Relationship of spatial distribuition of Egeria densa with enviroment variables in Guarapiranga dam - SP

As macrófitas aquáticas possuem grande importância no ambiente aquático, contribuindo em diversos processos ecológicos. No entanto, o seu crescimento exagerado pode causar problemas aos sistemas aquáticos. A grande capacidade de proliferação de macrófitas aquáticas foi registrada em diversos locais da Região Metropolitana de São Paulo. A represa Guarapiranga é um dos principais mananciais dessa região e a grande colonização por Egeria densa Planchon (Hydrocharitaceae) pode afetar os usos múltiplos desse sistema. Dessa maneira, a presente dissertação apresenta no primeiro capítulo a relação de parâmetros físicos e químicos da água com a presença e a abundância de E. densa, sendo identificados dois compartimentos diferenciados pela qualidade da água e uma possível relação com a E. densa. No segundo capítulo, o efeito da declividade do litoral e da transparência da água nas populações de E. densa foi verificada por meio de regressões múltiplas. A declividade do litoral foi determinante na zonação e abundância de E. densa e a transparência da água não foi significativa para prever a abundância dessas plantas.Macrophytes have great importance in the aquatic environment, contributing in various ecological processes. However, their excessive growth can cause problems in aquatic systems. The great proliferation capacity of macrophytes was recorded in various locations in the Metropolitan Region of São Paulo. Guarapiranga dam is one of the main sources of water for this region and the colonization of Egeria densa Planchon (Hydrocharitaceae) can affect the multiple uses of this system. Thus, the first chapter of this dissertation relates the physical and chemical parameters of water in the presence and abundance of E. densa, identifying two different compartments for water quality and a possible relationship with E. densa. In the second chapter, the effect of the littoral slope and water transparency in populations of E. densa was verified by multiple regressions analysis. The littoral slope was a determining factor in zonation and abundance of E. densa and water clarity was not significant to predict the abundance of these plants

Spatial and temporal distribution of stream macroalgae in a tropical river basin

Spatial and temporal distribution of stream macroalgae in streams from southeastern Brazil were assessed for one year. The fluctuations in macroalgal species composition and environmental factors were monitored monthly. The region exhibit a tropical climate, with defined rainy and dry seasons. Nineteen species were found, with a predominance of Chlorophyta (52.7% of the species), followed by Cyanobacteria (26.3%), Ochrophyta and Rhodophyta (10.5% each). Scytonema arcangeli had the highest number of records (63.6%), while Mougeotia capucina occurred in all sampling sites. Community structure had low similarity (20-26%) and the environmental factors showed a weak contribution to the distribution pattern observed. Despite this, the light availability at the stream-bed seems to be a major influence on the macroalgal seasonal dynamics. We suggest that macroalgae communities are predominantly composed of rare species, and this could explain the lack of a clear spatial and temporal variation pattern of these organisms