Ecotoxicology of arsenic in the marine environment

Abstract

Arsenic has a complex marine biogeochemistry that has important implications for its toxicity to marine organisms and their consumers, including humans. The average concentration of total arsenic in the ocean is about 1.7 μg/L, about two orders of magnitude higher than the U.S Environmental Protection Agency's human health criterion (fish consumption) value of 0.0175 μg/L. The dominant form of arsenic in oxygenated marine and brackish waters is arsenate (As V). The more toxic and potentially carcinogenic arsenite (As III) rarely accounts for more than 20% of total arsenic in seawater. Uncontaminated marine sediments contain from 5 to about 40 μg/g dry weight total arsenic. Arsenate dominates in oxidized sediments and is associated primarily with iron oxyhydroxides. In reducing marine sediments, arsenate is reduced to arsenite and is associated primarily with sulfide minerals. Marine algae accumulate arsenate from seawater, reduce it to arsenite, and then oxidize the arsenite to a large number of organoarsenic compounds. The algae release arsenite, methylarsonic acid, and dimethylarsinic acid to seawater. Dissolved arsenite and arsenate are more toxic to marine phytoplankton than to marine invertebrates and fish. This may be due to the fact that marine animals have a limited ability to bioconcentrate inorganic arsenic from seawater but can bioaccumulate organoarsenic compounds from their food. Tissues of marine invertebrates and fish contain high concentrations of arsenic, usually in the range of about 1 to 100 μg/g dry weight, most of it in the form of organoarsenic compounds, particularly arsenobetaine. Organoarsenic compounds are bioaccumulated by human consumers of seafood products, but the arsenic is excreted rapidly, mostly as organoarsenic compounds. Arsenobetaine, the most abundant organoarsenic compound in seafoods, is not toxic or carcinogenic to mammals. Little of the organoarsenic accumulated by humans from seafood is converted to toxic inorganic arsenite. Therefore, marine arsenic represents a low risk to human consumers of fishery products.

Proteomic and metabolomic responses in D-shape larval mussels Mytilus galloprovincialis exposed to cadmium and arsenic

“…Although Cd is relatively rare in marine environment, the concentration of Cd has reached 50 mg/L in some heavily polluted estuaries or harbors and ports [4]. In open ocean seawater, the concentration of total arsenic is usually around 1 mg/L and As (V) is the dominant form of inorganic arsenic [5].…”

Comparative investigations on the biological effects of As (III) and As (V) in clam Ruditapes philippinarum using multiple biomarkers

“…After acclimation, the clams were randomly divided into three tanks (control, arsenite (NaAsO 2 , As (III)) and arsenate (NaHAsO 4 , As (V)) exposures) containing eight individual clams in 20 L aerated seawater. The experimental concentration of As (V) was set at 20 mg/L that was environmental relevant [4,20]. The environmental concentration of As (III) is usually around 10% of that As (V).…”

“…In aquatic environment, arsenic may occur in different chemical forms, including inorganic forms of arsenite (As (III)) and arsenate (As (V)) and organic forms such as arsenoribosides, arsenobetaine, monomethylarsonic acid and dimethylarsinic acid [3]. In open ocean seawater, the concentration of total arsenic is usually around 1e3 mg/L [4].…”

“…In addition, As (III) is about 60 times more toxic than As (V) to human body. The concentration of As (V) is usually higher than that of As (III) in seawater, however, the concentration of As (III) is still approximately 13% of the concentration of arsenate in the seawater along the coast [4]. Due to the higher toxicity of As (III) than As (V), the biological effects of As (III) should not be ignored.…”

Biological Oxidation of Arsenite in Strong Acid Water

“…Arsenic occurs mostly as arsenite (As (III)) or arsenate (As (V)) in natural water. As(III) is more toxic than As(V) 1) , and As(V) is removed more effectively than As(III) by the conventional treatment processes 2) . Some mine drainages, hot spring waters and ground waters contain arsenic.…”