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Effects of Glyphosate and Two Herbicide Mixtures on Microbial Communities in Prairie Wetland Ecosystems: A Mesocosm Approach
Author(s) -
Sura Srinivas,
Waiser Marley,
Tumber Vijay,
Lawrence John R.,
Cessna Allan J.,
Glozier Nancy
Publication year - 2012
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2011.0376
Subject(s) - glyphosate , mesocosm , biomass (ecology) , mcpa , agronomy , simazine , dicamba , mecoprop , ecosystem , biology , environmental chemistry , environmental science , ecology , chemistry , pesticide , weed control , atrazine
A multitrophic outdoor mesocosm system was used to mimic a wetland ecosystem and to investigate the effects of glyphosate and two herbicide mixtures on wetland microbial communities. The glyphosate concentration used was 1000 times the environmentally relevant concentration (ERC). One herbicide mixture consisted of six auxin‐type herbicides (2,4‐D, MCPA, clopyralid, dicamba, dichlorprop, mecoprop), each at 1000 times the ERC. The second mixture was comprised of eight herbicides, including the six auxin‐type herbicides as well as bromoxynil and glyphosate. For this mixture, a dose‐response approach was used to treat mesocosms with the ERCs of each herbicide as the base concentration. Algal biomass and production and bacterial production and numbers for pelagic and attached communities were measured at different times over a 22‐d period. The experimental results indicate that the eight‐herbicide mixture, even at low concentrations, produced negative effects on microbial communities. Glyphosate on its own suppressed algal biomass and production for the duration of the study in pelagic and biofilm communities. Algal biomass and production, although initially depressed in the auxin‐type herbicide treatment, were stimulated from Day 9 until experiment end. Due to their similar modes of action, the effects of this herbicide mixture appear to be a result of concentration addition. Such negative effects, however, were brief, and microbial communities recovered from herbicide exposure. Based on evidence presented in this study, it appears that glyphosate has a higher potential to inhibit primary production and chlorophyll a content in pelagic and attached wetland algal communities than the auxin‐type herbicide mixture.