ABSTRACT Molluscs are an important component of the macrofauna at coastal lagoons and a relevant invertebrate group used as an ecological indicator of environmental impacts on these ecosystems. In this study, we used a multivariate approach to assess spatial distribution changes of molluscan assemblages along a salinity gradient in four habitats from a tropical coastal lagoon. Throughout 1 year, we collected samples at six sites in four identified habitats: i) muddy bottom near a fringing mangrove (MAN), ii) mangrove (Avicennia germinans) roots (RAI), iii) sandy-muddy bottom (ARE) and iv) submerged aquatic vegetation (VAS). We identified 29 molluscs species. The gastropods Neritina virginea and N. reclivata were the dominant species in the lagoon and bivalves Rangia flexuosa, Ischadium recurvum, and Crassostrea virginica occurred in all habitats and sites. Greater species richness was found during the rainy season and in the VAS habitat. Molluscan assemblages varied among seasons, habitats, and sites nested within habitats. Environmental variables that best explained seasonal molluscan assemblages were temperature and turbidity; along the lagoon, the best variables that explained molluscan assemblages were salinity and dissolved oxygen. This study supports the argument that preventing habitat loss or habitat conversion is an important issue to be considered for molluscan conservation at estuarine ecosystems.

中文翻译：

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软体动物在墨西哥湾沿海泻湖中沿盐度梯度的四个栖息地的分布

摘要 软体动物是沿海泻湖大型动物群的重要组成部分，也是相关的无脊椎动物群，被用作对这些生态系统的环境影响的生态指标。在这项研究中，我们使用多变量方法来评估来自热带沿海泻湖的四个栖息地中软体动物组合沿盐度梯度的空间分布变化。一年来，我们在四个已确定的栖息地的六个地点收集了样本：i) 边缘红树林 (MAN) 附近的泥泞底部，ii) 红树林 (Avicennia Germinans) 根 (RAI)，iii) 沙质泥泞底部 (ARE) 和 iv ) 沉水水生植被 (VAS)。我们确定了 29 种软体动物。腹足动物 Neritina virginea 和 N. reclivata 是泻湖中的优势种，双壳类动物 Rangia flexuosa、Ischadium recurvum、和 Crassostrea virginica 发生在所有栖息地和地点。在雨季和 VAS 栖息地发现了更大的物种丰富度。软体动物组合因季节、栖息地和栖息地内嵌套的地点而异。最能解释季节性软体动物组合的环境变量是温度和浊度；沿着泻湖，解释软体动物组合的最佳变量是盐度和溶解氧。本研究支持以下论点，即防止栖息地丧失或栖息地转变是河口生态系统软体动物保护需要考虑的重要问题。最能解释季节性软体动物组合的环境变量是温度和浊度；沿着泻湖，解释软体动物组合的最佳变量是盐度和溶解氧。本研究支持以下论点，即防止栖息地丧失或栖息地转变是河口生态系统软体动物保护需要考虑的重要问题。最能解释季节性软体动物组合的环境变量是温度和浊度；沿着泻湖，解释软体动物组合的最佳变量是盐度和溶解氧。本研究支持以下论点，即防止栖息地丧失或栖息地转变是河口生态系统软体动物保护需要考虑的重要问题。