Allen Katherine A, Bruno John F, Chong Fiona, Clancy Damian, McClanahan Tim R, Spencer Matthew, Żychaluk Kamila
School of Environmental Sciences, University of Liverpool, Liverpool, United Kingdom.
Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
PeerJ. 2017 May 17;5:e3290. doi: 10.7717/peerj.3290. eCollection 2017.
Coral reefs are dynamic systems whose composition is highly influenced by unpredictable biotic and abiotic factors. Understanding the spatial scale at which long-term predictions of reef composition can be made will be crucial for guiding conservation efforts. Using a 22-year time series of benthic composition data from 20 reefs on the Kenyan and Tanzanian coast, we developed Bayesian vector autoregressive state-space models for reef dynamics, incorporating among-site variability, and quantified their long-term behaviour. We estimated that if there were no among-site variability, the total long-term variability would be approximately one-third of its current value. Thus, our results showed that among-site variability contributes more to long-term variability in reef composition than does temporal variability. Individual sites were more predictable than previously thought, and predictions based on current snapshots are informative about long-term properties. Our approach allowed us to identify a subset of possible climate refugia sites with high conservation value, where the long-term probability of coral cover ≤0.1 (as a proportion of benthic cover of hard substrate) was very low. Analytical results show that this probability is most strongly influenced by among-site variability and by interactions among benthic components within sites. These findings suggest that conservation initiatives might be successful at the site scale as well as the regional scale.
珊瑚礁是动态系统，其组成受到不可预测的生物和非生物因素的高度影响。了解能够对珊瑚礁组成进行长期预测的空间尺度，对于指导保护工作至关重要。利用来自肯尼亚和坦桑尼亚海岸20个珊瑚礁的22年底栖生物组成数据时间序列，我们开发了用于珊瑚礁动态的贝叶斯向量自回归状态空间模型，纳入了站点间变异性，并量化了它们的长期行为。我们估计，如果不存在站点间变异性，总长期变异性将约为其当前值的三分之一。因此，我们的结果表明，站点间变异性对珊瑚礁组成长期变异性的贡献大于时间变异性。单个站点比之前认为的更具可预测性，基于当前快照的预测对于长期特性具有参考价值。我们的方法使我们能够识别出具有高保护价值的可能的气候避难所站点子集，在这些地方，珊瑚覆盖率≤0.1（占硬底质底栖生物覆盖率的比例）的长期概率非常低。分析结果表明，这种概率受站点间变异性以及站点内底栖生物成分之间相互作用的影响最大。这些发现表明，保护举措在站点尺度和区域尺度上都可能取得成功。
