Zinc concentrations in the food web of a Northern Patagonian oligotrophic lake

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

Córdoba

Congreso; VI Congreso Argentino de la Sociedad de Toxicología y Química Ambiental; 2016

Zinc (Zn) is an essential element that is carefully regulated by physiological mechanisms in most organisms. In aquatic systems, food is often the major exposure route of metals, including Zn, to animals. The recruitment, retention and bioaccumulation of trace metals are also affected by physical factors, such as lake size, basin area and water chemistry as well as ecological factors: trophic position, growth rate, age and food web structure.Northern Patagonia is a region characterized by a great diversity of watersheds and glacial ultraoligotrophic lakes. Due to its isolations and low population density this area has been protected from direct anthropogenic contamination. Furthermore, the National Park system provided protection for many of the watersheds.In this sense, the aim of this work was to determine the concentrations of Zn in the most representative food web organisms of Lake Nahuel Huapi, considering that Patagonia aquatic systems are poorly studied for trace elements contents.Zinc concentrations were determined (in muscle, liver, hepatopancreas or whole body) by Instrumental Neutron Activation Analysis in: three plankton fractions (P1: 10-50 µm, P2: 50-200 µm, P3: > 200 µm); benthic decapods Samastacus spinifrons and Aegla sp.; the amphipod Hyalella curvispina; the molluscs Diplodon chilensis and Chilina sp.; insect larvae; two introduced salmonids (rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta) and the native fish Percichthys trucha (creole perch), Olivaichthys viedmensis (velvet catfish), Galaxias platei (big puyen) and Galaxias maculatus (small puyen). Samples were obtained in three sites in Lake Nahuel Huapi.The highest Zn were recorded in pelagic primary producers (P1, 225-5070 µg g-1 DW) followed by mixed plankton (P2, 187-2712 µg g-1 DW) and then zooplankton (P3, 85-314 µg g-1 DW).In the benthic habitat, Zn concentrations were as follows: insect larvae (140-330 µg g-1 DW) > Aegla sp. (95-308 µg g-1 DW) > S. spinifrons (68-303 µg g-1 DW) > Diplodon sp. (90-153 µg g-1 DW) > Chilina sp. (63-117 µg g-1 DW).Zinc concentrations in fish, from higher to lower were: G. maculatus (122-432 µg g-1 DW) > O. viedmensis (25-115 µg g-1 DW) > G. platei (37-74 µg g-1 DW) > P. trucha (17-110 µg g-1 DW) > O. mykiss (12-42 µg g-1 DW) > S. trutta (12-18 µg g-1 DW). The lowest Zn were recorded in top predator fish.These results might suggest that the greater the physiological, histological and phylogenetic complexity, the higher the regulatory capacity of this element.