Metabolization of emamectin benzoate into desmethyl emamectin benzoate in spiked marine sediments

• Published in: Chemosphere (Oxford) 2023-02, Vol.313, p.137635, Article 137635
• Main Authors: Hamoutene, D., Gagnon, M., Davies, J., Le, A., Black, M., Blais, D.R., Kingsbury, M.
• Format: Article
• Language: English
• Subjects: Animals; Antiparasitic Agents; Aquaculture; Copepoda; Emamectin benzoate; Geologic Sediments; Ivermectin; Metabolites; Sediments
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.137635

Emamectin benzoate (EMB) (4″deoxy- 4″-epi-methylaminoavermectin) is a pesticide developed to control pests on various crops, and in forestry. It is also used in salmon aquaculture to control sea lice infestations as an in-feed therapeutant. Little is known about EMB metabolites and potential associated toxicities in marine sediments. In this study, we used natural marine sediments (sand and mud) fortified at an EMB concentration of 60 ppb (wet weight). Results show an almost immediate transformation of EMB to Desmethyl EMB (DES) with no increased rates of metabolization when stored sediment samples were incubated for up to 16 h. The transformation ratio of EMB to DES represented between 0.16 and 0.39% of EMB; values are lower than what has been observed in fish tissue. Data suggest that DES is generated through both abiotic (tested after autoclaving marine sediments) and biological processes. Further work on freshly sampled marine sediments with EMB deposits, different organic regimes, and a detailed assessment of active bacterial communities are necessary to better evaluate the EMB to DES rate of transformation around aquaculture sites. [Display omitted] •Emamectin benzoate (EMB) is used in salmon aquaculture to control sea lice infestations.•Natural marine sediments spiked with EMB were used for this study.•Results show a transformation of EMB to Desmethyl EMB (DES) at a EMB/DES rate close to 0.4%.•Data suggest that DES is generated through both abiotic and biological processes.