PM02 Metals in the Environment: Aquatic Biological Perspectives
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM057) Arsenate Uptake by a Freshwater Cyanobacterium.
Markley, C1, Herbert, B1, 1 Texas A&M University, College Station, Texas, United States
ABSTRACT- It is commonly accepted that the presence of oxy-hydroxides (iron and manganese) are the dominant factor controlling the fate and transport of arsenic in surface waters; data now suggest that organoarsenicals are major components controlling arsenic fate and transport in geologic environments with limited oxy-hydroxides. Elevated arsenic levels are common in South Texas from both natural (weathering of As-containing units) and anthropogenic sources (a byproduct from decades of uranium mining). Sediment samples collected from South Texas show highly variable reactive iron concentrations, virtually undetectable in many areas. These results suggest that oxy-hydroxide controls on arsenic are unlikely, thus leaving another mechanism to control arsenic speciation and the resultant bioavailability. Although studies have shown that eukaryotic algae isolated from arsenic contaminated waters have an increased tolerance to arsenate and the ability to uptake arsenate, a freshwater cyanobacterium, Anabaena sp. PCC 7120, never previously exposed to arsenate, can effectively utilize arsenate in phosphate-limited conditions. Preliminary experiments using the cyanobacterium, Anabaena sp. PCC 7120, showed arsenate uptake and increased cell replication when exposed to high arsenate concentrations. Additional experiments measured arsenate uptake over time to determine the kinetics of trace metal uptake. Future experiments will explore arsenate uptake in the presence of phosphate, a potentially competitive inhibitor. These results may indicate that biologic conversion of arsenic and other trace metals into organic species may be an important trace metal sink that is overlooked in South Texas.
Key words: bioavailability, arsenic, cyanobacteria