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Responses of Phytoplankton and Hyalella azteca to Agrichemical Mixtures in a Constructed Wetland Mesocosm

Richard E. Lizotte Jr., Sam Testa III, Martin A. Locke, R. Wade Steinriede Jr.
Archives of environmental contamination and toxicology 2013 v.65 no.3 pp. 474-485
Hyalella azteca, agricultural runoff, agricultural watersheds, atrazine, bioassays, constructed wetlands, environmental impact, metolachlor, nitrogen, nutrients, permethrin, phosphorus, phytoplankton, pollutants, sediments, toxicity, trapping
We assessed the capability of a constructed wetland to mitigate toxicity of a variety of possible mixtures, such as nutrients only (NO) (nitrogen [N], phosphorus [P]), pesticides only (PO) (atrazine, S-metolachlor, permethrin), and nutrients + pesticides on phytoplankton chlorophyll-a, on 48-h aqueous Hyalella azteca survival and 10-day 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- to 10 -fold at 7 days after NO treatment. However, responses of chlorophyll-a to PO 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 PO and nutrients + pesticides treatments in association with permethrin concentrations. H. azteca sediment survival was unaffected, whereas 10-day growth decreased within 1 day of dosing at all sites during nutrients + pesticides treatment. Constructed wetlands were shown to be an effective agricultural best-management tool for trapping pollutants and mitigating ecological impacts of run-off in agricultural watersheds.