Benthic macroinvertebrates and selected physico-chemical parameters in two tributaries of the Wekiva River, Central Florida, USA

Abstract

Benthic macroinvertebrate densities and selected physico-chemical parameters of two tributaries of the Wekiva River, central Florida, USA, were investigated monthly for two years. Thirty major taxa were enumerated, and 54 organisms identified to genus and/or species. Mean macroinvertebrate density in Blackwater Creek was 843 organisms/m^2 and 1,272 organisms/m^2 in Rock Springs Run. Family Chironomidae (Diptera) numerically dominated the benthos of the streams, comprising 40.9% (Blackwater Creek) and 34.8% (Rock Springs Run) of the total macroinvertebrates collected. This was followed by total Ephemeroptera (14.5%), total Annelida (11.7%), Amphipoda (7.0%) and total Mollusca (5.8%) in Blackwater Creek; total Mollusca (26.9%), total Annelida (12.5%), total Ephemeroptera (7.5%) and Amphipoda (7.2%) in Rock Springs Run. Blackwater Creek supported significantly (P<0.05) more Isopoda, Hydropsychidae and total Trichoptera than Rock Springs Run, while the latter supported significantly more total invertebrates, total Annelida, Oligochaeta, total Mollusca, Gastropoda, and Pelecypoda. Significant correlations found for both streams between invertebrate densities and water parameters were : Oligochaeta with current velocity (P<0.0001,γ=0.68,n=45) and Nematoda with dissolved oxygen (P=0.0006,γ=0.48,n=48). Mean Hilsenhoff water quality biotic index values were 6.17 for Blackwater Creek and 5.96 for Rock Springs Run, indicating good-fair water quality in these systems.