Riegl Bernhard M, Sheppard Charles R C, Purkis Sam J
National Coral Reef Institute, Nova Southeastern University, Dania Beach, Florida, United States of America.
PLoS One. 2012;7(6):e36921. doi: 10.1371/journal.pone.0036921. Epub 2012 Jun 5.
We explore impacts on pristine atolls subjected to anthropogenic near-field (human habitation) and far-field (climate and environmental change) pressure. Using literature data of human impacts on reefs, we parameterize forecast models to evaluate trajectories in coral cover under impact scenarios that primarily act via recruitment and increased mortality of larger corals. From surveys across the Chagos, we investigate the regeneration dynamics of coral populations distant from human habitation after natural disturbances. Using a size-based mathematical model based on a time-series of coral community and population data from 1999-2006, we provide hind- and forecast data for coral population dynamics within lagoons and on ocean-facing reefs verified against monitoring from 1979-2009. Environmental data (currents, temperatures) were used for calibration. The coral community was simplified into growth typologies: branching and encrusting, arboresent and massive corals. Community patterns observed in the field were influenced by bleaching-related mortality, most notably in 1998. Survival had been highest in deep lagoonal settings, which suggests a refuge. Recruitment levels were higher in lagoons than on ocean-facing reefs. When adding stress by direct human pressure, climate and environmental change as increased disturbance frequency and modified recruitment and mortality levels (due to eutrophication, overfishing, pollution, heat, acidification, etc), models suggest steep declines in coral populations and loss of community diversification among habitats. We found it likely that degradation of lagoonal coral populations would impact regeneration potential of all coral populations, also on ocean-facing reefs, thus decreasing reef resilience on the entire atoll.
我们探讨了人为近场（人类居住）和远场（气候与环境变化）压力对原始环礁的影响。利用人类对珊瑚礁影响的文献数据，我们对预测模型进行参数化，以评估在主要通过大型珊瑚的补充和死亡率增加起作用的影响情景下珊瑚覆盖的变化轨迹。通过对查戈斯群岛的调查，我们研究了自然干扰后远离人类居住的珊瑚种群的恢复动态。基于1999 - 2006年珊瑚群落和种群数据的时间序列，使用基于大小的数学模型，我们提供了环礁湖内和面向海洋的珊瑚礁上珊瑚种群动态的历史和预测数据，并与1979 - 2009年的监测数据进行了验证。环境数据（洋流、温度）用于校准。珊瑚群落被简化为生长类型：分支状和覆盖状、树状和块状珊瑚。实地观察到的群落模式受到与白化相关的死亡率的影响，最显著的是在1998年。在深环礁湖环境中存活率最高，这表明存在避难所。环礁湖中的补充水平高于面向海洋的珊瑚礁。当通过直接的人类压力、气候和环境变化增加压力，如干扰频率增加以及补充和死亡率水平改变（由于富营养化、过度捕捞、污染、高温、酸化等）时，模型表明珊瑚种群将急剧下降，栖息地之间的群落多样性丧失。我们发现环礁湖珊瑚种群的退化很可能会影响所有珊瑚种群的恢复潜力，包括面向海洋的珊瑚礁上的种群，从而降低整个环礁的珊瑚礁恢复力。
