Departamento de Oceanografia, Universidade Federal de Pernambuco, Recife, PE, 50670-901, Brazil.
Institut de Recherche pour le Développement, MARBEC, Université Montpellier, CNRS, IFREMER, IRD, 34200, Sète, France.
Sci Rep. 2022 Jan 11;12(1):537. doi: 10.1038/s41598-021-04165-z.
The dispersal of marine organisms can be restricted by a set of isolation mechanisms including hard barriers or hydrological features. In the Western Atlantic Ocean, the Amazon River discharge has been shown to act as a biogeographical barrier responsible for the differences in reef fish communities between Caribbean Sea and Northeast Brazil continental shelves. Here, we compare the diversity of all Animalia phyla from biogeographic ecoregions along the Tropical Western Atlantic continental shelf to test the hypothesis that the Amazon River plume spatially structures species diversity. For that, we used beta diversity estimators and multivariate ecological analysis on a database of species occurrence of the whole animal kingdom including 175,477 occurrences of 8,375 species from six ecoregions along the Western Tropical Atlantic. Results of the whole animal kingdom and the richest phyla showed that the Caribbean Sea and Tropical Brazil ecoregions are isolated by the Amazon River Plume, broadening and confirming the hypothesis that it acts as a soft barrier to animal dispersal in the Western Tropical Atlantic. Species sharing is larger northwestwards, in direction of the Caribbean than the opposite direction. Beyond species isolation due to local characteristics such as low salinity and high turbidity, our results suggest the dominant northwestward currents probably play a major role in animal dispersion: it enhances the flux of larvae and other planktonic organisms with reduced mobility from Brazil to Caribbean and hinders their contrary movement. Thus, the Amazon area is a strong barrier for taxa with reduced dispersal capacity, while species of pelagic taxa with active swimming may transpose it more easily.
海洋生物的扩散可能受到一系列隔离机制的限制，包括硬障碍或水文学特征。在西大西洋，亚马逊河的流量已被证明是一种生物地理屏障，导致加勒比海和东北巴西大陆架之间的珊瑚鱼群落存在差异。在这里，我们比较了热带西大西洋大陆架沿线生物地理生态区所有动物门的多样性，以检验亚马逊河羽流在空间上构建物种多样性的假设。为此，我们使用了 beta 多样性估计值和多元生态分析，对包括来自西热带大西洋六个生态区的 8,375 个物种的 175,477 个物种出现的数据库进行了分析。整个动物王国和最丰富的门的结果表明，加勒比海和热带巴西生态区被亚马逊河羽流隔开，从而扩大并证实了它在西热带大西洋作为动物扩散的软屏障的假设。在方向上，加勒比方向的物种共享比相反方向更大。除了由于低盐度和高浊度等局部特征导致的物种隔离外，我们的结果还表明，主导的西北向海流可能在动物扩散中发挥主要作用：它增强了从巴西到加勒比的幼虫和其他浮游生物的通量，而减少了它们的反向运动。因此，亚马逊地区是扩散能力较弱的分类群的强大屏障，而具有主动游动能力的浮游生物类群的物种可能更容易穿越它。
