Interactions with DOM and biofilms affect the fate and bioavailability of insecticides to invertebrate grazers

Abstract

We studied the fate and bioavailability of insecticides in short-term experiments (48 h) with different hydrophobicity (3.8 pM carbofuran, 3.0 pM lindane, and 5.3 pM chlorpyrifos) across gradients in dissolved organic matter (low-, medium-, and high-DOM) in freshwater microcosms, mimicking runoff events of pesticides. The effects of biofilms were studied by including treatments with biofilms cultivated under different DOM-concentrations. The presence of biofilms negatively affected chlorpyrifos water concentrations, indicating rapid sorption of this hydrophobic pesticide, while lindane concentrations instead increased and carbofuran concentrations were unaffected. Associations of lindane and chlorpyrifos with biofilms were 1.6-2.0 times higher in low- and high-DOM than in medium-DOM treatments, indicating that sorption was affected not only by the quantity, but also by the quality of DOM. Although the proportion of pesticides recovered in biofilms was consistently less than 1 % of added pesticide, pesticide concentrations in biofilms were on average more than 75- (carbofuran) and 382-times (lindane) higher than those in water. Snail accumulation of all three pesticides was significantly affected by DOM-concentrations and correlated to pesticide hydrophobicity, but the relationships were not straightforward. For example, carbofuran uptake in treatments without biofilms was higher in low-DOM than in medium- and high-DOM treatments, while chlorpyrifos uptake instead increased across the DOM-gradient. Biofilms played a role only for the uptake of chlorpyrifos, which decreased markedly in the presence of biofilms. Bioconcentration factors (BCF) calculated for snails and biofilms differed for the three pesticides and were related to their sorption behaviour (i.e., hydrophobicity). The relative proportion of pesticide uptake through biofilm consumption was consistently less than 2 %, showing that passive uptake was by far the predominant uptake pathway for all three pesticides.

Microbial Extracellular Polymeric Substances (EPSs) in Ocean Systems

“…When animals ingest the matrix, coincidentally during their feeding on sediments, cells or flocs, they will consume the sorbed metals and organics as well. EPS have been shown to be an efficient trophic-transfer vehicle for sorbed metals in amphipods (Schlekat et al, 1998, 1999, 2000; Selck et al, 1999), and organic compounds such as pesticides, although most of the latter work has even been conducted in freshwater systems (Widenfalk et al, 2008; Lundqvist et al, 2010, 2012). …”

Comparison of specific versus literature species sensitivity distributions for herbicides risk assessment

“…First, phytobenthos is embedded in an exopolysaccharides matrix that interacts with water constituents and could adsorb hydrophobic chemicals (Wolfaardt et al 1994;Headley et al 1998;Lundqvist et al 2012). As a result, benthic growth in biofilm could modify the exposition of organisms to herbicides and their sensitivity Larras et al 2013).…”

A novel method to assess effects of chemical stressors on natural biofilm structure and function

“…Due to the prevalent indirect and direct effects of primary producers (Fleeger, Carman & Nisbet, 2003;Clements & Rohr, 2009;Clements, Hickey & Kidd, 2012), additional assays can be conducted to explore how chemical exposure alters biofilm interactions with both consumers and abiotic ecosystem compartments. Finally, biofilms readily sorb many pollutants (Lock et al, 1984;Lundqvist, Bertilsson & Goedkoop, 2012), and chemical analysis of biofilms can provide an estimate of potential dietary exposure to consumers. Different endpoints can vary greatly in how they respond to chemical stress; for example, at low concentrations of dissolved metals, taxon richness may decline but primary production and biomass increase (Niyogi, Lewis & McKnight, 2002).…”