Trophic transfer of zinc in the food chains of native and non-native predator fish from a northern Patagonian oligotrophic lake

MONTAÑEZ, J.C.; RIZZO, A.; JUNCOS, R.; ARCAGNI, M.; ARRIB¨¦RE, M.A.; CAMPBELL, L.M.; RIBEIRO GUEVARA, S.

Buenos Aires

Encuentro; SETAC Latin America 11th Biennial Meeting; 2015

Zinc (Zn)is an essential element that is carefully regulated by physiological mechanismsin most organisms. Thus, bioaccumulation of Zn and its flow through food websshould not be analyzed and interpreted in the same context as non-essentialelements. In aquatic systems, food is often the major exposure route of metalsto animals. In this sense, the aim of this work was to assess the trophictransfer of Zinc, in simplified food chains of introduced and native fish toppredators, in the northernmost area of Lake Nahuel Huapi, the largestoligotrophic system in North Patagonia Andean Range, Argentina. Zincconcentrations [Zn] and stable nitrogen isotopes (d15N) were determined inthree plankton fractions (P1: 10-50 ¦Ìm, P2: 50-200 ¦Ìm,P3: >200 ¦Ìm), in aplanktivorous native fish (the small puyen Galaxias maculatus), in a benthiccrayfish (Samastacus spinifrons), in two introduced salmonids (rainbow troutOncorhynchus mykiss and brown trout Salmo trutta) and in a native fish (creoleperch Percichthys trucha). Samples were obtained at Brazo Rinc¨®n in Lake NahuelHuapi. Zinc concentrations were determined by Instrumental Neutron ActivationAnalysis and d15N, as an estimator of trophic level, were assessed by IsotopeRatio Mass Spectrometry. To describe trophic transfer patterns of Zn in thefood chains of predator fish (salmonids and creole perch), the relationshipbetween d15N and log10-transformed [Zn] was analyzed for each sampled item. Thehighest [Zn] were recorded in pelagic primary producers (P1) ranging from 960to 5070 ¦Ìg g-1 dryweight (DW) and in rotifers and mixotrophic ciliates (P2, 187-2712 ¦Ìg g-1 DW), followed by G. maculatus(176-432 ¦Ìg g-1 DW),cladocerans and copepods (P3, 85-258 ¦Ìg g-1 DW), and S. spinifrons (68.4-174 ¦Ìg g-1 DW). Lower [Zn] were recorded in toppredator fish. The native creole perch showed [Zn] between 20 and 92 ¦Ìg g-1 DW, while the lowest [Zn] werefound in salmonid muscle, ranging from 12 to 18 ¦Ìg g-1 DW for O. mykiss, and 12.3 to 18.2 ¦Ìg g-1 DW for S. trutta. A decreasein [Zn] from lower to higher trophic levels was observed.