Biotransformation of dichlorodiphenyltrichloroethane in the benthic polychaete, Nereis succinea: Quantitative estimation by analyzing the partitioning of chemicals between gut fluid and lipid

Abstract

Biotransformation plays an important role in the bioaccumulation and toxicity of a chemical in biota. Dichlorodiphenyltrichloroethane (DDT) commonly co-occurs with its metabolites (dichlorodiphenyldichloroethane [DDD] and dichlorodiphenyldichloroethylene [DDE]), in the environment; thus it is a challenge to accurately quantify the biotransformation rates of DDT and distinguish the sources of the accumulated metabolites in an organism. The present study describes a method developed to quantitatively analyze the biotransformation of p,p'-DDT in the benthic polychaete, Nereis succinea. The lugworms were exposed to sediments spiked with DDT at various concentrations for 28 d. Degradation of DDT to DDD and DDE occurred in sediments during the aging period, and approximately two-thirds of the DDT remained in the sediment. To calculate the biotransformation rates, residues of individual compounds measured in the bioaccumulation testing (after biotransformation) were compared with residues predicted by analyzing the partitioning of the parent and metabolite compounds between gut fluid and tissue lipid (before biotransformation). The results suggest that sediment ingestion rates decreased when DDT concentrations in sediment increased. Extensive biotransformation of DDT occurred in N. succinea, with 86% of DDT being metabolized to DDD and <2% being transformed to DDE. Of the DDD that accumulated in the lugworms, approximately 70% was the result of DDT biotransformation, and the remaining 30% was from direct uptake of sediment-associated DDD. In addition, the biotransformation was not dependent on bulk sediment concentrations, but rather on bioaccessible concentrations of the chemicals in sediment, which were quantified by gut fluid extraction. The newly established method improved the accuracy of prediction of the bioaccumulation and toxicity of DDTs.

Gut Microbial Profiles in Nereis succinea and Their Contribution to the Degradation of Organic Pollutants

“…To more accurately assess sediment risk, many efforts have been made to understand the biotransformation process of xenobiotics in organisms, which is of great importance in chemical bioaccumulation, biomagnification, and toxicity. Wang et al found most DDT transformed to DDD (86%) and DDE (2%) in the benthic polychaete Nereis succinea which considerably changed the composition of bioaccumulative DDT and its transformation products. Recent studies found mercury methylation and demethylation in fish intestine and gut microbial activities were suspected as the driving force, yet there was no direct evidence. , Furthermore, a current-use insecticide, fipronil, was metabolized at similar rates in liver and intestine, implying probable degradation of fipronil by the intestinal microbiota .…”

Full–Life Cycle Toxicity Assessment of Sediment‐Bound DDT and Its Degradation Products on Chironomus dilutus

“…The concentrations of DDT continued to decrease during the toxicity testing. Although DDT is regarded as a persistent organic pollutant, fast degradation of DDT in freshly spiked sediments has also been commonly reported (Hoke et al ; Lotufo et al ; Ding et al ; Wang et al ). As a result, the organisms were actually exposed to a mixture of DDT, DDD, and DDE in the present study.…”

“…The extraction was conducted for 3 cycles of 5 min each, with temperature being set at 80 °C and pressure at 1500 psi. The extracts were concentrated by a gentle flow of nitrogen and solvent exchanged to 1 mL of hexane and purified using concentrated H 2 SO 4 (Wang et al 2015). Briefly, 1 mL of concentrated H 2 SO 4 was added to the extracts, and the solution was shaken for 3 min and centrifuged at 2000 rpm for 5 min.…”

Spatio-temporal trends and body size differences of OCPs and PCBs in Laeonereis culveri (Polychaeta: Nereididae) from Southwest Atlantic estuaries

“…Moreover, the DDD predominance observed in L. culveri tissues is in agreement with the results in N. succinea. The high metabolic capacity to transform DDT in DDD (> 86%) and direct uptake from the sediment would account for this high DDD accumulation in polychaete tissues (Wang et al, 2015). In addition, it could be also related to high excretion and/or avoidance capability to ingest toxic forms of DDTs in sediments (Lotufo et al, 2000;Wang et al, 2015).…”

“…The high metabolic capacity to transform DDT in DDD (> 86%) and direct uptake from the sediment would account for this high DDD accumulation in polychaete tissues (Wang et al, 2015). In addition, it could be also related to high excretion and/or avoidance capability to ingest toxic forms of DDTs in sediments (Lotufo et al, 2000;Wang et al, 2015). Moreover, the predominance of DDD in SWA estuarine sediments suggests higher DDT dechlorination to DDD under anaerobic conditions due to the characteristics of these muddy sand sediments (Lin et al, 2009).…”