Marked alterations of aquatic habitats can have profound consequences for the abundances and distributional patterns of associated faunal organisms. Recognition of this fact has motivated multiple state and federal agency initiatives related to habitat management, and encouraged a mechanistic understanding of plant animal relationships vital for assessing ecological change. We assessed linkages between specific aquatic habitat types (submerged aquatic vegetation, SAV) and small bodied fish and macroinvertebrates (SFI) in the Homosassa and Chassahowitzka rivers; spring-fed rivers along the west coast of peninsular Florida. A decade of research indicates a shift in the SAV communities within each of these systems, with decreases in rooted macrophytes (e.g., Vallisneria americana and Sagittaria kurziana) and concomitant increases in the relative abundance of nuisance filamentous macroalgae. To assess how these shifts in SAV might affect the SFI community we: 1) determined if the SFI community differed between specific types of SAV habitat, and 2) analyzed a suit of response variables to investigate the mechanisms that might underlie observed differences. We sampled SFI associated with five SAV habitat types and used monthly mapping of habitats to estimate quantitatively the occurrence of specific SAV habitat types. 

Results/Conclusions

Our results suggest that both SFI density and species composition were significantly related to SAV habitat type. Contrary to common perception, SFI densities were generally highest in filamentous macroalgae. However, Shannon’s diversity index values were lowest for SFI occupying filamentous macroalgae and higher for SFI occupying native rooted macrophytes. Additionally, we found significant differences in size distributions of common species (e.g., Lucania parva) between SAV types, with larger individuals associated with rooted macrophytes. These findings, in combination with the available longer-term monitoring data, provide insight into how continued shifts in SAV may affect the structure and function of Florida’s spring-fed rivers and other aquatic ecosystems. This information is essential for understanding how habitat-animal relationships impact the ecology of an ecosystem undergoing wide-scale habitat change, and may be useful to managers as a decision support tool.