Abstract
The hydrological condition of floodplain systems alters the structure and dynamic of aquatic communities. We suggest that the structure of zooplankton community changes according to the flood phases and connectivity. This study was carried out in a floodplain lake located in the Northern Pantanal (Brazil). Zooplankton density varied considerably over time, although the sampling stations presented similar densities. The densities ranged from 2,000 ind. M-3 in the high water phase to more than 2,300,000 ind. M-3 during the low water phase when the lake remains isolated. The densities of the groups also presented a temporal variation. Rotifers described the community mainly in the low water phase and microcrustaceans during the high water phase. Variations in the total zooplankton and groups densities were significantly correlated to the PCA 1 axis (negatively composed by water depth and positively by turbidity) and to the food availability (phytoplankton).
Highlights
The hydrological conditions of river-floodplain systems alters the dynamic of the biota, leading the inhabiting organisms to develop several modifications, such as population size and the ability to colonize new habitats, changing the structure of the aquatic communities in these environments (JUNK et al, 1989; NEIFF, 1990).The zooplankton community, in freshwater environments, is mainly represented by Rotifera, Cladocera and Copepoda; these organisms play an important role in the energy flow and nutrient cyclingActa Scientiarum
Many authors have argued the influence of the water level on the structure and dynamic of the zooplankton in the floodplains from the Amazon basin (ROBERTSON; HARDY, 1984; BOZELLI, 1994) and from the upper Paraná river (SENDACZ, 1997; LANSAC-TÔHA et al, 2004; BONECKER et al, 2005)
From the prediction that the flood and the connectivity are the main responsible for the changes in the habitat and, in the communities, three flood phases were determined according to the water level variations of Cuiabá river and Coqueiro lake, and the connection between the lake and the river channel: phase I; phase II; and phase III
Summary
The hydrological conditions of river-floodplain systems alters the dynamic of the biota, leading the inhabiting organisms to develop several modifications, such as population size and the ability to colonize new habitats, changing the structure of the aquatic communities in these environments (JUNK et al, 1989; NEIFF, 1990).The zooplankton community, in freshwater environments, is mainly represented by Rotifera, Cladocera and Copepoda; these organisms play an important role in the energy flow and nutrient cyclingActa Scientiarum. Many authors have argued the influence of the water level on the structure and dynamic of the zooplankton in the floodplains from the Amazon basin (ROBERTSON; HARDY, 1984; BOZELLI, 1994) and from the upper Paraná river (SENDACZ, 1997; LANSAC-TÔHA et al, 2004; BONECKER et al, 2005). These studies have shown that the flood regime changes directly (e.g., dilution effect)
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