Spatial variation in the stable isotopes of 13C and 15N and trophic position of Leporinus friderici (Characiformes, Anostomidae) in Corumbá Reservoir, Brazil

Alexandre L Pereira,Cássia M Sakuragui,Evanilde Benedito

doi:10.1590/s0001-37652007000100006

Alexandre L Pereira, Cássia M Sakuragui + Show 1 more

Open Access

https://doi.org/10.1590/s0001-37652007000100006

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Abstract

Stable isotopes of carbon (delta13C) and nitrogen (delta15N) were used to describe sources of energy and trophic position for adult Leporinus friderici in the area of the Corumbá Reservoir, Brazil. Samples were collected from April 1999 to March 2000. Spatial variations were not identified in the isotopic composition. The maximum and minimum contribution of C4 plants calculated integrating the variation of plants and fish were 47.7% and 2.4%, respectively. Among C3 plants, periphyton presented closer isotopic values to those observed for fishes, corresponding to an important carbon source. The proportion of ingested plant item is larger in rivers upstream from the reservoir (42.7%), which justifies the smaller trophic level among there. However, in the reservoir, the ingestion of fish was 81.4%, while ingested plants contributed with 18.6%. Downstream from the dam, participation of plant item was even smaller (14.4%). Although the trophic position calculated with diet data was proportional to the one calculated with delta15N values, the former elevated the trophic level of L. friderici in the food web, because estimated trophic positions were based on fish items belonging to the 2nd (a) and to the 3rd (b) trophic levels.

Highlights

The use of stable isotopes of carbon (δ13C) and nitrogen (δ15N) has been intensified in the last years (Hobson and Wassenaar 1999)
Considering the results presented in Fry and Sherr (1984) for food webs of aquatic communities, the isotopic composition of phytoplankton was established through zooplankton with 1◦/◦◦ fractionation per trophic level
Trophic position (TP) based on δ15N was calculated according to formula (Vander Zanden et al 1997): TP = δ15Nfish − 5.7 + 1 3.4 where: δ15Nfish = mean value of δ15N for L. friderici; 5.7 = average δ15N for vascular plants; 3.4 = increase of trophic level for δ15N

Summary

INTRODUCTION

The use of stable isotopes of carbon (δ13C) and nitrogen (δ15N) has been intensified in the last years (Hobson and Wassenaar 1999). Ecological studies with Leporinus friderici were conducted in the Brazilian stretch of Paraná River without dams (Andrian et al 1994, Vazzoler et al 1997), in Itaipu Reservoir (Agostinho et al 1992, BeneditoCecilio et al 1997) and in the dammed stretch of the basin (Lopes et al 2000, Benedito-Cecilio et al 2005). These studies generated valuable information to support management actions. Our hypothesis is that the variations of δ13C and δ15N are specific for each area of the reservoir and, equivalent to the composition of the food ingested by the species

MATERIALS AND METHODS

RESULTS AND DISCUSSION

Plants