Influence of dissolved organic matter character on mercury incorporation by planktonic organisms: an experimental study using oligotrophic water from Patagonian lakes.
Ligands present in dissolved organic matter (DOM) form complexes with inorganic divalent mercury (Hg2+) affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg2+ (the prevailing mercury species in the water column of these lakes) by the algae Cryptomonas erosa and the zooplankters Brachionus calyciflorus and Boeckella antiqua. Hg2+ accumulation was studied through laboratory experiments using natural water of four oligotrophic Patagonian lakes amended witht'97Hg2+. The bioavailability of Hg2+ was affected by the concentration and character of DOM. The entrance of Hg2+ into pelagic food webs occurs mostly through passive and active accumulation. The incorporation of Hg2+ by Cryptomonas, up to 27% of the Hg2+ amended, was found to be rapid and dominated by passive adsorption, and was greatest when low molecular weight compounds with protein-like or small phenolic signatures prevailed in the DOM. Conversely, high molecular weight compounds with a humic or fulvic signature kept Hg2+ in the dissolved phase, resulting in the lowest Hg2+ accumulation in this algae. In Brachionus and Boeckella the direct incorporation of Hg from the aqueous phase was up to 3% of the Hg2+ amended. The dietary incorporation of Hg2+ by Boeckella exceeded the direct absorption of this metal in natural water, and was remarkably similar to the Hg2+ adsorbed in their prey. Overall, DOM concentration and character affected the adsorption of Hg2+ by algae through competitive binding, while the incorporation of Hg2+ into the zooplankton was dominated by trophic or dietary transfer.
Laboratorio de Fotobiología, INIBIOMA CONICET-UNComahue, Quintral 1250, Bariloche, Argentina. dieguezmc@gmail.com
María C
MC
Diéguez
Laboratorio de Fotobiología, INIBIOMA CONICET-UNComahue, Quintral 1250, Bariloche, Argentina.
Claudia P
CP
Queimaliños
Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Bustillo km 9.5, 8400 Bariloche, Argentina.
Sergio Ribeiro
SR
Guevara
United States Geological Survey, 345 Middlefield Rd./MS 480, Menlo Park, CA 94025, USA.
Mark
M
Marvin-DiPasquale
Laboratorio de Fotobiología, INIBIOMA CONICET-UNComahue, Quintral 1250, Bariloche, Argentina.
Carolina Soto
CS
Cárdenas
Laboratorio de Análisis por Activación Neutrónica, Centro Atómico Bariloche, CNEA, Bustillo km 9.5, 8400 Bariloche, Argentina.
María A
MA
Arribére
D000818:Animals; D001118:Argentina; D033342:Copepoda / Q000378:metabolism*; D044785:Cryptophyta / Q000378:metabolism*; D060106:Lakes / Q000737:chemistry*; D008628:Mercury / Q000737:chemistry / Q000378:metabolism*; D010933:Plankton / Q000378:metabolism*; D012403:Rotifera / Q000378:metabolism*
D008628:Mercury