Mercury in food webs of Andean Patagonian lakes: dissolved organic matter, bioavailability and bioconcentration potential of pelagic basal organisms

SOTO CÁRDENAS CAROLINA; DIEGUEZ, MARÍA DEL CARMEN; GEREA, MARINA; MARVIN-DIPASQUALE, MARK; RIBEIRO GUEVARA, SERGIO

Granada

Congreso; Aquatic Sciences Meeting 2015. Aquatic Sciences: Global and Regional perspectives- North meets South; 2015

Association for the Sciences of Limnology & Oceanography

Mercury (Hg), a widespread toxic element in aquatic ecosystems, occurs in various chemical forms, transforms dynamically and bioconcentrates throughout foodwebs. In oligotrophic and ultraoligotrophic lakes of Andean Patagonia, the aquatic biota generally bear high total Hg levels. In the pelagic food webs of these lakes, basal organisms (picoplankton) are dominant and incorporate Hg2+, the predominant Hg form, from the dissolved phase making it available to higher trophic levels. Dissolved organic matter (DOM) interacts strongly with Hg, affecting the availability to organisms. In this investigation we experimentally assessed the potential for Hg bioconcentration in the picocyanobacteria Synechococcus, using water from four lakes having a gradient in dissolved organic matter concentration (0.8-3 mg L-1) and quality. Laboratory incubations were performed with 197Hg2+ radiotracer to analyze Hg2+ incorporation by Synechococcus as a function of cellular volume and surface area concentration factors (VCF and SCF). Synechococcus VCF and SCF showed significant negative trends with increasing water color (a440) and the humification index of DOM across all lake water types