Effect of sediment‐associated pyrethroids, fipronil, and metabolites on Chironomus tentans growth rate, body mass, condition index, immobilization, and survival

Abstract

Pyrethroids and fipronil insecticides partition to sediment and organic matter in aquatic systems and may pose a risk to organisms that use these matrices. It has been suggested that bioavailability of sediment-sorbed pesticides is reduced, but data on toxicity of sediment-associated pesticides for pyrethroids and fipronil are limited. In the current study, 10-d sediment exposures were conducted with larval Chironomus tentans for bifenthrin, lambda-cyhalothrin, permethrin, fipronil, fipronil-sulfide, and fipronil-sulfone, the last two being common fipronil metabolites. Sublethal endpoints included immobilization, instantaneous growth rate (IGR), body condition index, and growth estimated by ash-free dry mass (AFDM). Pyrethroid lethal concentrations to 50% of the population (LC50s) were 6.2, 2.8, and 24.5 microg/g of organic carbon (OC) for bifenthrin, lambda-cyhalothrin, and permethrin, respectively; with the former two lower than previously published estimates. Fipronil, fipronil-sulfide, and fipronil-sulfone LC50 values were 0.13, 0.16, and 0.12 microg/g of OC, respectively. Ratios of LC50s to sublethal endpoints (immobilization, IGR, and AFDM) ranged from 0.90 to 9.03. The effects on growth observed in the present study are important because of the unique dipteran life cycle involving pupation and emergence events. Growth inhibition would likely lead to ecological impacts similar to mortality (no emergence and thus not reproductively viable) but at concentrations up to 4.3 times lower than the LC50 for some compounds. In addition, C. tentans was highly sensitive to fipronil and metabolites, suggesting that dipterans may be important for estimating risk and understanding effects of phenylpyrazole-class insecticides on benthic macroinvertebrate communities.

Addition of contaminant bioavailability and species susceptibility to a sediment toxicity assessment: Application in an urban stream in China

“…(1)). The LC50 values were taken from the literature (Amweg et al, 2006;Ding et al, 2010Ding et al, , 2011Hintzen et al, 2009;Maul et al, 2008;Maund et al, 2002). Concentration addition was recommended for predicting mixture toxicity of pesticides (Belden et al, 2007), thus summation of TUs of individual contaminants was used to assess the mixture toxicity in sediment.…”

Chronic Toxicity Thresholds for Sediment-Associated Benzo[a]pyrene in the Midge (Chironomus dilutus)

“…Immobile midges, when pinched with a pair of forceps, were considered dead. In addition, growth of the midges was also determined by ash free dry mass (AFDM) measurements according to the method presented by Maul et al (2008). Briefly, the surviving organisms were placed in preweighed aluminum pans and dried at 60°C for 3 days to obtain mean mass per organism.…”

“…For example, concentrations of BaP in sediments from the Pearl River Delta in China ranged from 0.111 to 18.3 lg/g OC (Mehler et al 2011b), suggesting possible chronic sublethal toxicity in some sites. The decrease of their growth and emergence could negatively affect the population of the midges (Maul et al 2008). Thus, the application of chronic toxicity thresholds for predicting longterm sublethal effects may also provide a better understanding of the impact of PAHs in sediment at the population level.…”

Pyrethroid Insecticides: Use, Environmental Fate, and Ecotoxicology

“…Although not tested, these reductions in growth are likely to affect later size and fecundity. Maul et al (2008a) noted that pyrethroid-mediated reductions in growth had later effects on Chironomid fitness. Both larval ash free dry mass (AFDM) and instantaneous growth rate (IGR) were negatively impacted by exposure to sediment contaminated with bifenthrin, lambda-cyhalothrin, or permethrin, with respective 10-day LOAECs of 2.2, 2.0 and 74.2 µg/g OC.…”