Looking at the soft-bottom around a coastal coral reef: the impact of terrigenous input on Polychaeta (Annelida) community

ABSTRACT Erosion on coral reefs produces fragments of the constructor organisms that are scattered all around, thus enlarging the reef boundaries. Statistical modelling approach was used to investigate whether the Polychaeta community around Sebastião Gomes reef (Abrolhos Bank, Brazil) is influenced equally by sediment characteristics and/or by position related to the reef, that are variables related to the terrigenous input influence. In July 2007, a period dominated by winds that resuspend fine sediment from the land to coastal reefs, sediment samples were taken on four transects perpendicular to the reef (S, W, N and E) and a total of 121 species of polychaetes were recorded. The most abundant species was the carnivorous Goniadides carolinae and the model selected for it approximates to the best models fitted for both total macrofauna and polychaete abundance. These models represented higher abundance in coarse carbonate sediments on windward reef faces, where there is almost no terrigenous sediment. On the other hand, the Polychaeta richness did not depend on the transects. Sebastião Gomes reef is one of the many coastal reefs from Abrolhos Bank, whose healthy is probably in danger because of the increase of mud related to human activities, as deforestation and, recently, mining waste.

珊瑚礁侵蚀会产生造礁生物的碎片，这些碎片四散分布，进而扩大珊瑚礁的边界。本研究采用统计建模方法，探究巴西阿布洛霍斯海台（Abrolhos Bank）塞巴斯蒂昂戈麦斯礁（Sebastião Gomes Reef）周边的多毛纲（Polychaeta）群落，是否同等地受沉积物特征以及与礁体相关的位置（二者均为与陆源输入影响相关的变量）的调控。2007年7月，此时的主导风向为将陆源细沉积物（terrigenous sediment）吹送至沿岸珊瑚礁的风向，研究人员在4条垂直于礁体的样带（南S、西W、北N、东E）采集了沉积物样本，共记录到121种多毛纲动物。丰度最高的物种为肉食性的Goniadides carolinae，针对该物种筛选出的最优模型，与适配总大型底栖动物（macrofauna）及多毛纲动物丰度的最优模型拟合效果相近。上述模型显示，在几乎无陆源沉积物的礁体迎风面粗粒碳酸盐沉积物中，多毛纲动物丰度更高。另一方面，多毛纲物种丰富度则与样带位置无关。塞巴斯蒂昂戈麦斯礁是阿布洛霍斯海台众多沿岸珊瑚礁之一，其生态健康或因森林砍伐、近期采矿废弃物等人类活动带来的泥质沉积物增加而面临威胁。