You are here:
COMPARISON OF TWO INDICES OF BENTHIC COMMUNITY CONDITION IN CHESAPEAKE BAY
Citation:
Ranasinghe, J. A., D. E. Russell, F W. Kutz, J. B. Frithsen, J F. Paul, R. Batiuk, J. L. Hyland, J. Scott, AND D. M. Dauer. COMPARISON OF TWO INDICES OF BENTHIC COMMUNITY CONDITION IN CHESAPEAKE BAY. Presented at Environmetrics, Las Vegas, NV, September 18-20, 2000.
Impact/Purpose:
The primary objectives of this research are to:
Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;
Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;
Develop and validate multivariate models based on quantification studies;
Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;
Complete an initial draft (potentially web based) of a national landscape condition assessment.
This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.
Description:
The Chesapeake Benthic Index of Biotic Integrity (B-IBI) and the EMAP-VP Benthic Index were applied to samples from 239 sites in Chesapeake Bay. The B-IBI weights several community measures equally and uses a simple scoring system while the EMAP-VP Benthic Index uses discriminant function coefficients to weight variable contributions. The two indices agreed on degraded or undegraded classifications for benthos at 85% of these sites. The indices were strongly associated with Pearson and Spearman correlation coefficients of 0.78 and 0.76, respectively. The 35 sites where the indices disagreed were scattered in different habitats throughout the Bay, and were most often located between areas with predominantly degraded and predominantly undegraded sites. Many of the classification disagreements were at sites with index values close to, but on opposite sides of, the degraded-undegraded thresholds. We prefer using the B-IBI because there were indications that the EMAP-VP index did not detect some subtle degradation effects, the B-IBI incorporates information from more ecological categories, and the B-IBI is easily decomposed to identify community attributes contributing to degraded site classifications.