Abstract
The hydrological periods drive the structure and organization of aquatic communities in semiarid regions. We hypothesize that a decrease of the precipitation during the dry period will favor the development of the periphytic algal community, leading to higher richness and density in this period. To test this hypothesis, we investigated the changes in the periphytic algal community structure in three shallow and eutrophic ecosystems of the Brazilian semiarid. The sampling was performed between 2007 and 2010 at two-mensal intervals. The sampling of periphytic algal was performed in aquatic macrophytes and rocks. The abiotic variables were analyzed simultaneously. Dominance in diatoms, cyanobacteria and chlorophytes, respectively, was observed in two periods. In the dry period, waters were alkaline and had high concentrations of nitrate and total phosphorus associated with the highest densities of Bacillariophyceae. In the rainy period the water was warmer, oxygenated and high concentrations of ammonia and soluble reactive phosphorus with diatoms remained dominant but with reduced density, while cyanobacteria and chlorophytes increased. Overall, periphytic algal community composition no responded to changes in the hydrological periods. However, the hydrological periods altered the dynamics of periphytic algal community, supported by the alternation of the most representative classes (diatoms and cyanobacteria) between the hydrologic periods. Our data suggest that the morphometric and chemical and physical characteristics of lentic aquatic ecosystems studied were more important in the dynamics of periphytic algal community than the hydrological periods and types of substrates.
Highlights
The periphytic algal community is primarily autotrophic and plays an important role as primary producers in the littoral zone of aquatic ecosystems (Vadeboncoeur and Steinman, 2002; Nozaki et al, 2003)
High electrical conductivity was registered in all reservoirs with higher values during the dry period (6,630 μS.cm-1, n=16), with the exception of Panati pond that showed higher values in the rainy period (622.5 μS.cm-1, n=16)
Our hypothesis that the hydrological period may affect the structure and dynamics in the periphytic algae community was not supported by the data in this study
Summary
The periphytic algal community is primarily autotrophic and plays an important role as primary producers in the littoral zone of aquatic ecosystems (Vadeboncoeur and Steinman, 2002; Nozaki et al, 2003). Algal periphytic acts as excellent bioindicator of water quality and its trophic state (Lobo, 2013). This aspect was emphasized by several researchers (Vercellino and Bicudo, 2006; Bere and Tundisi, 2010; Lobo et al, 2010). The structure and spatial-temporal dynamics of periphytic algal communities in aquatic ecosystems are directly associated to climatic, hydrodynamic and abiotic conditions, as well as specific biological characteristics (Stevenson, 1996; Larned, 2010) and type and quality of the substrate (Rodrigues et al, 2005). The type of substrate, hydrological regime (dry and rainy periods) and amplitude of inter-annual fluctuations in the volume of water have crucial roles in the composition of periphytic algal communities in semiarid aquatic ecosystems
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