Stratification of Southern Georgia Streams For Rapid Bioassessment Focusing on Differences in Structure and Function of Black Water and Clear Water Streams

As part of a rapid bioassessment project for the state of Georgia, relatively unimpaired reference streams and impaired sites were sampled for biological, chemical and physical parameters, and macroinvertebrates were identified. The metrics, biological, physical and chemical metrics, were selected using Ecological Data Application System Version 3.3.2k (EDAS). Discrimination efficiency and correlations were performed to determine the best metrics that separated impaired streams from reference streams and later on to form the index of stream water quality. Principal components analysis of the selected metrics showed that some of the blackwater reference streams and clearwater reference streams are randomly placed over the ordination space and a few of the black water reference streams and a few of the clear water reference streams formed distinct clusters. As a result, the black water and clear water streams were analyzed as two different stream types. In Southern coastal plain ecoregion the compositional metrics are the dominant forms of metrics in streams. When the blackwater streams and clearwater streams were analyzed as two different stream types, different macroinvertebrate metrics characterized blackwater and clearwater streams within the two ecoregions. The metrics that formed the indices were more efficient in discriminating impaired and reference streams when separated into the two stream types. Index values were higher; demonstrating the better performance of the metrics. The percentage of reference streams\u27 in excellent condition is higher in independent analysis. It can be concluded that within the constraints of RBP; metrics were able to distinguish slightly the two stream types, which in turn proved the requirement of a different set of reference criteria, and a different stress response for the metrics of both stream types, that will enhance the results and in turn the judgment