Effects of drift from 39 aerially-applied herbicides on production pond plankton and water quality

Authors: PERSCHBACHER, PETER - UAPB; Ludwig, Gerald; EDZIYIE, REGINA - UAPB

Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 10/15/2006
Publication Date: 2/26/2007
Citation: Perschbacher, P., Ludwig, G.M., Edziyie, R. 2007. Effects of drift from 39 aerially-applied herbicides on production pond plankton and water quality [abstract]. Book of Abstracts Aquaculture America. p. 704.

Interpretive Summary:

Technical Abstract: Thirty-nine, aerially-applied row crop herbicides were tested for possible adverse effects from drift on fish pond plankton and water quality over 10 years of testing at the University of Arkansas at Pine Bluff. Phytoplankton biomass and productivity, 6 water quality parameters of interest in aquaculture, and zooplankton composition and density were measured at four herbicide levels in triplicate 500-L outdoor, pool mesocosms. Treatments were designed to evaluate simulated overspraying, and drift at low (1% of full field rates) and high levels (10% of the full rate) to production ponds, and no drift (control). Herbicides were evaluated at the approximate times of field application. Water was pumped from an adjacent production pond into pools on the day of the test and an initial preapplication water sample taken. Herbicide (without additives) was sprayed on the pool surface and evaluations repeated at 24 and 48 h post- application. If drift effects were noted, selective evaluations were continued until morning oxygen levels did not differ from (or approximated) those of controls (ie. recovery). Of the herbicides tested, only diuron (applied in March for burndown prior to cotton planting) and atrazine drift (87% of the major aerial corn herbicide-Basis GoldTM and applied April-May) produced significant effects on the suite of 10 parameters . Diuron affected oxygen production in relation to dose. Chlorophyll a levels dropped to 22% of control after 2 weeks at high drift and then slowly increased to 80% of control levels by the end of sampling at 4 weeks (recovery). As a result of the inhibition of oxygen production and reduced plankton levels, morning oxygen levels fell to critical levels of 3 ppm and below after 1 week in the high drift treatment. Zooplankton were also reduced relative to control levels at both drift levels. Positive impacts noted from high drift included reduced levels of off flavor-producing Anabaena beginning at one week, with essentially complete elimination after 3 weeks, and reduced unionized ammonia. Atrazine primarily affected zooplankton. Rotifer populations compared to controls were 56% lower on day 2 at the 10% rate and 78% lower on day 7 at the 1% rate. Nauplii and adult copepods were lower on day 3 at both drift rates, but only significant at the low drift rate. Diuron high drift concentration in the pools was 0.02 ppm (double the recommended weekly off-flavor treatment) and of concern in production ponds. Atrazine high drift was 0.01 ppm and not of concern to production pond water quality. Drift from both herbicides would seem to be problematic to fry ponds through reduced zooplankton, however later testing with water from a simulated fry pond indicated that the low levels of chlorophyll a in the fry pond resulted in lessened effects of the herbicides.