Bioconcentration of benzo[a]pyrene in Chironomus riparius and Lumbriculus variegatus in relation to dissolved organic matter and biotransformation

Abstract

The relative health of benthic invertebrate populations is threatened by both dissolved and strongly-bound contaminants. Sediment-bound contaminants can be mobilized and metabolized in the guts of deposit-feeders and may lead to even more potent derivatives. For this reason, measures of parent substance concentrations in organisms are not a suitable exposure indicator when substantial biotransformation can occur. In this study, we assessed the concentration of waterborne 14C-benzo[a]pyrene (BaP) in Chironomus riparius larvae and in the oligochaete Lumbriculus variegatus at different levels of dissolved organic carbon (DOC). These two species have different biotransformation capabilities. Polydimethylsiloxane (PDMS) fiber was used to assess the freely-dissolved concentrations for the prediction of uptake and elimination kinetics. Exposure concentrations decreased due to the presence of DOC. Radioactivity that corresponded to the metabolites exceeded 90% of total extractable fractions in C. riparius, and suggested that BaP metabolism was faster than uptake from solution. However, only 10% of the extracted activity was attributed to metabolites in L. variegatus. Measured tissue concentrations and model-predicted uptake and elimination rates showed that L. variegatus mainly accumulated parent compound, whereas C. riparius accumulated mainly metabolites. No effect of DOC was observed on the biotransformation of BaP in either species.

Assessing the toxicity of the “inert” safener benoxacor toward Chironomus riparius: Effects of agrochemical mixtures

“…This reduction in biotransformation and the activity of major detoxification enzymes may interfere with detoxification of other environmental contaminants (e.g., chlorpyrifos) and increase susceptibility to toxicants . Chironomus riparius is capable of rapid biotransformation of a variety of organic contaminants, including chlorophenols, pyrenes, and the herbicide trifluralin , which should limit bioaccumulation; however, these metabolites may be toxic. Because S ‐metolachlor and benoxacor share similar physical/chemical properties (Table ), it is possible that the combined effect of S ‐metolachlor and benoxacor on the production of detoxification enzymes may explain their synergistic effects.…”

A Reduced Model for Bioconcentration and Biotransformation of Neutral Organic Compounds in Midge

“…Active feeding or unlimited food access are usually absent in midge bioaccumulation studies. Typical practices in midge studies are passive feeding of dissolved organic matter naturally present in environmental waters (Agbo et al 2013) and sediment (Maund et al 2002), or no feeding at all (Metcalf et al 1973;Artola-Garicano et al 2003;Widenfalk et al 2008). Such practices avoid the need to account for growth effect and minimize the potential interference of unconsumed food particles to reduce chemical bioavailability (i.e., lowering freely dissolved fraction) to the organism.…”

“…Variable temperature may be necessary to reflect different field thermal conditions and varying optimal temperatures for individual invertebrates. The presence of solids/ substrates may be needed to support attachment (Agbo et al 2013), promote survival (Kuperman et al 2016), or prevent cannibalism (Weston et al 2009) in invertebrates. Re-examining some of these criteria for bioaccumulation data seems sensible and necessary for invertebrates that have been underinvestigated (e.g., midge).…”

“…The use of midge in bioconcentration characterization is especially appealing. Because of its very small body size (i.e., microgram range), both the uptake and the depuration periods can be very short, such as a few days (Simkiss et al 2001; Harwood et al 2009; Agbo et al 2013) or even a few hours (Gerould et al 1983; Chen et al 2016). Study of the internal distribution and dynamics (Yohannes et al 2017; Hou et al 2019) of contaminants between different organs and tissues can also be neglected in the midge for the same reason, thus simplifying the interpretation of kinetics.…”

“…The same criteria need not be always applicable. With small invertebrates, chemical uptake can be accomplished literally in a beaker or jar (Weston et al 2009; Agbo et al 2013), and a strict flow‐through set‐up may not be needed for exposure constancy. Variable temperature may be necessary to reflect different field thermal conditions and varying optimal temperatures for individual invertebrates.…”