Calibration of three florida biological indices using the biological condition gradient approach

The Florida Department of Environmental Protection (FDEP) has calibrated multi-metric indices for stream invertebrates, lake plant communities, and stream periphyton, using the Biological Condition Gradient (BCG) concept. We conducted a series of workshops, using the framework of Davies and Jackson (2006), with experts in both aquatic ecology and taxonomy. The panels reviewed, as individuals, taxonomic data from samples across a human disturbance gradient and they provided scores for those samples using the BCG framework. The groups then discussed the logic for each individual’s choice of category, and based on the ensuing discussion, panel members were then given the opportunity to modify their score. It is critical to note that the experts had no knowledge of the biological index scores, site location (other than sub-ecoregion), or any other physical, chemical, or site disturbance information. Thus, they made their decisions solely on the attributes of biological community structure and function inferred from the taxonomic and metric data. FDEP believes that the BCG is useful for calibrating and establishing biological criteria, since the BCG model is based upon sound, nationally accepted ecological concepts.