A benthic index of biological integrity for assessing habitat quality in estuaries of the southeastern USA

A benthic index of biotic integrity was developed for use in estuaries of the southeastern USA (Cape Henry, VA; St. Lucie Inlet, FL) using a modification of the method developed by Weisberg et al. (1997. An estuarine benthic index of biotic integrity (B-IBI) for Chesapeake Bay. Estuaries, 20 (1), 149–158). Data from non-degraded stations sampled in 1993 and 1994 were analyzed using classification analysis of species composition to define major habitat types relative to selected physical parameters. Various benthic metrics were then tested on a larger 1994 data set for each major habitat to determine those that discriminated between non-degraded and degraded sites classified on the basis of dissolved oxygen, sediment chemistry, and sediment toxicity results. Scoring criteria for each metric were developed based on the distribution of values at non-degraded sites. Average scores from different combinations of the most sensitive metrics were compared to derive the final index, which integrates the average scores of four metrics (number of taxa, abundance, dominance, and percent sensitive taxa). An independent data set representing sites sampled in 1993 and 1995 was used to validate the index. The final combined index correctly classified 93% of stations province-wide in the developmental data set and 75% of stations in the validation data set. Comparison of the index results with those of individual benthic measures and sediment bioassays from stations sampled in 1993 and 1995 showed that the index detected a higher percentage of samples where bioeffects were expected (based on sediment chemistry) than did any of these other measures individually.