Congruence between nutrient water quality parameters and Chironomidae ( Diptera ) in delineating ecological classifications of Missouri streams at different environmental scales

SUMMARY 1. Large scale classifications such as nutrient ecoregions have been established in the United States to help regulate surface water resources. These classifications and their constituent classes are hypotheses which may be tested by establishing the strength of the classes to differentiate within class and between class variation. The purpose of our study was to test the strength of three different classification schemes at three different scales: landscape (nutrient ecoregion), watershed (hydrologic unit), and microhabitat (substrate) using Chironomidae community assemblage and metric data and nutrient water quality data. Furthermore, we tested for congruence of classes using nutrient water quality and chironomid community data for the three classification schemes in an attempt to link the biota to nutrient concentrations. 2. Historical data on chironomid communities were compiled from the 20 stream sites in Missouri over multiple years and seasons. Nutrient water quality data were also collected at these sites but under a different study. An analysis of variance was used to determine whether chironomid metrics and nutrient water quality parameters varied significantly between classes for each of the classification schemes. Chironomid community assemblages and metrics and nutrient water quality parameters were used to test the strength of each classification. A mantel test for congruence was used to determine how congruent the classes were for each classification scheme based on three data matrices: chironomid community assemblages; chironomid metrics; and nutrient water quality parameters. 3. The three classification schemes were robust enough to show significant variation between nutrient water quality concentrations, chironomid community assemblages, and chironomid metrics. The classifications based on the nutrient data were strong and the classifications based on the chironomid assemblage and metric data were weak, although comparable to classification strengths based on entire macroinvertebrate communities and fish communities for regional, watershed/basin, and substrate classes. 4. Despite relatively weak classification based on chironomid data, all data were able to separate out the different nutrient ecoregions. Variation from classes of watershed and basin that transcended nutrient ecoregions and from substrates at a very fine environmental filter were not strong enough to break up the grouping of nutrient ecoregions, and therefore were not responsible for the relatively weak classification strengths observed. Finally, the chironomid metric and assemblage data were significantly congruent with the nutrient data but were not strongly correlated indicating that nutrient and biological data can be combined under the nutrient ecoregion classification, but with some caution. 3 Introduction Classifications …