Abstract
Despite flagellate protozoa are important for the metabolism of aquatic ecosystems, researches about the ecology of this community is scarce. Therefore, this study investigated the influence of flood regime and hydrological connectivity on the patterns of composition and species richness of protozoan flagellates from aquatic environments in the upper Parana river floodplain. To this end, samplings were undertaken in two periods of the hydrological cycle (March 2008 and September 2008), at six lentic environments associated with the Baia river (three are connected to the river, and three are isolated). 120 taxa were identified in the studied area, distributed in 10 orders and one residual group. This high species richness was sustained by the order Euglenida, which contributed with 70% of total species. The species composition was significantly different between periods and environments, as well as species richness, which was higher in connected environments during the high water period. The results evidenced that the flood pulse and hydrological connectivity are relevant factors driving the structure and dynamic of plankton flagellate protozoa community in the upper Parana river floodplain.
Highlights
The hydrological regime is considered the driving force both for the ecological functioning and for the maintenance of biodiversity patterns in floodplains, since the periodical oscillations of the water flow induce deep changes in the structure and dynamic of the biota (NEIFF, 1990; JUNK et al, 1989).Among the aquatic communities in floodplains, flagellate protozoa play important role in theActa Scientiarum
The faunistic inventory revealed that the community of flagellate protozoa in the studied environments is quite rich, probably due to the relevant contribution of Euglenida order, which contributed with 67% from the total of identified species
The individuals from this order, specially the genera Euglena, Phacus and Trachelomonas, which were the most species-rich in the present study, are commonly found in aquatic environments with high biochemical demand of oxygen, rich in organic matter and ammonia (REYNOLDS et al, 2002). These preferences might have favored the success of these organisms during the high water period due to the great accumulation of allochthonous organic matter (JUNK et al, 1989; LEWIS JR. et al, 2000; NEIFF, 1990)
Summary
The hydrological regime is considered the driving force both for the ecological functioning and for the maintenance of biodiversity patterns in floodplains, since the periodical oscillations of the water flow induce deep changes in the structure and dynamic of the biota (NEIFF, 1990; JUNK et al, 1989).Among the aquatic communities in floodplains, flagellate protozoa play important role in theActa Scientiarum. Biological Sciences energy flow and nutrient cycling (AZAM et al, 1983), because they transfer to the upper trophic levels the energy obtained through the consumption of bacteria, organic detritus, viruses and pico and nanoplanktonic algae (XU et al, 2005) and, contribute significantly for the primary production in the ecosystems (SAFI; HALL, 1997). It is unquestionable the importance of this community to aquatic ecosystems, studies about are still scarce. The effect of the flood regime and the hydrological connectivity on the composition and species richness of flagellate protozoa is not known
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