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PT05 Ecological Monitoring of Streams
(PT074) Assessment of instream communities associated with nutrient contributions from aquaculture discharges in the delta ecoregion.
Stephens, W1, Farris, J1, 1 Arkansas State University, State University, Arkansas, USA
ABSTRACT- Examination of commercial aquaculture discharges is a concern associated with nutrient contamination in the United States. Aquaculture production accounts for about 25,000 ha of the land use in Arkansas with the majority occurring in the Delta Ecoregion. Most of the economic contributions of this area originate from agriculture. Water quality impairments continue to exist in this production intensive landscape and as such, the regionally concentrated catfish industry has attracted attention to its possible contributions to basin contaminant loading. The condition of receiving streams assimilating aquaculture effluents has been characterized by the related assemblages of fish and aquatic macroinvertebrate communities. Assessment of two extensive commercial fish farm drainage systems in northeast Arkansas indicated no significant differences in benthic community responses (P = 0.192) between upstream, downstream and effluent receiving systems. However, one southeast Arkansas catchment site had a 50% reduction in macroinvertebrate taxa richness compared to a similar catchment in northeast Arkansas. Additional characterization of potential pond effluent impacts yielded significant (P < 0.05) differences in Ceriodaphnia dubia reproduction but no measured toxicity downstream of effluents. Significant (P < 0.05) C. dubia toxicity was however indicated in drainage systems in southeast Arkansas. Regional differences were apparent in the ability of this typical industrial drainage system to assimilate contaminants associated with aquaculture contributions. Distinguishing the status of ecoregion reference streams and ditch interfaces was critical to monitoring relative impacts and utilizing mitigation designs.
Key words: discharges, aquaculture, instream , assessments
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