Short-term variability of copepod abundance in Jurumirim Reservoir, São Paulo, Brazil

Abstract

Short-term variability in composition and abundance of copepod populations were studied during the dry (winter) and rainy (summer) seasons, at the dam region of Jurumirim Reservoir, São Paulo, Brazil. An intensive sampling program was carried out during 30 days in each period of the year. Samples and measurements were taken every other day at 0, 5, 10, 15, 20 and 25 m depths. The relationship between variability of the populations and some environmental factors was analyzed. The main species were: Argyrodiaptomus furcatus (Sars), Notodiaptomus iheringi (Wright), Mesocyclops longisetus (Thiébaud), Thermocyclops decipiens (Fischer), and T. minutus (Lowndes). Thermocyclops minutus was the most abundant species in dry season and its abundance varied significantly between sampling days. A large increase in abundance of calanoids occurred during the rainy season. This increase was correlated with higher temperature values. At that time, Notodiaptomus iheringi was dominant. This species showed significant short-term variations in abundance in both dry and rainy seasons. Significant variation in density of populations within the same sampling period might result from either the dispersion pattern of the populations or continuous substitution of the water masses. Significant correlation was observed between copepod abundance and temperature, especially for species of calanoids and there was also some correlations between densities of particular species of copepods and some phytoplankton taxa, mainly during the dry season. As for vertical distribution, most organisms were found between the surface and 15 m deep. During the rainy season, there was some evidence of the occurrence of spatial segregation between species of cyclopoids and calanoids, with the cyclopoids in a deeper position within the water column.

Longitudinal distribution of Copepoda populations in the transition zone of Paranapanema river and Jurumirim Reservoir (São Paulo, Brazil) and interchange with two lateral lakes

“…In the other hand, Velho et al (2001) found only one calanoid (Notodiaptomus iheringi) in 21 sampling stations along the Corumbá Reservoir, including the river (upstream and downstream from the dam), tributaries, and lateral arms. In this study, Notodiaptomus iheringi reached small densities although it was frequent and, attained high densities in the lacustrine zone of Jurumirim Reservoir (Nogueira & Panarelli, 1997;Panarelli et al, 2001;Nogueira, 2001). Cyclopoids were represented by Mesocyclops and Thermocyclops, the latter genus being the most abundant.…”

Zooplankton fluctuations in Jurumirim Reservoir (São Paulo, Brazil): a three-year study

“…Coincidence in major abundance peaks of these species was not observed, indicating a temporal segregation between them. As observed by Panarelli et al (2001), T. minutus (Lowndes, 1934) was more abundant in the dry period.…”

“…In terms of temporal dynamics, the monthly variation of the thermal regime and stability, oxygen deficit (Henry 1992(Henry , 1993a) and primary production by phytoplankton (Henry, 1993b;Henry et al, 2006); the influence of hydrological seasonality on seston sedimentation and transport (Henry and Maricato, 1996); the space-temporal variation of phytoplankton (Henry et al, 1998), zooplankton (Nogueira, 2001), and physical-chemical variables , have all been analyzed. Shorter periods of time have also been considered for zooplankton studies in Jurumirim: short term (weekly) variability in rainy and dry periods (Panarelli et al, 2001) and vertical migration in nictemeral cycles (Nogueira and Panarelli, 1997). Some interdecade information (70's and 80's) on the composition and abundance of zooplankton has also been provided (Sampaio et al, 2002).…”

Zooplanktonic community of six reservoirs in northeast Brazil

“…In Brazil, the most studied reservoir ecosystems are located in the Southeast, South and West regions, such as the Paranoá in Brasilia, Pampulha in Minas Gerais, Monte Alegre and Jurumirim in São Paulo and Segredo in Paraná. Many studies have been carried out in these regions on the composition and diversity of zooplankton, especially concerning the Rotifera and Crustacea (Cabianca and Sendacz, 1985;MatsumuraTundisi et al, 1990;Arcifa et al, 1998;Güntzel and Rocha, 1998;Nogueira, 2001;Panarelli et al, 2001;Mitsuka and Henry, 2002).…”