Location: Water Quality and Ecology Research
Title: Responses of phytoplankton and Hyalella azteca to agrichemical mixtures in a constructed wetland mesocosms Authors
Submitted to: Archives of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2013
Publication Date: N/A
Interpretive Summary: We examined nutrient and pesticide effects on algae and an aquatic invertebrate animal, Hyalella azteca, in a divided constructed wetland. We looked at how well this constructed wetland could decrease the effects of a variety of different agricultural contaminant mixtures such as nutrients only (nitrogen+phosphorus), pesticides only (atrazine, metolachlor, and permethrin) and nutrients+pesticides on algae and aquatic animals. Water and wetland soil was obtained along the length of the wetland at 10 m, 20 m, and 40 m distance from the contaminant source. The study showed algae increased in nutrients only contamination while decreasing at some distances during pesticides only and nutrients+pesticides only contamination. Animal survival in wetland water decreased up to 20 m within the first two days after pesticides only and nutrients+pesticides contamination coinciding with permethrin levels. Animal survival in wetland soil was not affected by agricultural contamination but animal growth was less at all sites after one day after contamination with nutrients+pesticides. Our study showed that constructed wetlands are effective at decreasing the effects of a variety of multiple agricultural contaminant mixtures with nutrients and pesticides in wetland water and soil. Our results are of interest to regulatory and other agencies and the pesticide industry by providing additional information to improve and sustain river, stream and lake water quality and overall environmental quality using constructed wetlands as an effective conservation practice.
Technical Abstract: We assessed the capability of a constructed wetland to mitigate toxicity of a variety of possible mixtures such as nutrients only (N, P), pesticides only (atrazine, S-metolachlor, permethrin), and nutrients+pesticides on phytoplankton chlorophyll a, 48 h aqueous Hyalella azteca survival, and 10 d sediment H. azteca survival and growth. Water and sediment were collected at 10, 20, and 40 m distances from inflow and analyzed for nutrients, pesticides, chlorophyll a, and H. azteca laboratory bioassays. Phytoplankton chlorophyll a increased 4-10 fold 7 d after nutrients only treatment. However, responses of chlorophyll a to pesticides only and nutrients+pesticides were more complex with associated decreases at only 20 m for pesticides only and 10 and 40 m for nutrients+pesticides treatments. H. azteca aqueous survival decreased within the first 48 h of dosing at 10 and 20 m distances during pesticides only and nutrients+pestcides treatments in association with permethrin concentrations. H. azteca sediment survival was unaffected while 10 d growth decreased within 1 d of dosing at all sites during nutrients+pesticides treatments. Constructed wetlands were shown to be an effective agricultural best management tool for trapping pollutants and mitigating ecological impacts of runoff in agricultural watersheds.