Document Type

Report

Publication Date

8-2014

Pages

103 pp.

Abstract

Executive Summary

The subtidal macrobenthic communities off Money Point in the Southern Branch of the Elizabeth River were quantitatively sampled in summer 2010 (Dauer 2011). The designated Money Point study area was part of a sediment contaminant remediation effort. The primary objectives of the present study were to: (1) characterize the biological health of the benthos of Money Point comparing pre-remediation (2010) and post-remediation (2013) conditions and (2) assess the effectiveness of the sediment contamination remediation efforts with respect to Money Point benthos. In this report the macrobenthic communities off Money Point were resampled in the summer of 2013 after the completion of the sediment contamination remediation efforts.

Dauer (2011) characterized the benthic community condition off Money Point as consistent with previous characterizations of the Elizabeth River watershed: (1) benthic community species diversity and biomass were below reference condition levels; (2) abundance often above reference condition levels and considered excessive; and (3) community composition was 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 as sampled in 2010 had (1) the lowest average B-IBI value, 2.0, a level characterized as severely degraded; (2) relatively high abundance levels, exceeding 6,000 individuals per m 2; (3) the lowest Shannon Diversity Index value; and (4) the lowest biomass level. 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.

In 2013 the benthic community showed (1) a significant increase in the value of the B-IBI from 2.0 to 2.3; (2) a highly significant reduction in abundance levels from 6,012 to 2,640 individuals per m2; (3) a highly significant increase in the Shannon Diversity Index value from 1.64 to 2.33; and (4) a highly significant increase in the level of biomass from 0.35 to 0.85 AFDW gC per m2. The increase in the species diversity (H’) was due to both an increase in species richness (the species per sample increase significantly from 9.64 to 11.96) and lower dominance by two pollution indicative polychaete species (Mediomastus ambiseta and Streblospio benedicti) from a combined level of 4,956 individuals per m2 in 2010 to 1,244 individuals per m2 in 2013. Those levels of these two species represented, respectively, 82.4% of the individuals in 2010 and only 47.1% of the individuals in 2013.


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