Inorganic mercury uptake by plankton in oligotrophic lakes of Patagonia (Argentina): does the quality of dissolved organic carbon matter?

DIÉGUEZ, MARÍA DEL CARMEN; RIBEIRO GUEVARA, SERGIO; QUEIMALIÑOS CLAUDIA P.; MARVIN-DIPASQUALE, MARK; SOTO CÁRDENAS, CAROLINA; ARRIBÉRE, MARÍA A.

Gdansk

Conferencia; 15th International Conference on Heavy Metals in the Environment; 2010

Chemical Faculty, Gdansk University of Technology (GUT) Committee on Analytical Chemistry of the Polish Academy of Sciences (PAS)

The concentration and quality of dissolved organic carbon (DOC) have been implied as factors controlling the transformation of inorganic mercury (Hg2+) to organic Hg in Andean lakes (Patagonia, Argentina). In the current study, we further hypothesize that DOC also partially controls Hg2+ uptake into the plankton in these environments as well. This project goal was to analyse the effect of DOC quality on the uptake of Hg2+ by algae and zooplankton in waters from Lakes Moreno, Morenito, El Trébol and Escondido, which represent a gradient in DOC quality and concentration. A series of experiments simultaneously assessed DOC quality via fluorescence spectrometry, and Hg2+ bioaccumulation in the algae Crytomonas erosa, the rotifer Brachionus calyciflorus and the calanoid copepod Boeckella antiqua. Bioaccumulation was evaluated by adding radioisotopically enriched 197Hg2+ into flasks containing the various lake waters (pre-filtered through 0.2 µm) with the organisms. After incubating for 24 hours in darkness, 197Hg specific activity was measured in the organisms recovered from the water. The uptake of Hg2+ by pelagic organisms was found to be highly variable as a function of the natural DOC gradient. The use of killed controls also suggested that the passive Hg2+ uptake appears as the dominant mechanism in the accumulation of Hg2+ from the environment by live algae. In herbivorous zooplankton, the highest uptake of Hg2+ was found to be dietary while the passive uptake of dissolved Hg2+ was almost negligible.