We compared 15 blackwater and clearwater streams in coastal drainages of Alabama by quantifying fish assemblages and associated environmental conditions across multiple seasons and characterizing potential relationships using multivariate statistical approaches. Clearwater stream channels tended to be deeper, to have sandier substrates, and to have higher dissolved oxygen concentrations than blackwater streams. In contrast, blackwater streams showed higher dissolved organic carbon levels and higher benthic macroinvertebrate densities. Discriminant function analysis based on environmental and invertebrate data resulted in 90% discrimination between the two stream types. Nonmetric multidimensional scaling (NMDS) of seasonal fish assemblages indicated separation by stream type, with no overlap in fish assemblages of blackwater and clearwater streams in any season, and 12 (39%) of the 31 species captured were indicative of stream type. A suite of environmental and biological variables representing invertebrate density, discharge, stream size, water chemistry, and land use was correlated with NMDS axes separating fish assemblages by stream type. Fish traits were somewhat distinctive between stream types, as there were unique lie‐in‐wait predators and short‐lived species in each stream type. A fourth‐corner analysis indicated potential linkages between fishes preferring woody substrate and stream type, further suggesting that stream type may explain fish functional structure. These results emphasize the need to consider these coastal systems as biotically unique ecosystem types in conservation plans as well as to focus more attention on better understanding the diversity patterns in headwater streams within the Coastal Plains region.

中文翻译：

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黑水和清水溪流中的环境和鱼类聚集对比

我们通过量化多个季节的鱼类聚集和相关环境条件，并使用多元统计方法表征潜在关系，比较了阿拉巴马州沿海排水区的15条黑水和清水流。清水河道比黑水河道更深，底物更沙，溶解氧浓度更高。相反，黑水流显示出较高的溶解有机碳含量和较高的底栖大型无脊椎动物密度。基于环境和无脊椎动物数据的判别函数分析导致两种流类型之间的区分率为90％。季节性鱼类组合的非度量多维标度（NMDS）表示按流类型进行了分离，在任何季节，黑水流和清水流的鱼类组合都没有重叠，并且在捕获的31个物种中有12种（39％）指示了水流类型。代表无脊椎动物密度，流量，水流大小，水化学和土地利用的一系列环境和生物变量与按流类型将鱼群分开的NMDS轴相关。溪流类型之间的鱼类特征有些不同，因为每种溪流类型都有独特的等待捕食者和短命物种。第四角分析表明，喜欢木质底物的鱼与溪流类型之间存在潜在的联系，进一步表明溪流类型可以解释鱼的功能结构。