Estuarine eutrophication, nutrient load reduction, and benthic ecological condition in the Pagan River watershed, Smithfield, Virginia

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Cate Turner, Lisa Horth and Daniel M. Dauer, Department of Biological Sciences, Old Dominion University, Norfolk, VA

Background/Question/Methods
Recovery of the benthic community in a previously degraded ecosystem was assessed in the Pagan River in Smithfield, Virginia. The Pagan River is a shallow tributary of the James River with a drainage basin spanning approximately 185 km² and ranges in salinity from freshwater (<0.5 ppt) to low polyhaline (18-23 ppt). This hypertrophic ecosystem, caused by organically enriched wastewater from the Smithfield Foods meat processing plants, had not been studied since the cessation of the effluent in the mid 1990’s. Previous studies classified the Pagan River as severely degraded, showing an overabundance of pollution indicative taxa and the highest nutrient loads ever recorded in the Chesapeake Bay. The benthos was sampled at 25 random stations in the Pagan River using a 0.04m² Young grab. Benthic macroinvertebrates were identified to obtain species diversity, abundance, and biomass data. The Benthic Index of Biotic Integrity was used to classify the ecological condition of the benthic communities for comparison to previous studies.
Results/Conclusions
While abundance decreased significantly since 1996 (t-test, t=4.43, p <0.001), the Pagan River benthic communities were still classified as severely degraded. Future studies can record the recovery in the Pagan River to track the condition following such a large scale pollution event.