Periphytic algae of the Garças Lake, Upper Paraná River floodplain: comparing the years 1994 and 2004.

The changes imposed by dams on hydrological regime, water transparence and nutrient concentrations downstream affect biodiversity in relation to species richness and specific composition of the community. The aim of this work was evaluate this effect on periphyton, comparing richness and composition of periphytic algae in the Garças Lake, Upper Paraná River floodplain, between the years 1994, before construction of the Porto Primavera Reservoir, and after its operation in 2004. This floodplain lake showed an increase in species, from 113 in 1994 to 159 in 2004. A few species, however, were common during the last year, dominated by Zygnemaphyceae and some Bacillariophyceae species. The increase in algal diversity in 2004 may be the result of the ability of the system to adapt to environmental changes. However, the large change in the periphyton species composition suggests further impacts on the food web, demanding continuity of long-term studies in order to determine their consequences on the biodiversity as a whole.

Effects of hydrological regime and connectivity on the interannual variation in taxonomic similarity of periphytic algae.

The aim of this study was to analyze the effects of flood pulses (intensity) on the richness and composition of periphytic algae in lentic environments of the Upper Paraná River floodplain, over a six-year period. Other factors, such as connectivity of the environments with the main channel of the river and the availability of substrate for the periphyton, were also evaluated. For qualitative analyses, periphyton community was sampled from adult petioles of Eichhornia azurea Kunth taken from the littoral regions of the lakes studied. A total of 457 taxa of periphytic algae, distributed within 141 genera and 10 classes, were registered in the four environments. The greatest richness of periphytic algae was observed in connected floodplain lakes, especially in 2007 and during high water periods. In both connected and disconnected lakes, richness correlated positively with water levels of the Paraná River. Richness was also positively correlated with the number of taxa of aquatic macrophytes. The specific composition of periphytic algae differed between high and low water periods, and between connected and disconnected lakes. Therefore, among the considered variables, it is evident that flood pulse constitutes the principal force acting on periphytic algae communities of the floodplain, followed by the degree of connectivity and the presence of aquatic macrophytes.

Periphytic algae of the Garças Lake, Upper Paraná River floodplain: comparing the years 1994 and 2004 / Algas perifíticas da Lagoa das Garças, planície de inundação do Alto Rio Paraná: comparação entre os anos de 1994 e 2004

The changes imposed by dams on hydrological regime, water transparence and nutrient concentrations downstream affect biodiversity in relation to species richness and specific composition of the community. The aim of this work was evaluate this effect on periphyton, comparing richness and composition of periphytic algae in the Garças Lake, Upper Paraná River floodplain, between the years 1994, before construction of the Porto Primavera Reservoir, and after its operation in 2004. This floodplain lake showed an increase in species, from 113 in 1994 to 159 in 2004. A few species, however, were common during the last year, dominated by Zygnemaphyceae and some Bacillariophyceae species. The increase in algal diversity in 2004 may be the result of the ability of the system to adapt to environmental changes. However, the large change in the periphyton species composition suggests further impacts on the food web, demanding continuity of long-term studies in order to determine their consequences on the biodiversity as a whole.

As mudanças impostas pela formação de reservatórios afetam a biodiversidade das algas perifíticas em relação à composição e riqueza de espécies. O objetivo deste trabalho foi comparar a riqueza e composição de espécies de algas perifíticas na Lagoa das Garças, planície de inundação do Alto Rio Paraná, entre os anos de 1994, antes da construção do reservatório de Porto Primavera, e em 2004, após seu funcionamento. Para a lagoa registrou-se um aumento na riqueza de 113 espécies em 1994, para 159 espécies em 2004. Contudo, poucas espécies foram comuns, sendo dominadas por Zygnemaphyceae e Bacillariophyceae. O aumento na riqueza de algas em 2004 pode estar indicando a capacidade do sistema em adaptar-se às alterações ambientais, com possíveis alterações na cadeia alimentar. Considera-se fundamental a continuidade de estudos de longo prazo para avaliar as conseqüências da alteração na riqueza e composição de espécies de algas perifíticas para a estrutura e o funcionamento da planície como um todo.

Effects of hydrological regime and connectivity on the interannual variation in taxonomic similarity of periphytic algae / Efeito do regime hidrológico e da conectividade na similaridade taxonômica de algas perifíticas: variação interanual

The aim of this study was to analyze the effects of flood pulses (intensity) on the richness and composition of periphytic algae in lentic environments of the Upper Paraná River floodplain, over a six-year period. Other factors, such as connectivity of the environments with the main channel of the river and the availability of substrate for the periphyton, were also evaluated. For qualitative analyses, periphyton community was sampled from adult petioles of Eichhornia azurea Kunth taken from the littoral regions of the lakes studied. A total of 457 taxa of periphytic algae, distributed within 141 genera and 10 classes, were registered in the four environments. The greatest richness of periphytic algae was observed in connected floodplain lakes, especially in 2007 and during high water periods. In both connected and disconnected lakes, richness correlated positively with water levels of the Paraná River. Richness was also positively correlated with the number of taxa of aquatic macrophytes. The specific composition of periphytic algae differed between high and low water periods, and between connected and disconnected lakes. Therefore, among the considered variables, it is evident that flood pulse constitutes the principal force acting on periphytic algae communities of the floodplain, followed by the degree of connectivity and the presence of aquatic macrophytes.

Este trabalho visou analisar o efeito do pulso de inundação (intensidade) sobre a riqueza e composição de algas perifíticas, ao longo de seis anos, em ambientes lênticos da planície de inundação do Alto Rio Paraná. A influência da conectividade dos ambientes com a calha principal do rio e disponibilidade de substratos para a comunidade de algas perifíticas também foi avaliada. Para análise, a comunidade perifítica foi amostrada de pecíolos adultos de Eichhornia azurea Kunth, retirados da região litorânea das lagoas estudadas. Considerando os quatro ambientes, foram registrados 457 táxons de algas, distribuídos em 141 gêneros e 10 classes. A maior riqueza de algas perifíticas foi observada em lagoas conectadas, com destaque para o ano de 2007 e para o período de águas altas. A riqueza apresentou correlação positiva, nas lagoas conectadas e não conectadas, com nível hidrométrico do Rio Paraná. Também esteve correlacionada positivamente com o número de táxons de macrófitas aquáticas. A composição de algas perifíticas diferiu entre os períodos de águas altas e águas baixas e entre lagoas conectadas e não conectadas. Ficou evidente que, dentre as variáveis consideradas, o pulso de inundação constitui a principal função de força atuando sobre a comunidade de algas perifíticas na planície, seguido pelo grau de conectividade e presença de macrófitas aquáticas.