Zinc in an oligotrophic patagonic lake: response to a natural environmental disaster in low trophic levels

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

Ghent

Conferencia; 18th International Conference on Heavy Metals in the Environment; 2016

Zinc (Zn) is an essential element for life. Despite its importance, the trophodynamics in natural lake systems has been poorly studied, and is unknown in the Patagonian waterbodies. This element reaches the ecosystem from natural sources, such as volcanic eruptions, which are frequent in the study region, releasing Zn to the aquatic environment by ash leaching (Ruggieri et al., 2011). The Puyehue-Cordón Caulle volcanic complex erupted in 2011 affecting the Lake Nahuel Huapi area, especially the Rincón Branch, the nearest lake point to the volcano. This environment is characterized by a zooplanktonic community composed by copepods and cladocerans and their main predator, the forage small fish Galaxias maculatus (Milano et al, 2013; Arcagni et al, 2015). The aim of this study was to analyze the changes in Zn concentrations ([Zn]) in G. maculatus and its prey associated with the impact of the volcanic event. Zooplankton > 200 μm were sampled from a boat by hauling the water column in two depths (90 to 45 m, and 45 m to the surface). G. maculatus adults were captured using baited traps and seine nets. [Zn] were determined by Instrumental Neutron Activation Analysis in lyophilized material (Ribeiro Guevara et al., 2005). The zooplankton studied consists of adult cladocerans Bosmina longirostris (O. F. Müller, 1785), Ceriodaphnia dubia (Richard, 1894) and the copepod Boeckella gracilipes. In the samples collected immediately before the Puyehue-Cordón Caulle 2011 eruption, [Zn] ranged from 85 to 258 μg g-1, whereas after the event (Winter 2011) [Zn] were maximum (29-805 μg g-1), decreasing to 87-156 μg g-1 in 2012 and 2014. G. maculatus [Zn] showed the same trend, increasing considerably after the eruption (285-593 μg g-1) and returning to previous values one year later, (112-191 μg g-1), a condition that remained after 2 years (116-198 μg g-1). Higher Zn concentrations observed in both trophic levels after the volcanic event may be related to a higher input of Zn from the volcanic ashes. However, a year later the system recovered showing similar [Zn] levels than those recorded before the eruption.