The effects of arsenic speciation on accumulation and toxicity of dietborne arsenic exposures to rainbow trout

Abstract

The effects on juvenile rainbow trout survival, growth, food consumption, and food conversion efficiency from dietborne exposures to inorganic arsenic (arsenite, arsenate) and to the organoarsenicals monomethylarsonate (MMA), dimethylarsinate (DMA), and arsenobetaine (AsB) were investigated in two experiments: (1) a 28-d exposure using a live diet of oligochaete worms separately exposed via water to these five arsenic compounds and (2) a 56-d exposure using a pellet diet prepared from commercial fish food to which arsenite, MMA, or DMA were added. In the live diet experiment, the degree to which worms could be contaminated with the organoarsenicals was limited by toxicity to the worms and other experimental constraints, so that their toxicity relative to inorganic arsenic could not be fully established, but AsB was concluded to have low toxicity, consistent with published results for mammals. For the pellet diet experiment, MMA and DMA were found to be at least an order of magnitude less toxic than inorganic As on the basis of concentration in the diet, as well as much less toxic on the basis of accumulation in the fish. The need to consider speciation in aquatic risk assessments for arsenic was further demonstrated by tissue analyses of three macroinvertebrate species from a mining-impacted stream, which showed large variations in both total arsenic and the relative amounts of inorganic and organic arsenic. Additionally, although effects of arsenic on trout appear to be well correlated with inorganic arsenic, worms were found to be more sensitive to waterborne DMA than to inorganic arsenic, showing that low toxicity of organoarsenicals cannot be assumed for all aquatic organisms. Various difficulties in evaluating and applying studies on dietborne exposures and fish growth are also discussed.

Biodilution of Organic Species of Arsenic in Freshwater Food Webs

“…[DMA] in invertebrates ranged from 0.006 to 1.266 mg/kg dry weight (Supporting Information, Figure SI-5c) and were less than the MDL in only two samples (two crayfish: one Ramsey, one Johnnie). These concentrations are generally higher than those previously reported in benthic invertebrates (0.06 mg/kg dry wt; Erickson et al, 2019) and zooplankton (0.08-0.15 mg/kg dry wt; Caumette et al, 2011) from mining-impacted areas.…”

“…Organisms can also uptake arsenic from their prey into the intestines through dietary exposure (Pei et al, 2019). The relative importance of each uptake pathway can vary among taxa, with some being more sensitive to waterborne exposure than dietary, or vice versa (Erickson et al, 2011(Erickson et al, , 2019. Absorbed arsenic then enters the bloodstream and is distributed through the body.…”

“…Furthermore, much of the available literature on AsB formation in freshwater organisms comes from laboratory exposures rather than natural systems (Caumette et al, 2012). From the existing literature on freshwater environments, there appears to be considerable variation in arsenic speciation profiles in invertebrates and fish, when compared with marine systems (Byeon et al, 2021;Caumette et al, 2012Caumette et al, , 2014Erickson et al, 2019;Kaise et al, 1997;Lepage, 2023;Miyashita et al, 2009). The drivers of this variation are unclear, but it may be a result of differences in water chemistry, including arsenic concentrations or speciation, which have been shown to alter arsenic speciation in freshwater plankton (Caumette et al, 2014) and fish (Lu et al, 2023).…”

Arsenic bioaccumulation in subarctic fishes of a mine-impacted bay on Great Slave Lake, Northwest Territories, Canada

“…The assimilation efficiency of dietary arsenic and its retention in fish tissues is low, resulting in rapid efflux rates [6, 9, 10]. Arsenic speciation in the diet affects the degree of toxicity to fish, with inorganic arsenic having higher toxicity than some organoarsenicals [11]. In addition, fish species vary in their capacity to metabolize inorganic arsenic and transform it into more benign organic species [12].…”

Toxicological effects of As (V) in juvenile rockfish Sebastes schlegelii by a combined metabolomic and proteomic approach

“…The toxicity of As to organisms depends on its species. Generally, the inorganic forms of As are the most toxic forms in marine ecosystems (Erickson et al, 2019). Among the inorganic forms, arsenate (As (V)) is the dominant form in natural waters.…”