Foodweb dynamics affect arsenic speciation and bioaccumulation in lakes affected by gold mines

Abstract

We investigated the bioaccumulation patterns of arsenic species in freshwater food webs from three lakes near historical mining operations in the Northwest Territories, Canada. Two of these lakes (Long Lake and Lower Martin Lake) were located within 5 km of the mine's roaster stacks, while a third lake (Small Lake), situated 27 km away, served as a far-field reference site. In each lake, we measured the concentrations of arsenic species, including As(III), As(V), MMA, DMA and organic arsenobetaine, AsB, across multiple environmental and biological compartments, including water, sediment, macrophytes, periphyton, phytoplankton, zooplankton, benthic invertebrates, and small- and large-bodied fish. Across all lakes, total arsenic and inorganic arsenic (As(III) and As(V)) concentrations were inversely related to an organism's trophic position as determined by δ¹⁵N. This trend likely reflects the biotransformation of inorganic arsenic to AsB within tissues as well as increased dietary intake of AsB-rich prey, which facilitates As elimination. Our findings suggest that trophic position is a key determinant of inorganic arsenic bioaccumulation, explaining 39–89% of inorganic As bioaccumulation.