Journal
ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY
Volume 24, Issue 5, Pages 1281-1286Publisher
WILEY
DOI: 10.1897/04-256R1.1
Keywords
esfenvalerate; Cloeon dipterum; population level; compensation; intraspecific competition
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Results of environmental risk assessments based merely on toxic effects of contaminants at the individual level, without consideration of population-level effects, may be questionable. The aim of the present study was to investigate how limited food resources, resulting in. intraspecific competition, could interact with the chronic effect of short-term contamination with the insecticide esfenvalerate. Larvae of the mayfly, Cloeon dipterum, were exposed to esfenvalerate (0.00 1 - 100 mu g/L) for 1 h and then transferred to indoor microcosms containing insecticide-free water, where they were maintained at various food levels until emergence. The results showed that short-term exposure to 10 or 100 mu g/L resulted in acute mortality. Chronic effects on survival occurred at concentrations up to three orders of magnitude lower than that causing the acute effect (0.01 mu g/L). Food limitation increased effects on organisms during medium-term observation (8-15 d), but assessment of long-term survival rates suggested that the chronic effects of low insecticide concentrations could be compensated for, at least regarding some endpoints. The authors assume that in limited-food conditions, lethal and sublethal effects reduced competition between individuals, resulting in significantly increased final survival.
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