ECOTOXICOLOGY OF ARSENIC IN THE MARINE ENVIRONMENT—Review

Abstract

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 g/L, about two orders of magnitude higher than the U.S Environmental Protection Agency's human health criterion (fish consumption) value of 0.0175 g/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 g/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 g/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.

Interannual patterns of variation in concentrations of trace elements in arms of Octopus vulgaris

“…The mechanism of this transformation is, however, not clear (Bettencourt, 1990). The dominant form of arsenic in oxygenated marine and brackish waters is arsenate, which is very toxic (Neff, 1996).…”

Arsenic speciation in polychaetes (Annelida) and sediments from the intertidal mudflat of Sundarban mangrove wetland, India

“…Little of the organoAs accumulated by humans from seafood is converted to toxic As III and therefore marine As represents a low risk to humans (Maher et al, 2011). In contrast, As V is the most toxic of the arsenic species found in environmental samples (Neff, 1997); its presence as a significant arsenic species in polychaetes suggests that these organisms may have a particular resistance to As V , or metabolises it in a unique manner. The third point of interest is the presence of DMA and PO 4 -arsenoriboside as the most dominant organoarsenicals.…”

Radionuclides, Metals, and Hydrocarbons in Oil and Gas Operational Discharges and Environmental Samples Associated with Offshore Production Facilities on the Texas/Louisiana Continental Shelf with an Environmental Assessment of Metals and Hydrocarbons.

“…Arsenic concentrations in ambient seawater range from 0.64 Fg/L at VR 214A (nearshore) to 1.6 Fg/L at HI A-595CF (offshore). Open ocean waters may contain up to 3 Fg/L arsenic (Neff, 1996b).…”

“…This variability in concentrations of arsenic in tissues of marine animals may be related to the forms and concentrations of arsenic in ambient seawater and the diet and the ability of different marine animals to sequester, metabolize, or excrete accumulated inorganic and organic arsenic. Marine micro-and macro-algae can bioaccumulate dissolved arsenate (the dominant form of arsenic in seawater) from seawater and convert it to organic forms that are sequestered in the tissues (Neff, 1996b). Marine animals that consume the algae bioaccumulate large amounts of arsenic, particularly the organic forms.…”

“…Many marine animals have tissue residues of arsenic that exceed current screening concentrations, most of which were developed for freshwater animals. Most of the arsenic in the tissues of marine animals is in the form of various nontoxic organo-arsenic compounds, particularly arsenobetaine (Neff, 1996b). The organo-arsenic compounds are not harmful to the marine animals themselves or their consumers.…”