Instituto de Ciências Do Mar (LABOMAR), Universidade Federal Do Ceará (UFC), Fortaleza, Brazil.
Universidade Federal Do Delta Do Parnaíba (UFDPAr), Parnaíba, Brazil.
Sci Rep. 2024 Nov 28;14(1):29607. doi: 10.1038/s41598-024-76641-1.
The low-latitude habitats of the South American reef system have a high endemism and represent important stepping-stones due to the connectivity with Amazon and Caribbean reefs. We provide the first seabed mapping, and analyze the benthic cover and fish assemblages of these extreme reefs. Fleshy macroalgae (2-66% of cover), algal turfs (0-47%), and sponges (3-25%) are the dominant benthic groups. The main reef builders are crustose coralline algae (2-23%) and only four coral species (0 to 18%), mainly the weedy Siderastrea stellata. Cluster analysis distinguished two groups. The first group includes the shallowest reefs (~ 17 m deep) where fleshy macroalgae are abundant together with higher siltation on the reefs (~ 31% covered by sediments). The second group, by contrast, includes the deeper reefs (22.5-27 m), which have much higher algal turf cover, and the lowest sediment cover (4%). The deeper reefs also have the highest cover of corals (18%) and sponges (25%). We recorded a total of 63 fish species, with the deep reefs being the richest. Analysis indicated that the composition of the benthos was considerably more homogeneous across the study area than the composition of fish assemblages, which had a higher turnover of species among reefs. Moreover, we identified the depth of the reef as a variable structuring the benthic assemblages. The fish assemblage is influenced, in turn, by the benthos. Overall, the seabed mapping revealed the existence of a single reef system with high spatial heterogeneity. Our results provide new insights into the structure of these extreme reefs that have evolved under the influence of sediment resuspension, moderate turbidity, and are warmer than other West Atlantic reefs located at middle- and high-latitudes.
南美珊瑚礁系统的低纬度生境具有很高的特有性，并且由于与亚马逊和加勒比海珊瑚礁的连通性，它们是重要的踏脚石。我们提供了首次海底测绘，并分析了这些极端珊瑚礁的底栖覆盖物和鱼类群落。肉质大型藻类（占覆盖面积的 2-66%）、藻坪（0-47%）和海绵（3-25%）是主要的底栖生物群。主要的珊瑚礁建造者是壳状珊瑚藻（2-23%），只有四种珊瑚物种（0 到 18%），主要是杂草丛生的星珊瑚。聚类分析将这两个群体区分开来。第一组包括最浅的珊瑚礁（17 米深），那里肉质大型藻类丰富，同时珊瑚礁上有更多的泥沙淤积（31%被沉积物覆盖）。相比之下，第二组包括更深的珊瑚礁（22.5-27 米），那里的藻坪覆盖率更高，沉积物覆盖率最低（4%）。更深的珊瑚礁也有最高的珊瑚（18%）和海绵（25%）覆盖率。我们总共记录了 63 种鱼类，其中深礁的种类最丰富。分析表明，与鱼类群落的组成相比，研究区域内底栖生物的组成要均匀得多，而鱼类群落之间的物种更替更为频繁。此外，我们发现珊瑚礁的深度是一个结构底栖生物群落的变量。反过来，鱼类群落也受到底栖生物的影响。总的来说，海底测绘揭示了存在一个具有高度空间异质性的单一珊瑚礁系统。我们的研究结果为这些在泥沙再悬浮、中等浑浊度和比位于中高纬度的其他西大西洋珊瑚礁更温暖的条件下演化而来的极端珊瑚礁的结构提供了新的见解。
