The role of predation in the diel vertical migration of zooplankton in two tropical freshwaters ecosystems (original) (raw)

Aim: This study aimed to examine and compare the different patterns of diel vertical migration (DVM) in two tropical freshwater ecosystems: Carioca Lake (PERD, MG), dominated by piscivorous fishes and Nado reservoir (Belo Horizonte, MG), dominated by planktivorous/omnivorous fishes. Methods: The vertical distribution of the zooplankton was examined at noon and midnight, in April 2003 in both systems, using a Schindler-Patalas trap. Results: In Nado reservoir, the larvae of the invertebrate predator Chaoborus, remained in the hypolimnion during the day and ascended into the surface waters at night. The same migratory behavior was observed for the population of the copepod Thermocyclops inversus, the dominant zooplankter, as well as for the rotifers. In Carioca Lake, the Chaoborus larvae did not migrate, and individuals were found occupying the entire water column in daytime as well as at night. The population of the copepod T. minutus, a potential prey of Chaoborus larvae, and most rotifers also did not migrate in Carioca Lake. Conclusions: In Nado reservoir, where planktivorous and omnivorous fishes dominate, the zooplankton was forced to adopt the diurnal vertical migration (DVM), a phenomenon that propagated through the different trophic levels. In Carioca Lake, in the virtual absence of vertebrate predators of zooplankton, no migration in the planktonic community was observed.