Elsevier

Chemosphere

Volume 41, Issue 10, November 2000, Pages 1511-1517
Chemosphere

Toxicity of fenvalerate to caddisfly larvae: chronic effects of 1- vs 10-h pulse-exposure with constant doses

https://doi.org/10.1016/S0045-6535(00)00107-7Get rights and content

Abstract

Episodic pollution events such as runoff or spraydrift can lead to a short-term (few hours) contamination of aquatic ecosystems with pesticides. So far, different short-term exposures with respect to long-term effects have not been studied. In the present study, caddisfly larvae, typical for agricultural streams (Limnephilus lunatus Curtis, 2nd and 3rd instar) were exposed for 1- vs 10-h to three different equivalent doses (μg h) of fenvalerate. After transfer into an artificial stream microcosm with pesticide-free water, chronic effects were observed over 240 days. Comparison of 1- and 10-h exposure revealed that 1-h contamination leads to stronger effects. The differences were significant for the sublethal endpoints emergence pattern and dry weight of adults (ANOVA, Fisher's PLSD; P<0.05). In terms of exposure dose, the difference between 1- and 10-h exposure equals a factor of 6 as a mean of all endpoints studied. The following significant effect levels for the 1-h exposure were obtained for the different endpoints investigated: reduced emergence success and production at 0.1 μg l−1, temporal pattern of emergence at 0.001 μg l−1, dry weight of adults at 0.01 μg l−1.

Introduction

Episodic pollution events cannot adequately be addressed by conventional toxicity testing methods with fixed duration continuous exposure. For example, the introduction of agricultural pesticides with a low water solubility, e.g., pyrethroids, into streams due to runoff, leads to short-term peak concentrations Baughman et al., 1989, Kreuger, 1995, Schulz et al., 1998, Liess et al., 1999. Concentrations in streams decrease quickly because of adsorption processes and the permanent water renewal Kreutzweiser and Sibley, 1991, Zwick, 1992. To obtain toxicity data relevant to the field situation, different short-term exposure scenarios must be compared and assessed.

To assess the effects of different short-term exposure times, equivalent doses (μg h) of chemicals can be compared. An increase of acute toxicity with decreasing exposure time has been demonstrated e.g., for Gammarus pulex and lindane (Abel, 1980) and for Aedes aegypti and different insecticides (Parsons and Surgeoner, 1991). Similar results exist for the chronic effects of brief exposure of Chironomus riparius to equivalent doses of cadmium (McCahon and Pascoe, 1991). Recent ecotoxicological studies have increasingly emphasized the importance of long-term observations of effects after short-term contamination Liess et al., 1993, Brent and Herricks, 1998, Hosmer et al., 1998. However, no information is available on the comparison of different short-term exposure times of aquatic invertebrates to insecticides with respect to long-term effects.

Aim of the present study is the comparison of 1- and 10-h exposure of a caddisfly species (Limnephilus lunatus Curtis, 2nd and 3rd instar larvae) to a pyrethroid insecticide (fenvalerate) using a long-term observation period (240 days) with different ecotoxicological endpoints: emergence success, emergence pattern, male–female ratio and dry weight of the adults. L. lunatus is one of the most abundant caddisfly species of lowland streams (Higler, 1981). Previous studies have demonstrated, that emergence of 5th instar larvae of L. lunatus is reduced at low lindane concentrations (Schulz and Liess, 1995) and that 1-h exposure to fenvalerate leads to a slight reduction of emergence success and a prominent alteration of the temporal emergence pattern (Liess and Schulz, 1996).

Section snippets

General

After short-term contamination (1 vs 10 h) in glass beakers the test organisms were transferred to an outdoor artificial stream microcosm containing pesticide free water. Different endpoints were monitored over a period of 240 days. Specimens of L. lunatus were collected from a small brook in a meadow north of Braunschweig, in northern Germany (Adenbüttler Mühlenriede (Liess et al., 1993), in which no pesticide contamination is detectable in water or suspended sediments) and stored for less

Phenology of emergence

Emergence took place between 88 days (13 June 1994) and 231 days (3 November 1994) after contamination. Between 33% and 14% of the 200 exposed larvae per setup emerged. Survival rate in the control group compares with previous and other studies using trichoptera larvae (Schulz and Liess, 1995). Total emergence after 1-h contamination was highest in the control setup and decreased with increasing dose. In the 10-h setup 0.001 μg h produced the highest total emergence being similar to that of the

Discussion

The present results clearly indicate that 1-h exposure leads to stronger effects than 10-h exposure with equivalent doses. The differences in terms of exposure concentration correspond factors between 2.5 and 10. Similar results have been obtained by the comparison of 1- and 10-h exposure of C. riparius to cadmium (McCahon and Pascoe, 1991); although no significant effects were found, short-term exposure to equivalent doses resulted in reduced survival to emergence of 1st and 4th instar larvae.

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