Influence of a volcanic eruption on potentially toxic elements in the food web from an ultra-oligotrophic Patagonia lake.

ARCAGNI, M.; JUNCOS, R.; RIZZO, A.; CAMPBELL, L.M.; ARRIBÉRE, M.A.; RIBEIRO GUEVARA, S.

Salt Lake City

Encuentro; SETAC North America 36th Annual Meeting; 2015

Volcanoesrepresent a potentially important natural source of elements, such as arsenic(As), bromine (Br), caesium (Cs), mercury (Hg), rubidium (Rb), and selenium(Se) to the atmosphere, where they are transported and deposited in the aquaticsystems. Contents of these elements were analyzed in biota from Lake NahuelHuapi (Argentina) before and after the Puyehue-Cordón Caulle volcanic complexeruption (PCCVC) in 2011, which resulted in pyroclastic material beingdeposited on the lake for several months. Zooplankton, fish and macroinvertebrateswere obtained from three sites from the lake, BR, DH and BL, which haddifferent tephra deposit thickness. Samples were analyzed by INAA in the RA-6research nuclear reactor (CAB-CNEA, Argentina). No general trend was observedin any of the elements analyzed before and after the volcanic eruption withrespect to the organisms or the sites studied. Arsenic contents decreased afterthe eruption in molluscs and Creole Perch in BL and native Small Puyen from DH,but no differences were observed in the rest of the organisms and sites. Brtended to decrease after the eruption, as in the case of Brown Trout and SmallPuyen from BR and BL; however it increased in molluscs from BR. In BR and BL, Csdecreased in molluscs and Small Puyen but increased in insect larvae. Ingeneral, Hg contents remained constant after the eruption, however theydecreased in insect larvae and molluscs from BL and increased in Brown Troutand crustacean from BR. Rb contents were higher in Small Puyen from DH afterthe eruption, but lower in the same species from BL and BR. Se was the onlyelement that increased after the eruption (e.g., Small Puyen from the threesites, or insect larvae from BL and BR) or remained constant. As no clearpattern was observed before and after the eruption in any of the elements byorganism or site, it is difficult to draw conclusions regarding the behavior ofeach element. Variations in the contents of the elements analyzed after theeruption may be caused by changes in the food web structure produced by thetephra deposition with the consequent alteration of the trophodynamic of theelements. The lack of variation in the elemental concentrations, which was observedin most of the cases, may be due to an adaptation of the organisms to a cyclinginput of elements to the system as volcanic eruptions in the area are notuncommon (e.g., PCCVC recent eruptions were in 1960, 1929-1930, and 1919-1930).