Efficacy of Sediment Contaminant Remediation of the Benthos in a Segment of the Southern Branch of the Elizabeth River

The bottom sediment of the Southern Branch of the Elizabeth River, a tributary of Chesapeake Bay, was historically contaminated with hydrocarbons from industrial sources especially wood treatment facilities. The Elizabeth River Project selected a section of the bottom off Money Point in the Southern Branch for a sediment contaminant remediation effort. Prior to initiation of remediation efforts, a survey occurred in summer 2010 to characterize the ecological condition of the benthic communities off Money Point compared to benthic communities of a benthic region across the channel and northwest of Money Point near Blows Creek. That study characterized the benthos of Money Point as significantly different from and degraded compared to that of Blows Creek using the Chesapeake Bay Benthic Index of Biotic Integrity. After the 2010 benthic community collection, the remediation effort removed approximately 20,000 cubic yards of contaminated sediment and covered the bottom with a sand cap. This phase of the remediation was completed in 2012. My study characterized the benthic communities of the same two field sampling strata at Money Point and Blows Creek in summer 2013 after the dredging and capping was completed. The benthic community condition was characterized using the multi-metric Chesapeake Bay Benthic Index of Biotic Integrity (B-IBI), abundance of individuals, biomass, species richness, and informational diversity. In comparing the pre-remediation and post-remediation benthic community condition, I used a fixed 2-factor ANOVA consistent with a BACI design (Before After Comparison Interaction). The B-IBI and all metrics showed improvements at Money Point, whereas the majority of metrics at Blows Creek showed a decrease. The B-IBI in particular decreased at Blows Creek by the same amount that Money Point increased, changes that would not be significant except when compared directly by the BACI style assessment. Comparison of biological metrics between sample periods at Money Point indicated a change from an opportunist dominated community to a more transitional community. A comparison of ratios of biomass to abundance and species richness to abundance further suggests a shift towards larger bodied organisms in less abundance than before remediation, indicative of an improved condition