Preliminary examination of food web structure of Nicola Lake (Taim Hydrological System, south Brazil) using dual C and N stable isotope analyses

Abstract

Taim Ecological Reserve is located within the Taim Hydrological System and was created to protect a heterogeneous and productive landscape harboring exceptional biological diversity in southern Brazil. Using stable isotope ratio analyses of carbon (δ 13 C) and nitrogen (δ 15 N), we provide a preliminary description of the food web structure, including estimates of production sources supporting fish populations and vertical trophic structure, within a representative lake of this system. A total of 21 organisms (5 macrophytes, 3 mollusks and 13 adult fishes) representing 16 species were collected for isotope analysis. Fishes had δ (-25.49 to -27.10 ‰), and suggesting that these plants could be a major carbon source supporting these fishes. δ 13 C signatures of Corbicula (-30.81‰) and Pomacea (-24.26‰) indirectly suggest that phytoplankton and benthic algae could be alternative carbon sources for some consumers. Nitrogen isotope ratios indicated approximately three consumer trophic levels. The pearl cichlid Geophagus brasiliensis was a primary consumer. Two catfishes (Trachelyopterus lucenai and Loricariichthys anus) were secondary consumers. Two congeneric pike cichclids (Crenicichla lepidota and C. punctata), a catfish (Pimelodus maculatus) and the characids Astyanax fasciatus and Oligosarcus robustus were tertiary consumers. Further studies including additional primary producers and consumers and greater sample numbers should be conducted to provide a more complete and detailed description of food web structure and dynamics within the reserve.A Estação Ecológica do Taim está inserida dentro do Sistema Hidrológico do Taim e foi criada para proteger uma região heterogênea e produtiva no sul do Brasil, abrigando uma diversidade biológica excepcional. A partir da análise de isótopos estáveis do carbono (δ 13 C) e nitrogênio (δ 15 N), esse trabalho fornece uma descrição preliminar da estrutura da teia alimentar numa lagoa representativa desse sistema, incluindo estimativas dos produtores primários que sustentam suas populações de peixes e a estrutura trófica vertical. Um total de 21 organismos (5 macrófitas, 3 moluscos e 13 peixes adultos), representando 16 espécies, foram coletados para a análise da composição isotópica. Os peixes tiveram valores de δ 13 C variando entre -24.30 ‰ e -28.31 ‰, com uma amplitude de variação concordante com as macrófitas (-25.49 e -27.10 ‰), sugerindo indiretamente que essas plantas poderiam ser uma fonte de carbono importante para os peixes. As assinaturas δ 13 C de Corbicula (-30.81‰) e Pomacea (-24.26‰) sugerem que fitoplâncton e algas bentônicas podem ser outra fonte de carbono para alguns consumidores. As razões isotópicas do nitrogênio indicaram aproximadamente três níveis tróficos de consumidores. O cará Geophagus brasiliensis foi um consumidor primário, enquanto o penharol Trachelyopterus lucenai e o cascudo-viola Loricariichthys anus foram consumidores secundários. Duas espécies congenéricas de joaninha (Crenicichla lepidota e C. punctata), o pintado Pimelodus maculatus, o lam...

Trophic relationships between macroinvertebrates and fish in a pampean lowland stream (Argentina)

“…The values for δ 15 N were over 9‰ and were usually higher than the data reported by other authors for the Neotropical Region (Wantzen et al, 2002;García et al, 2006;Molina et al, 2011). These higher values would indicate that the macroinvertebrates analyzed here were omnivorous, with only P. joaquini being a predator.…”

Trophic ecology of Arapaima in Guyana: giant omnivores in Neotropical floodplains

“…Stable isotope analyses have the advantage of providing an integrative perspective on recent feeding habits without having to sacrifice large numbers of individuals over time for stomach analyses (e.g., Melville & Connolly, 2003;Garcia et al, 2006). Our results taken as a whole (i.e., isotope values, morphology and diets) suggest that Guyanese Arapaima are more appropriately considered omnivores rather than top predators.…”

“…An alternative method to assess time-integrated, assimilated diet is to analyze stable isotope ratios of an organism's tissues (Melville & Connolly, 2003;Garcia et al, 2006). Stable isotopes of nitrogen become enriched in the heavier isotope as they move to higher levels within a food web, and they are generally used as an indicator of trophic position (Peterson & Fry, 1987;Kelly, 2000;Post, 2002).…”

Hydrodynamic Control of Plankton Spatial and Temporal Heterogeneity in Subtropical Shallow Lakes

“…This lake is surrounded by a variety of habitats including dunes, pinus forests, grasslands, and two wetlands. This heterogeneous landscape harbors an exceptional biological diversity, which motivated the Brazilian federal authorities to protect part of the entire hydrological system as the Taim Ecological Station in 1991 (Garcia et al, 2006). The watershed (ca.…”