Inventário e dinâmica da sucessão de macrófitas aquáticas no sistema lacustre do Vale do Rio Doce, Minas Gerais, Brasil

Abstract

This thesis is dedicated to the composition and dynamics of succession of the aquatic flora species in the Rio Doce valley lacustrine system, the third largest Brazilian natural lakes system. One third of all lakes was recognized as Ramsar site, while the remaining two thirds are subjected to significant degradation of their surroundings. This impact can cause an increase in sediments and nutrients load that can alter the state of the lake from oligotrophic to eutrophic. The first chapter refers to aquatic flora species composition and distribution in protected and surrounding areas located in the Rio Doce valley lakes. Furthermorewe propose the creation of a new life-form category, rafted plant, applied to plants established on floating meadows. The second chapter deals through remote sensing, the succession of aquatic macrophytes. The aim is to verify wherever the floating islands are occurring, how much space they are occuping and if the history of recent human interferences can help explain the formation of large areas of floating islands within the Rio Doce lacustrine system. We recorded 184 aquatic macrophyte species, one new species to science, in different taxonomic groups (Carophyta, Pteridophyta and Angiosperm) and eight life forms. A floristic similarity characterization between protected and surrounding areas indicated that 26% of all species are unsafe because they do notoccur in this conservation unit. We conclude that the occurrence of floating islands has relation with degradation of the surroundings of the lakes, affecting about one hundred of them. Was verified also that information about the types and the total number of aquatic environments in lacustrine system were lagged until the present work, which may contribute to the conservation of natural resources in the region.