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The response of biota in experimental stream channels to a 24‐hour exposure to the herbicide Velpar L®
Author(s) -
Schneider Judith,
Morin Antoine,
Pick Frances R.
Publication year - 1995
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620140921
Subject(s) - biota , environmental science , environmental chemistry , chemistry , ecology , biology
Outdoor experimental stream channels were used to examine the short‐term impact of Velpar L® on periphyton and macroinvertebrates. Velpar L was added to five channels for 24 h while five additional, alternating channels served as controls. The concentration and the duration of the Velpar L treatment were chosen to mimic the pulse of herbicide carried to streams during rain events subsequent to Velpar L spraying. The mean concentration of hexazinone, the active ingredient, in the treatment channels varied over time from 145 μg L −1 to 432 μg L −1 . Periphyton chlorophyll‐ a ‐specific productivity was reduced by 80% during the Velpar L addition. Within 24 h after the termination of the Velpar L addition, periphyton productivity returned to control levels. The 4‐h EC50 value, 3.6 μg L −1 of hexazinone, for chlorophyll‐ a ‐specific productivity was lower than published bioassay results from single species tests. Mean periphyton biomass (chlorophyll‐ a per unit area of gravel substrate) and mean macroinvertebrate biomass, density, length, and drift were not significantly affected by the Velpar L addition. Although it appears that lotic systems are resilient to short‐term exposure to Velpar L, the effects of repeated and chronic exposures on stream biota remain unexplored.