Evidence for and against the existence of alternate attractors on coral reefs
Evidence for and against the existence of alternate attractors on coral reefs
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DOI：
10.1111/j.1600-0706.2012.00262.x
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发表时间：
2013-04-01
期刊：
影响因子：
3.4
通讯作者：
Hastings, Alan
中科院分区：
文献类型：
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作者：
Mumby, Peter J.;Steneck, Robert S.;Hastings, Alan
综合珊瑚礁被广泛认为表现出多种吸引力，这对依赖它们的人有深远的影响。如果珊瑚礁被困在一个由海藻主导的自我强化状态中，管理者将系统重新转变为自然的、多产的珊瑚状态将变得不成比例地困难和昂贵。多个吸引子的存在是有争议的。我们评估了各种形式的证据，并得出结论，仍然没有确凿的证据，多个吸引珊瑚礁。然而，最令人信服的证据，结合生态模型和现场数据，是更符合多个吸引比竞争的假设，只有一个单一的，珊瑚吸引。管理人员应谨慎行事，并假设退化的珊瑚礁可能会被困在那里。在具有缓慢动态和频繁脉冲扰动的生态系统中，测试交替吸引子的存在是非常具有挑战性的。珊瑚礁是这种情况的典型，交替吸引子的存在是有争议的。我们分析了不同形式的证据，并评估它们是否支持或挑战加勒比海珊瑚礁上存在的多种吸引物，其中许多已经显示出从珊瑚到藻类主导的群落结构的深刻相变。实地研究本身没有提供深入了解多个吸引子，因为珊瑚礁动态的非平衡性质，防止被观察到的平衡。统计模型有可能无法对出现多个吸引子的参数空间进行采样，也无法考虑异质环境、人为驱动因素（如捕鱼）和重大干扰（如飓风）的混杂效应。简单和复杂的模型都在系统驱动程序的某些区域（但不是所有区域）上找到多个吸引子（钓鱼）。用现场数据对模型预测进行的检验与交替吸引子理论密切匹配，但只有一个吸引子的前倾单调曲线也可以拟合到这些数据。深入考虑这种单调关系的假设揭示了重要的生态问题，消失在一个模型的多个吸引。迄今为止，没有证据表明加勒比海珊瑚礁上存在多个吸引物，虽然仍然没有确切的证据，但证据和生态推理的平衡有利于它们的存在。理论预测，加勒比海的珊瑚礁在自然状态下不会表现出交替的吸引子，但疾病引起的两个关键功能群的丧失产生了双稳态。交替吸引物是成为珊瑚礁动态的一个持久因素，还是成为其地质历史中的一个短暂时刻，将部分取决于功能群的恢复能力以及气候变化和海洋酸化对珊瑚生长和死亡的影响。
Synthesis Coral reefs are widely thought to exhibit multiple attractors which have profound implications for people that depend on them. If reefs become stuck' within a self-reinforcing state dominated by seaweed, it becomes disproportionately difficult and expensive for managers to shift the system back towards its natural, productive, coral state. The existence of multiple attractors is controversial. We assess various forms of evidence and conclude that there remains no incontrovertible proof of multiple attractors on reefs. However, the most compelling evidence, which combines ecological models and field data, is far more consistent with multiple attractors than the competing hypothesis of only a single, coral attractor. Managers should exercise caution and assume that degraded reefs can become stuck there. Testing for the existence of alternate attractors in ecosystems that possess slow dynamics and frequent pulse perturbation is exceptionally challenging. Coral reefs typify such conditions and the existence of alternate attractors is controversial. We analyse different forms of evidence and assess whether they support or challenge the existence of multiple attractors on Caribbean reefs, many of which have shown profound phase shifts in community structure from coral to algal dominance. Field studies alone provide no insight into multiple attractors because the non-equilibrial nature of reef dynamics prevents equilibria from being observed. Statistical models risk failing to sample the parameter space in which multiple attractors occur, and have failed to account for the confounding effects of heterogeneous environments, anthropogenic drivers (e.g. fishing), and major disturbances (e.g. hurricanes). Simple and complex models all find multiple attractors over some though not all regions of a system driver (fishing). Tests of model predictions with field data closely match theory of alternate attractors but a forward-leaning monotonic curve with only a single attractor can also be fitted to these data. Deeper consideration of the assumptions of this monotonic relationship reveal significant ecological problems which disappear under a model of multiple attractors. To date, there is no evidence against the existence of multiple attractors on Caribbean reefs and while there remains no definitive proof, the balance of evidence and ecological reasoning favours their existence. Theory predicts that Caribbean reefs do not exhibit alternate attractors in their natural state but that disease-induced loss of two key functional groups has generated bistability. Whether alternate attractors becomes a persistent element of reef dynamics or a brief moment in their geological history will depend, in part, on the ability of functional groups to recover and the impacts of climate change and ocean acidification on coral growth and mortality.