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Title: Do varying aquatic plant species affect phytoplankton and crustacean responses to a nitrogen-permethrin mixture?

item Lizotte, Richard
item Moore, Matthew

Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2016
Publication Date: 1/14/2017
Citation: Lizotte Jr, R.E., Moore, M.T. 2017. Do varying aquatic plant species affect phytoplankton and crustacean responses to a nitrogen-permethrin mixture?. Bulletin of Environmental Contamination and Toxicology. 98(1):58-64.

Interpretive Summary: Agricultural runoff containing nitrogen fertilizer (ammonium nitrate) and insecticide (permethrin) mixtures can affect algae and crustaceans like Hyalella azteca. To address this, a series of small artificial wetlands planted with two species of aquatic plants, the common cattail and milfoil were dosed with nitrogen and permethrin to measure how well these different two different species of plants could decrease the effects of the nitrogen and insecticide mixture on algae and crustaceans. Water and wetland soil was collected from each of 16 small artificial wetlands. The study showed algal growth increased in response to nitrogen fertilizer in all wetlands but was greatest in the cattail wetlands. Crustacean survival and growth in soil were not affected in any wetland while survival in water was equally decreased in all wetlands within 4 hours of the addition of nitrogen and insecticide and improved within 1-2 days showing no differences among the two plant species. The study showed that different plant species had only a modest effect on algal growth and no effect on crustacean responses indicating that both plant species are effective at decreasing the effects of nitrogen fertilizer and insecticide permethrin 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 a variety of wetland plants as an effective conservation practice.

Technical Abstract: Hydraulically connected wetland microcosms vegetated with either Typha latifolia or Myriophyllum aquaticum were amended with an NH4NO3 and permethrin mixture to assess the effectiveness of both plant species in mitigating ecological effects of the pollutant mixture on phytoplankton (as chlorophyll a) and the crustacean Hyalella azteca. Peak aqueous concentrations occurred at 0.17 d ranging from 21.4-32.9 mg NH4/L, 29-37.4 mg NO3/L, 34.6-59.8 µg cis-permethrin/L and 24.7-48.5 µg trans-permethrin/L. No sediment samples had any detectable levels of permethrin. Phytoplankton grew in response to increased NH4NO3 in the presence of all plant species, but growth was greatest in T. latifolia microcosms by 7 d, and growth was unaffected by exposure to permethrin. Aqueous toxicity of the nitrogen-permethrin mixture to H. azteca occurred rapidly (0.17 d), was mitigated within 1-2 d, and aqueous toxicity was unaffected by plant species type. A toxic unit model approach ascertained the primary source of aqueous toxicity was permethrin with minimal additional toxicity from NH4NO3. No significant sediment toxicity was observed in H. azteca. Varying aquatic plant species had only modest influences on phytoplankton responses and no observable influence on animal responses during nitrogen-permethrin mixture exposures. As a result, both T. latifolia and M. aquaticum can be used as part of an effective agricultural best-management for mitigating pollutant impacts of agricultural run-off.