185 Environmental Toxicology and Chemistry, Vol. 20, No. 1, pp. 185–190, 2001  2001 SETAC Printed in the USA 0730-7268/01 $9.00 + .00 TOXICITY OF AQUEOUS-PHASE AND SUSPENDED PARTICLE-ASSOCIATED FENVALERATE: CHRONIC EFFECTS AFTER PULSE-DOSED EXPOSURE OF LIMNEPHILUS LUNATUS (TRICHOPTERA) RALF SCHULZ* and MATTHIAS LIESS Zoological Institute, Technical University, Fasanenstrasse 3, D-38092 Braunschweig, Germany ( Received 10 January 2000; Accepted 22 May 2000) Abstract—Non–point source pollution of agricultural surface waters via spray drift and runoff can lead to different short-term exposure scenarios: contamination with water-dissolved or particle-associated pesticide. To compare water-dissolved and particle- associated exposure, fenvalerate (FV) was tested in a 1-h exposure setup with suspended silt particles (5 g dry wt/L; total organic carbon = 3.2%). Chronic effects on the test organism Limnephilus lunatus Curtis (Trichoptera), second and third instar, were observed more than 240 d after transfer of larvae into an outdoor-stream microcosm with pesticide-free water. Significant-effect concentrations were 0.001 g/L in water and 0.2 g/kg in suspended sediments. Toxicity is lower in the presence of suspended particles by factors between 100 (using mortality and production of biomass as endpoints) and 10 (using emergence pattern and dry wt of adults as endpoints). Effect levels were generally lower than those in previous studies using older larval stages. The reduction of adult dry weight may diminish reproductive success. Aqueous-phase contamination caused lethal and sublethal effects at concentrations of FV that can be measured in the field. In contrast, levels of particle-associated FV that are relevant to the field situation elicited only sublethal responses in the present experiment. Results from this study suggest that short-term FV contamination at expected, field-relevant levels may lead to long-term effects even if the chemical is associated with suspended particles. Keywords—Caddis fly Ecological relevance Pyrethroids Sorption Suspended sediments INTRODUCTION Surface waters in agricultural areas are subject to transient pesticide contamination after field application of these com- pounds [1–4]. Spray drift and edge-of-field runoff are impor- tant routes of entry for chemicals, and the two may differ considerably in their resulting exposure scenarios. Spray drift leads to an input of pesticides dissolved in the water phase, whereas the contamination during runoff is sometimes largely based on pesticides associated with suspended particles [5]. After application onto agricultural fields, chemicals with low water solubility (e.g., pyrethroids) sorb to soil particles before their introduction into surface waters during heavy rainfall conditions [6]. Pyrethroids have been detected in water samples and as- sociated with bulk and suspended sediments. Reported peak concentrations of fenvalerate (FV) in streams and estuaries are 0.1 to 6 g/L [2,7–9] for the aqueous phase, 100 g/kg for FV associated with sediments, and 302 g/kg for FV asso- ciated with suspended particles [2,3,10]. The half-life of water- dissolved FV is between 1 and 2 d [11], whereas the half-life is between 27 and 42 d for sediment-associated FV [12]. In- troduction of insecticides via spray drift or runoff from agri- cultural fields into rivers leads to short-term exposure, because these insecticides are present in peak concentrations for only a few hours at most [4,13]. Studies regarding the toxicity of particle-associated FV re- fer mainly to bulk sediment–water systems that are represen- tative of the estuarine environment [10,14–16]. Most of these studies do not permit direct comparison of aqueous-phase and particle-associated FV toxicity. However, Clark et al. [15] demonstrated that the toxicity to marine crustaceans is reduced * To whom correspondence may be addressed(r.schulz@tu-bs.de). by a factor of approximately 9,700 in the presence of sedi- ments. Factors like this are expected for the sediment–water partitioning of FV according to the equilibrium partitioning theory [17]. Addition of very large amounts of suspended sediments (67 g/L) reduced the acute toxicity of permethrin and cypermethrin by a factor of approximately 250 [11]. A review by Coats et al. [18] summarized similar toxicity re- ductions during acute exposure of fish and invertebrates to pyrethroid in the presence of suspended sediments. Recent ecotoxicological studies have increasingly empha- sized the importance of long-term observations of effects after short-term contamination [19]. However, to our knowledge, no information is available regarding the comparison of aque- ous-phase and sediment-associated, short-term FV exposure with respect to long-term observation of effects. The objective of the present study was to compare aqueous- phase and sediment-associated, 1-h FV exposure of Limne- philus lunatus Curtis, a caddis fly species that is typical of lowland streams [20], to a pyrethroid insecticide (i.e., FV) during a long observation period (240 d) with different eco- toxicological endpoints: emergence success, emergence pat- tern, male:female ratio, dry weight of adults, and production of biomass. Test species and larval stage, exposure time, amount of suspended particles (5 g/L), FV concentrations (0.001- to 1-g/L exposure and 0.2 to 200 g/kg dry wt), and endpoints were chosen to simulate as closely as possible the situation in agricultural streams potentially contaminated via spray drift or runoff. MATERIALS AND METHODS General After short-term contamination (1 h) in glass beakers, the test organisms were transferred to an outdoor, artificial-stream