Document Type

Report

Publication Date

8-2011

Pages

99 pp.

Abstract

Executive Summary

The subtidal macrobenthic communities off Money Point in the Southern Branch of the Elizabeth River were quantitatively sampled in summer 2011. The designated Money Point study area will be a part of a sediment contaminant remediation effort. The primary objectives of this study were to: (1) characterize the biological health of the benthos of Money Point and (2) produce an historical data base that will allow an assessment of the effectiveness of the proposed sediment contamination remediation efforts with respect to Money Point benthos.

The most quantitative characterization of the benthos of the Elizabeth River watershed was the random sampling program conducted by the Benthic Ecology Lab of Old Dominion University from 1999 to 2007. This program combined the application of the Benthic Index of Biotic Integrity (B-IBI) developed for the Chesapeake Bay and probability-based sampling to calculate confidence intervals around estimates of condition of the benthic communities and allowed estimates of the areal extent of degradation of the benthic communities.

This study estimated the level of degraded benthic bottom of Money Point as 96% ± 4.0% - the highest level of degradation recorded by any previous studies in the Elizabeth River watershed. Previous quantitative areal estimates of benthic degradation in the watershed have varied from 52 ± 19.6% in 2001 to 84 ± 12.7% in 2005.

In general the benthic community condition off Money Point was consistent with previous characterizations of the Elizabeth River watershed: (1) benthic community species diversity and biomass below reference condition levels; (2) abundance often above reference condition levels and considered excessive; and (3) community composition unbalanced with levels of pollution indicative species above, and levels of pollution sensitive species below, reference conditions.

Compared to previous characterizations of the benthos of the Elizabeth River, the Money Point benthos had (1) the lowest average B-IBI value, 2.0, a level characterized as severely degraded (Figure 5); (2) the lowest Shannon Diversity Index value (Figure 8); and (3) the lowest biomass level (Figure 7). The low level of biomass is probably indicative of poor ecological value of the benthos as a food source for higher trophic levels, i.e fish, crabs, birds, etc.

Previous unpublished field experiments conducted by the ODU Benthic Ecology Lab in the Southern branch of the Elizabeth River, indicate that when total PAH levels are remediated to 45 ppm or less that significant benthic recruitment from indigenous populations will occur. Such recruitment levels are also likely to be sufficient to improve the condition of the benthos as measured by the B-IBI, to levels significantly above those in this study.


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