Fish Assemblage Structure and Habitat Associations in Blackwater Streams and Wetlands of Alabama’s Southern Pine Plains and Hills

Abstract

Fish community structure in headwater streams and wetlands of the Southern Pine Plains and Hills (SPPH) was primarily determined by landscape-scale differences in water chemistry, aligning with broad divisions in geology. This study provides evidence that water chemistry is a dominant driver of stream fish communities in the SPPH. Streams passing over carbonate geology had highly distinct communities compared to streams restricted to non-carbonate sand geology. Total dissolved solids (TDS), conductivity, and dissolved oxygen (DO) emerged as overarching drivers of fish community structure. Minimum pH was identified as a dominant signal of species richness, explaining approximately 50% of variation. Many important water chemistry measures did not align with contemporary blackwater definitions, particularly at finer spatial scales. Water color and concentration of dissolved organic carbon did not explain any significant proportion of fish community variation. Additionally, headwater wetland fish communities were identified as robust, perennial, and significantly distinct from adjacent stream communities. No effect of season on fish community structure was detected.