Benthic and fish community composition as well as water quality along the Thousand Islands north of the megacity Jakarta, Indonesia

Worldwide, coral reefs are challenged by multiple stressors due to growing urbanization, industrialization and coastal development. Coral reefs along the Thousand Islands off Jakarta, one of the largest megacities worldwide, have degraded dramatically over recent decades. The shift and decline in coral cover and composition has been extensively studied with a focus on large-scale gradients (i.e. regional drivers), however special focus on local drivers in shaping spatial community composition is still lacking. Here, the spatial impact of anthropogenic stressors on local and regional scales on coral reefs north of Jakarta was investigated. Results indicate that the direct impact of Jakarta is mainly restricted to inshore reefs, separating reefs in Jakarta Bay from reefs along the Thousand Islands further north. A spatial patchwork of differentially degraded reefs is present along the islands as a result of localized anthropogenic effects rather than regional gradients. Pollution is the main anthropogenic stressor, with over 80 % of variation in benthic community composition driven by sedimentation rate, NO2, PO4 and Chlorophyll a. Thus, the spatial structure of reefs is directly related to intense anthropogenic pressure from local as well as regional sources. Therefore, improved spatial management that accounts for both local and regional stressors is needed for effective marine conservation.全球范围内，珊瑚礁正面临多重环境胁迫，其诱因包括日益加剧的城市化、工业化及沿海开发活动。雅加达作为全球特大城市之一，其外海的千岛群岛沿岸珊瑚礁在近数十年来出现了显著退化。此前针对珊瑚覆盖度与群落组成的变化及衰退现象，已有大量研究聚焦于大尺度环境梯度（即区域驱动因子），但针对塑造空间群落组成的局地驱动因子的专门研究仍较为匮乏。本研究针对雅加达以北海域的珊瑚礁系统，探究了人为胁迫因子在局地与区域尺度上的空间影响。研究结果表明，雅加达的直接影响主要局限于近岸礁体，将雅加达湾内的礁体与更北侧的千岛群岛沿岸礁体清晰分隔。群岛沿岸存在着一套呈现差异化退化程度的珊瑚礁空间镶嵌格局，其形成主要源于局地人为影响，而非区域环境梯度。污染是最主要的人为胁迫因子，底栖生物群落组成的变异中有超过80%由沉积速率、亚硝酸盐（NO₂）、磷酸盐（PO₄）及叶绿素a（Chlorophyll a）所驱动。综上，珊瑚礁的空间结构直接与来自局地及区域源的高强度人为压力密切相关。因此，若要开展高效的海洋保护工作，亟需建立兼顾局地与区域胁迫因子的精细化空间管理策略。