Bioaccumulation and transfer of mercury in biofilm, macrophytes and benthic macroinvertebrates in an ultraoligotrophic lake of Northwest Patagonia, Argentina

ARCAGNI, M; RIZZO, A.; CAMPBELL, L.; ARRIBÉRE, M.; KYSER, K; KLASSEN, K.; RIBEIRO GUEVARA, S.

Guiyang, China

Conferencia; 9th International Conference on Mercury as a Global Pollutant; 2009

The objective of this work was to study the accumulation and trophic transfer of mercury in a benthic lower trophic food web using nitrogen stable isotopes in Moreno Lake (41°05´S; 71°32´W; 765 m a.s.l.). This ultraoligotrophic lake is divided in two basins (East (ME) and West (MW)) regarding its geographic position and is located in Nahuel Huapi National Park, Argentina. Mercury concentrations and stable isotope ratios (ä15N, ä13C) were measured in Galaxias maculatus (small puyen), benthic macroinvertebrates (primary and secondary consumers) and primary producers (macrophytes and biofilm). Mercury was measured by Instrumental Neutron Activation Analysis and the stable isotope ratios using an Isotope Ratio Mass Spectrometer. Total mercury (THg) in small puyen ranged from 0.14 to 0.86 ìg.g-1 dry weight (DW) in ME and from 0.11 to 1.27 ìg.g-1 DW in MW, in secondary consumers (predators) ranged from 10 to 59 ìg.g-1 DW in ME and from 0.09 to 2.43 ìg.g-1 DW in MW and in primary consumers (remaining invertebrate taxa) ranged from <0.06 to 3.44 ìg.g-1 DW in ME and from 0.07 to 2.39 ìg.g-1 DW in MW. In biofilm ranged from 0.03 to 5.83 ìg.g-1 DW in ME and 0.14 to 4.78 ìg.g-1 DW in MW and in macrophytes it ranged from <0.05 to 4.72 ìg.g-1 DW and 0.10 to 7.49 ìg.g-1 DW in ME and MW respectively. The ä15N signature increased with trophic level from producers to primary, secondary consumers and fish and mercury concentration decreased with trophic position from producers to fish in both basins. Mean ä15N values in Moreno East were higher in all the groups analyzed than in Moreno West, but THg mean concentrations were higher in Moreno West in all groups but in the primary consumers and small puyen had similar THg concentration. ä13C mean values are higher in small puyen, biofilm and macrophytes and MW than in ME and on the contrary macroinvertebrates (primary and secondary consumers) have lower ä13C values in MW than in ME. No biomagnification or biodilution of mercury was observed in the lower trophic food web within this lake. The variable THg concentrations and ä15N values observed in each basin may be affected by several factors such as lake morphometry, degree of development of the littoral zone, diet and physical and chemical parameters.