Origem e destino do carbono em sistemas límnicos – uso de técnicas isotópicas em reservatórios e lagos rasos

Abstract

The stable isotopes technique is a tool that overcame in many aspects the methods originally applied on element cycle studies. Therefore it has been largely used in limnologic researches. This work has focused effort on two investigation lines based on isotopic ecology: (1) estimation of carbon sources and spatial patterns of suspended matter in tropical reservoirs and (2) evaluation of carbon flow through food web components on South American shallow lakes. The terrestrial influence over reservoirs seston showed a wide variation range (from 7 to 100%). It was strongly related to the systems zonation and was considered a factor of discerning between them. The patterns on isotopic composition observed in the shallow lakes were not related to the latitude gradient. In general, the 13C-depleted primary producers (δ13C between -33 e 22‰) presented higher importance as energetic basis to consumers. The aims of this study were attained, complementing the results reached by the projects it takes part: Balanço de Carbono nos Reservatórios de FURNAS Centrais Elétricas S.A., that is focused on evaluating the potential of green house gasses emissions from reservoirs, and South American Lake Gradient Analysis, that aims to verify the effects of climate changes on shallow lakes dynamics.