The trophic role of zooplankton in a floodplain lake of Colombian amazon, through stable isotopes analysis

In order to characterize the primary sources of carbon for zooplankton and its flow in the food web in a lake of flooding near the town of Leticia (Amazonas, Colombia), collections of bacteria, detritus, phytoplankton, periphyton and zooplankton were conducted between May 2010 and February 2011. Zooplankton was used as an integrator for its central position in the food web and was analyzed in terms of delta(13)(C) and delta(15)(C) the organisms collected in 60 mu m mesh, represented by Cladocera, Copepoda Ciclopoida and Rotifera. The samples were concentrated with GF/F pre burned filters for laboratory analysis of stable isotopes in the UNESP in Botucatu (SP). delta(13)(C) values show a poor trophic relationship between zooplankton (-37.99% +/- 2.14) and its potential sources such as phytoplankton (-32.53% +/- 1.97), periphyton (-32.56% +/- 1 55) and detritus (-32.27 % +/- 0,81). Moreover, although zooplankton d15N values (6.12% +/- 0.59) complement the assessment of phytoplankton (7.38% +/- 1.1), they suggest depleted periphyton consumption (1.15 % +/- 0.07) and detritus (5.23% +/- 4,76). d13C impoverished values are associated with the consumption of a methanogenic carbon fraction, which has been demonstrated in the hypolimnion of floodplain lakes in the same way as their contribution to the upper layers of the water column during mixing events. This specialization of zooplankton in consuming a fraction of several trophic guilds can be the result of the intrinsic variability of resources as a result of biogeochemical changes associated with the hydrology of the lake.