Competition of Cladocerans for Natural Seston from a Tropical Shallow Lake

Abstract

The planktonic cladocerans Ceriodaphnia richardi, Daphnia gessneri, and Daphnia birgei inhabit the limnetic and littoral zones of Lake Monte Alegre, where the former species tends to be abundant. Laboratory experiments were carried out to investigate the competition for seston of the limnetic and littoral zones in cladocerans using life table data. In experiment 1, the species C. richardi and D. gessneri were fed seston from the limnetic zone (1–1.29 mg C L−1); in experiment 2, the species C. richardi and D. birgei were fed seston from the littoral zone. Despite the relatively high concentration of sestonic algae (0.96–1 mg C L−1), with predominance of nanoplankton, C. richardi outcompeted D. gessneri in the experiment with the limnetic seston. The species C. richardi and D. birgei benefited from the presence of each other in the experiment with littoral seston, where nanoplankton predominated, with increases in some parameters of the life table. D. birgei, however, showed better reproductive performance than C. richardi. A comparison between the results of the experiments suggests that the seston of the limnetic zone, in terms of quantity and quality, is better for C. richardi than the littoral seston.