Silver accumulation in chironomid larvae in relation to their ecological in an ultraoligotrophic lake

WILLIAMS, N.; RIZZO, A.; AÑÓN SUÁREZ, D.; RIBEIRO GUEVARA, S.; ARRIBÉRE, M.A.

Ghent

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

We carried out a seasonal study of Ag concentrations ([Ag]) in chironomid larvae inhabiting different substrates in Lake Moreno Oeste (Patagonia, Argentina), in order to evaluate a relationship between their ecological preferences (substrate, feeding habits) and metal concentration. This is a key aspect on Ag trophodynamics, given that sediments are a storage site for heavy metals in lake systems, and chironomids may act as a doorway organism to lake trophic webs. Chironomid larvae were collected seasonally from different substrates in two bays in Lake Moreno Oeste between March 2014 and February 2015. Selected substrates were: the macrophyte Myriophyllum sp., sediment under submerged (Myriophyllum sp. and Nitella sp.) and emergent macrophytes (Schoenoplectus californicus), stones and sediment at 4 and 20 m deep. [Ag] in larvae were determined by Instrumental Neutron Activation Analysis (INAA). Higher [Ag] were recorded in larvae inhabiting Myriophyllum sp. (Fig.1). Submerged plants can accumulate large amounts of pollutants (Pokorny et al., 2015) and transfer them to insects feeding on them. [Ag] recorded in larvae taken from the sediment under the macrophytes were also high (Fig.1), possibly related with the ability of plants to accumulate Ag principally in their root systems (Rate, 1999), affecting larvae living and feeding there. The lower [Ag] recorded in larvae belonging to the subfamily Tanypodinae could be associated with the predatory habits of this group (Ashe et al., 1987). Although [Ag] recorded in larvae inhabiting sediment at 20 m depth during autumn and winter were low, [Ag] during spring and summer were notably higher (Fig.1). This may be related with the increase in metabolic rate associated with higher temperatures (Nichols & Playle, 2004). The spatial and temporal distributions of chironomid larvae and their feeding habits affect [Ag] bioaccumulation. This information should be considered in trophodynamic studies in lake trophic webs.