ELEVATED ARSENIC CONCENTRATIONS IN HOT SPRINGS CREEK, AKUTAN ISLAND, ALEUTIAN ISLANDS: A NATURAL LAB TO STUDY POINT-SOURCE POLLUTION OF THE COASTAL OCEAN

Up to eight large hydrothermal springs are discharging into Hot Springs Creek, Akutan Island. The springs are located more than one half kilometer away from Hot Springs Bay and the Bering Sea. Reaching temperatures as high as 99.7º C and pH as low as 5.9, hot spring fluids contain average arsenic concentrations of 743 mg/l, with a maximum of 1240 mg/l. A recent analysis of arsenic abundance in Hot Springs Creek water at the point of discharge into Hot Springs Bay revealed average concentrations of 47 mg/l. Comparatively, 5 streams within the same valley which are not affected by hydrothermal venting averaged 0.85 mg/l arsenic. Seawater in Hot Springs Bay averaged 2.05 mg/l As. In addition to increased total arsenic concentration, there are also relatively higher concentrations of the AsIII oxidation state, which is considered much more toxic and more mobile than AsV. Flux measurements indicate that up to 7.5 kg As per day are being discharged into the coastal marine environment of Hot Springs Bay.

Shallow, near-shore marine environments are key spawning, feeding and growing areas for many organisms. In the Bering Sea, these waters are important for commercially important fish species, because there juveniles seek protection prior to migration into deeper water. While in the coastal environment, these juvenile fish are also the food source for many birds and mammals. The chemistry of these coastal waters is typically controlled by ocean circulation, groundwater discharge, rainfall and/or runoff. However, in areas of volcanic activity, such as the Aleutians, the presence of near-shore hydrothermal activity can introduce potentially toxic elements, such as arsenic (As). Thus, the potential for bioaccumulation of toxic metals up the food-chain in Aleutian Islands can be very high.