Abstract
Abstract Drought events will become more frequent due the climate change. In floodplains, periphytic algae are responsible for part of the primary production, are the principal source of organic carbon deposition, play an important role in mineralization and nutrient cycling, and are the base of the food web for many organisms. As algae distribution in aquatic environments is a strong indicator of physical and chemical conditions of the sites, we aimed to determine the structure of periphytic algae in lentic and lotic environments during drought conditions and to uncover the main local abiotic factors in community structuring. We hypothesized diatoms would be more frequent than green algae and desmids at both sites, due to their resistance characteristics, and that higher periphyton algal richness, density and diversity would occur in the lake due to the greater availability of nutrients and the absence of flow. The study was carried out in the Finado Raimundo lake and the Ivinhema river in the Upper Paraná river floodplain during the low water period of 2011. Petioles of the aquatic macrophyte Eichhornia azurea (Sw.) Kunth were used as a substrate for periphytic algae. We found a total of 171 species, 104 species in the lake and 80 in the river. Diatoms were predominant at both sites due to their strategic traits, and between sites, there were different patterns in the periphytic algal community structure, owing to the distinctive physical and chemical characteristics of the lake and the river. Achnanthidium minutissimum (Kützing) Czarnecki and Nitzschia palea (Kützing) W. Smith were the most abundant species in both environments. Our results showed patterns of periphytic algae in a floodplain during drought conditions, which will assist in understanding their structuring during future drought scenarios.
Highlights
Floodplains are among the most productive ecosystems on the planet and represent major centres of biological diversity (Junk 1996)
The lake was more influenced by dissolved oxygen (DO) and NH4+, whereas the river was most influenced by dissolved solids, conductivity and PO4++ (Table 1)
This study demonstrated that in low water levels, diatoms are predominant in both sites
Summary
Floodplains are among the most productive ecosystems on the planet and represent major centres of biological diversity (Junk 1996). The Upper Paraná river floodplain is the last remaining wetland area of the Paraná River that is not dammed in Brazil (Agostinho 1997, Gois et al 2015) This area has high habitat diversity, which endows it with unique limnological characteristics that allows conservation of high species diversity (Thomaz et al 1997, Thomaz et al 2007). The presence of reservoirs upstream of the Upper Paraná river (approximately 35 dams) controls the hydrological regime, influencing nutrient cycling, and the structure and composition of communities within this system (Agostinho et al 2000, 2008, 2009, Stevaux et al 2009, Souza-Filho et al 2010) Flood periods in these areas have been found to have reduced frequency, duration, and intensity, increasing the periods of low water and drought in these environments (Souza-Filho 2009). It is expected that global drought events would be more frequent in the near future due to climate change and decreases in precipitation (Barnett et al 2005, Woodwand et al 2010)
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