phase shifts” that can result from overfishing of herbivores and/or nutrient enrichment may reflect a regime shift to an alternate attractor, but, to date, the evidence has been equivocal. Our field experiments in Moorea, French Polynesia, revealed the following: (i) hysteresis existed in the herbivory–macroalgae relationship, creating the potential for coral–macroalgae bistability at some levels of herbivory, and (ii) macroalgae were an alternative attractor under prevailing conditions in the lagoon but not on the fore reef, where ambient herbivory fell outside the experimentally delineated region of hysteresis. These findings help explain the different community responses to disturbances between lagoon and fore reef habitats of Moorea over the past several decades and reinforce the idea that reversing an undesired shift on coral reefs can be difficult. Our experimental framework represents a powerful diagnostic tool to probe for multiple attractors in ecological systems and, as such, can inform management strategies needed to maintain critical ecosystem functions in the face of escalating stresses.
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