TITLE:
Dynamics of Cladocera Community in a Tropical Hypereutrophic Environment (Garças Reservoir, São Paulo, Brazil)
AUTHORS:
Ariane Carolina Di Genaro, Suzana Sendacz, Munique de Almeida Bispo Moraes, Cacilda Thais Janson Mercante
KEYWORDS:
Eutrophycation, Zooplankton, Cladocerans, Bosmina, Tropical Reservoir
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.7 No.5,
March
25,
2015
ABSTRACT: This
study was performed at Garcas Reservoir, a hypereutrophic urban lake within Sao
Paulo metropolitan area, Southeast Brazil. This reservoir underwent to a marked
limnological change after the harvest of free floating macrophytes, shifting to
a hypereutrophic state. Present purposes were to characterize the Cladocera
community and verify its association with the water deterioration after the
macrophytes removal period as well as to compare it to previous studies, before
macrophytes harvesting. Samplings were collected from October 2007 until
September 2008 and the results were compared to data obtained during
pre-removal period (1997). Principal Component Analysis (PCA) showed that the
highest values for water transparency were associated with the macrophytes
pre-removal period while the highest values of electrical conductivity,
chlorophyll a and total phosphorus
were associated with the macrophytes post-removal period, indicating the
degradation of the water quality. During this period, large cladocerans
disappeared and the small sized species of Bosmina predominated. Male organisms of this genus were found as well as elevated
densities of Bosmina huaroensis,
suggesting overcrowding. Furthermore, it was detected a reduction of 82% in the
number of species compared to data from 1997. The shifts to the hypereutrophic
state led to aggressive alterations in Cladocera community, suggesting a strong
stress on populations.