Tuesday, May 27, 2008
189

Benthic macroinvertebrate community response to an effluent in a complex river system

Richard A. Connelly1, Jeff M. Boltz1, and G. Scott Shoemaker2. (1) EA Engineering, Science, and Technology, Inc., 15 Loveton Circle, Sparks, MD 21152, (2) Upper Potomac River Commission, 528 Maryland Avenue, Westernport, MD 21562

Macroinvertebrate bioassessments were conducted in the North Branch of the Potomac River, Maryland in 2004 and 2006 as required by a wastewater treatment plant’s discharge permit and as part of continued long term benthic monitoring.  The treatment plant processes primarily paper mill effluent with a smaller component of municipal wastewater.  The objective of the studies was to assess the benthic community at locations upstream and downstream of the discharge point to determine if differences existed which were attributable to the effluent, while also considering tributary and other upstream influences on the benthic community.  Acid mine drainage, stormwater, construction, dams, and urbanization all influence the upper watershed.  The benthic IBI varied annually rating the stations just downstream of the discharge as poor to very poor, improving to fair further downstream.  The upstream reference was rated as fair but a station just upstream of the discharge ranged from poor to very poor, although the individual metrics indicated different trends contributing to the low ratings than at the downstream stations.  The results suggest that organic or nutrient enrichment was the primary causative factor for the low ratings downstream.


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