Abstract
Benthic periphytic biofilms are important food sources at the base of aquatic ecosystems. These biofilms also sit at the interface of oxic waters and hypoxic sediments, and can be influenced by, or influence trace element speciation. Here we compared arsenic enrichment in periphyton exposed to arsenate [As(V)] or arsenite [As(III)] (20 ug/L, static renewal, 7 days), and we found similar accumulation patterns of total As (101 ± 27 and 88 ± 22 mg kg−1 dw, respectively). Periphyton As was 6281- and 6684-fold, higher than their aqueous exposures and occurred primarily as As(V). When these biofilms were fed to larval mayflies, similar total arsenic tissue concentrations (13.9 and 14.6 mg kg−1 dw, respectively) were observed, revealing significant biodilution (approximately 10% of their dietary concentrations). Finally, we investigated the influence of aeration and periphyton presence on arsenic speciation in solutions treated with As(III). Predominantly As(III) solutions were slowly oxidized over 7 days, in the absence of periphyton, and aeration did not strongly affect oxidation rates. However, in the presence of periphyton, solution chemistry showed rapid As(III) oxidation to As(V) and an increasing proportion of organo-As forming over time. Thus, periphyton plays several roles in arsenic environmental behavior: 1) decreasing total dissolved As concentrations via abiotic and biotic accumulation, 2) rapidly oxidizing As(III) to As(V), 3) effluxing organo-arsenic forms into solution, and 4) limiting trophic transfer to aquatic grazers. This article is protected by copyright. All rights reserved
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