UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Mississippi oxbow lake sediment quality during an artificial flood
Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 9, 2009
Publication Date: January 29, 2009
Citation: Knight, S.S., Lizotte Jr, R.E., Moore, M.T., Smith Jr, S., Shields Jr, F.D. 2009. Mississippi oxbow lake sediment quality during an artificial flood. Bulletin of Environmental Contamination and Toxicology, 82(4): 496-500. DOI 10.1007/s00128-009-9653-4 [on line].
Interpretive Summary: Oxbow lakes of the Mississippi Delta often become very shallow during the dry days of summer. Pumping water into these lakes has been proposed as a way of improving habitat. Because river water may contain pollutants such as pesticides, lake sediment toxicity was measured during an experiment where river water was pumped into an oxbow lake along the Coldwater River, Mississippi. Sediment toxicity was measured using a common water animal called a scud. These tiny relatives of crayfish are useful as test animals because they are sensitive to pollution. While results showed that pumping did not affect scud survival, growth was suppressed. This was attributed to a complex interaction of the pesticides atrazine, and fipronil sulfone and their by-products that was in the river water. Both Atrazine and metolachlor were shown to increase over the course of the study which was likely due to increased runoff associated with hurricanes Katrina and Rita that had occurred prior to the study. This research should help water resource managers and scientist better understand the relationships between agricultural pollutants and aquatic organisms and their habitats.
Surface sediment quality was assessed during a 35-day artificial flood in a shallow (<1.5 m) oxbow lake along the Coldwater River, Mississippi, using Hyalella azteca 28-day bioassays. Seventeen pesticides were monitored in sediments before, during and after flooding, with increases in atrazine and metolachlor concentrations coinciding with two unexpected storm events, 51 and 56 mm, during and after flooding, respectively. Mean 28-day H. azteca survival was >85% throughout this study. However, growth was affected at three sites during flooding with limited growth recovery after flooding. Patterns in observed growth impairment were associated with changes in atrazine and fipronil sulfone concentrations.