Biomethylation and biotransformation of arsenic in a freshwater food chain: Green alga (chlorella vulgaris)→shrimp (neocaridina denticulata)→killifish (oryzias iatipes)

Abstract

Tolerance, bioaccumulation, biotransformation and excretion of arsenic compounds by the freshwater shrimp (Neocaridina denticulata) and the killifish (Oryzius latipes) (collected from the natural environment) were investigated. Tolerances (LC,,) of the shrimp against disodium arsenate [abbreviated as As(V)], methylarsonic acid (MAA), dimethylarsinic acid (DMAA), and arsenobetaine (AB) were 1.5, 10, 40, and 15Opg As ml-I, respectively. N . denticulata accumulated arsenic from an aqueous phase containing 1 pg As ml-' of As(V), 10 pg As ml-' of MAA, 30 pg As ml-' of DMAA or 150 pg As ml-' of AB, and biotransformed and excreted part of these species. Both methylation and demethylation of the arsenicals were observed in oiuo. When living N. denticulata accumulating arsenic was transferred into an arsenic-free medium, a part of the accumulated arsenic was excreted. The concentration of methylated arsenicals relative to total arsenic was higher in the excrement than in the organism.Total arsenic accumulation in each species via food in the food chain Green algae (Chlorella oulgaris) +shrimp (N.denticulatu) -+killifish (0. lafipes) decreased by one order of magnitude or more, and the concentration of methylated arsenic relative to total arsenic accumulated increased successively with elevation in the trophic level. Only trace amounts of monomethylarsenic species were detected in the shrimp and fish tested. Dimethylarsenic species in alga and shrimp, and trimethylarsenic species in killifish, were the predominant methylated arsenic species, respectively.

Mercury and Arsenic Bioaccumulation and Eutrophication in Baiyangdian Lake, China

“…These results are consistent with previous studies that have also documented a biodiminution of As in aquatic food webs [Maeda, 1994;Chen and Folt, 2000]. This may be the result of relatively high levels of As excretion relative to assimilation in freshwater organisms [Maeda et al, 1992;Kuroiwa et al, 1994;Suhendrayatna et al, 2002]. Arsenic concentrations in zooplankton and in fish across sites also decreased with increasing 13 C suggesting that more pelagic pathways of carbon resulted in higher As bioaccumulation in biota [France, 1995].…”

Arsenic Compounds in Higher Fungi

“…However, the fate of arsenic in terrestrial ecosystems is still largely unknown. Except for some studies on arsenic species in freshwater food chains, 1,2 freshwater algae, 3 and fish, 4 only a few papers have been published about arsenic species in terrestrial plants such as vegetables, 5 moulds 6 and mushrooms. 7,8 Arsenobetaine and arsenocholine have been identified in the terrestrial environment thus far only in mushrooms.…”

Speciation of Metals and Metalloids in Biological Systems

“…Their findings point to the role of S-adenosylmethionine, or a related sulfonium compound as possible methyl donors. Arsenic biomethylation and biotransformation has also been demonstrated in a freshwater environment (Kuroiwa et al, 1994). Byrne et al (1995), in a study of arsenic-accumulating mycorrhizal and saprophytic mushrooms, identified and confirmed the presence of methylarsonic acid, arsenite, arsenate, dimethylarsinic acid and arsenobetaine.…”