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Effects of a pulsed treatment with the herbicide afalon (active ingredient linuron) on macrophyte‐dominated mesocosms. I. Responses of ecosystem metabolism
Author(s) -
Kersting Kees,
Van Wijngaarden René P.A.
Publication year - 1999
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.5620181229
Subject(s) - mesocosm , zoology , ecosystem , macrophyte , ec50 , chemistry , biomass (ecology) , oxygen , environmental chemistry , environmental science , ecology , biology , biochemistry , organic chemistry , in vitro
Experimental drainage ditches used as mesocosms were treated with linuron three times, at 4‐week intervals, at nominal concentrations of 0, 0.5, 5, 15, and 50 μg/L. After each treatment, the mesocosms were kept static for 1 week. They were then flushed with noncontaminated surface water, with a residence time of 5 d, until the next treatment. Structural and functional measurements were made. A companion paper discusses the structural aspects. Dissolved oxygen concentrations and pH were measured continuously at 15‐min intervals. Both variables declined during the static periods, and a lowest‐observed‐effect concentration (LOEC) of 5 μg/L was noted for both response variables. All mesocosms recovered during the flushing periods. Diurnal oxygen curves were used to calculate ecosystem gross primary production (GPP) and ecosystem oxygen consumption. Ecosystem oxygen consumption was not affected by the linuron treatments, but GPP had an EC50 of 21 μg/L during the static period after the first treatment. The EC50 for GPP increased to 36 μg/L after the second treatment and to 80 μg/L after the third treatment. This increase in EC50 is interpreted as an adaptation of the ecosystem, the mechanism of which could not be identified. The LOEC was 15 μg/L for all treatments and did not change over time. Between treatments, GPP recovered to the level of the controls. The LOEC for the long‐term GPP was 50 μg/L.