Statistical verification of the Chesapeake Bay benthic index of biotic integrity

Abstract

SUMMARYThe benthic index of biotic integrity (B-IBI) developed for the Chesapeake Bay was statistically verified using simulations and a suite of multivariate statistical techniques. The B-IBI uses a simple scoring system for benthic community metrics to assess benthic community health and to infer environmental quality of benthic habitats in the Bay. Overall, the B-IBI was verified as being sensitive, stable, robust and statistically sound. Classification effectiveness of the B-IBI increased with salinity, from marginal performance for tidal freshwater ecosystems to excellent results for polyhaline areas. The greater classification uncertainty in low salinity habitats may be due to difficulties in reliably identifying naturally unstressed areas or may be due to regional ecotones created by stress gradients. Pollution-indicative species abundance, pollution-sensitive species abundance, and diversity (Shannon's index) were the most important metrics in discriminating between degraded and non-degraded conditions in the majority of the habitats. Single metrics often performed as well as the multi-metric B-IBI in correctly classifying the relative quality of sites. However, the redundancy in the multi-metric B-IBI provided a stable 'weight of evidence' system which increased confidence in general conclusions. Confidence limits developed for the B-IBI scores were used to distinguish among habitats that were degraded, non-degraded, of intermediate quality, or of indeterminate condition.

Least-Desired Index for Assessing the Effectiveness of Grass Riparian Filter Strips in Improving Water Quality in an Agricultural Region

“…The results of Alden et al (2002) indicated that the B-IBI is sensitive, stable, robust, and statistically sound. New sets of metric and threshold combinations for the tidal freshwater and oligohaline habitats were also developed in Alden et al (2002) with a larger dataset than was available to Weisberg et al (1997) for these two habitats. The present document includes the latest updates and the necessary information to calculate the Chesapeake Bay B-IBI.…”

“…Metrics for these two last habitats were developed in Alden et al (2002). The metric selection process was based on Mann-Whitney U tests for differences in means between the reference and the degraded sites of the index development data sets, and on consistency with ecological principles (Weisberg et al 1997).…”

“…In addition, a series of statistical and simulation studies were conducted to evaluate and optimize the B-IBI (Alden et al 2002). The results of Alden et al (2002) indicated that the B-IBI is sensitive, stable, robust, and statistically sound.…”

“…In addition, a series of statistical and simulation studies were conducted to evaluate and optimize the B-IBI (Alden et al 2002). The results of Alden et al (2002) indicated that the B-IBI is sensitive, stable, robust, and statistically sound. New sets of metric and threshold combinations for the tidal freshwater and oligohaline habitats were also developed in Alden et al (2002) with a larger dataset than was available to Weisberg et al (1997) for these two habitats.…”

Review and evaluation of estuarine biotic indices to assess benthic condition

“…Among the possible reasons for the observed lack of sensitivity and robustness may be the chosen tested metrics. According to Alden et al (2002), four metric groups proposed by Weisberg et al (1997) proved to be significantly important to distinguish degraded from reference sites (diversity, productivity, species composition, and trophic composition). Nonetheless, for this particular case three submetrics seem to be the most important: pollution indicative taxa, pollution sensitive taxa, and diversity.…”