Spatio-temporal effects of selected physico-chemical variables of water, algae and sediment chemistry on the larval community of nuisance Chironomidae (Diptera) in a natural and a man-made lake in central Florida

Spatio-temporal distributions of Chironomus crassicaudatus, Chironomus decorus, Glyptotendipes paripes, Cryptochironomus fulvus and Tanypodinae midge larvae and selected associated environmental variables (physico-chemical variables of water, sediment chemistry and algal composition) were studied for one year in natural Lake Monroe and man-made Konomac Lake in central Florida. Ordination analysis (CCA with variation partitioning) showed that in each lake, sediment variables were the most important environmental variables. However, the most important proportion of species variability in pooled data from both lakes was explained by lake-specific combinations of water, sediment and algal variables. Chironomid larvae were ordinated with increasing depth as follows: G. paripes, C. fulvus, C. crassicaudatus, Tanypodinae, and C. decorus. This trend was similar for both lakes individually as well as for the pooled data. As water depth increased, organic matter content and associated metals concentrations in sediment increased. Glyptotendipes paripes displayed significant, negative correlation with water depth and sediment total carbon content, while C. decorus showed a significant positive correlation with these variables; C. crassicaudatus did not show any significant correlation with either of these variables. The algal composition in the pooled data from both lakes was another important factor affecting the larval distributions. The proportion of G. paripes and C. decorus larvae increased with filamentous algal density, and C. crassicaudatus larvae with increasing Cyanobacteria. Although both study lakes were very shallow, the effect of water depth (alone or shared with environmental variables) on chironomid larval community composition was substantially higher than the seasonality (sampling month) effect.