Document Type

Report

Publication Date

7-2000

Pages

74 pp.

Abstract

Executive Summary

A study of the macrobenthic communities of the Elizabeth River watershed was conducted in summer 1999. The three objectives of the Benthic Biological Monitoring Program of the Elizabeth River watershed are: (1) To characterize the health of regional areas of the tidal waters of the Elizabeth River watershed Chesapeake Bay as indicated by the structure of the benthic communities. These characterizations are based upon application of benthic restoration goals and the Benthic Index of Biotic Integrity (BIBI) developed for the Chesapeake Bay to five primary strata - the Mainstem of the river, the Lafayette River, the Southern Branch, Western Branch and Eastern Branch. Within each stratum samples were randomly allocated in a probability-based sampling design. A probability-based sampling design allows calculation of confidence intervals around estimates of condition of the benthic communities. ( 2) To conduct trend analyses on long-term data at 14 fixed-point stations to relate temporal trends in the benthic communities to changes in water and/or sediment quality. Trend analyses will be updated annually as new data are available. (3) To produce an historical data base that will allow annual evaluations of biotic impacts by comparing trends in status within probability-based strata and trends at fixed-point stations to changes in water and/or sediment quality. In addition in the 1999, sampling event two additional strata were sampled for benthic community condition: (1) Scuffletown Creek, a proposed location for sediment contaminant remediation and (2) an additional nearby small creek system - the Jones and Gilligan Creek complex.

The condition of the seven strata was compared to the results for all Virginia tidal waters for 1999 based upon the random sampling of 100 sites as part of the on-going Virginia Benthic Monitoring Program. In 1999 Virginia tidal waters averaged 30% degraded benthic bottom. All seven strata for the Elizabeth River were higher than this value - 52% for the Mainstem of the River, 64% for the Lafayette River, 64% for the Eastern Branch, 72% for the Western Branch and 92% for the Southern Branch. Scuffletown Creek and Jones-Gilligan Creek both averaged 76% area failing the Benthic Restoration Goals. In general for all Elizabeth River strata, species diversity and biomass were below reference condition levels while abundance values were within reference condition levels. Community composition was unbalanced with levels of pollution indicative species above and levels of pollution sensitive species below reference conditions. The only exceptions to these patterns was the Mainstem of the river where biomass and levels of pollution sensitive species were within reference condition levels.


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