Brazil has, in its territory, an extremely rich and very important set of continental aquatic ecosystems, represented by rivers, lakes, artificial dams, flooded areas with great morphometric and morphological diversity and a “natural capital” of great ecological value,
economic and social. Natural floodplain lakes of tributaries and the Amazon River in large flood valleys, large internal deltas in the Paraná, Paraguay and Uruguay rivers, and temporary lakes in Lençóis Maranhenses are ecosystems that represent evolutionary processes between climatic, chemical, geological, physical and biological conditions in complex interactions.
These ecosystems distributed mainly in the two large hydrographic basins – Amazon and Prata basin – present a biological diversity that is the expression of these evolutionary processes and whose complexity has been studied, mainly in the area of Limnology, which underwent a rapid and important transformation in the accumulation of knowledge of these ecosystems in Brazil in the last 30 years (Tundisi & Matsumura- Tundisi 2008, Esteves et al 2011).
The preservation of this “natural capital” and its biodiversity are fundamental in Brazil due not only to its importance in the hydrosocial cycle, but also its situation and location in tropical and subtropical regions where physical, chemical, biological and physiological processes still interact not fully known scientifically and needing investment in research and development. The interaction between the dynamic climatology of the Amazon region, the geomorphological basis, the biodiversity and fluvial dynamics, and the great spatial and temporal variations play a relevant role in establishing the relationships between terrestrial and aquatic biodiversity and the biogeophysical basis of the Amazon region.
The main hypotheses that explain the formation of barriers that separate populations and cause differentiation and speciation in the Amazon Basin are: population refuge hypothesis; hypothesis of isolation from barriers formed by rivers; isolation of pockets of biodiversity;
isolation of rainforests from the highest relief areas on the periphery of the Amazon Basin; hypothesis of spatial heterogeneity (the greater the spatial heterogeneity, the greater the biodiversity); intermediate disturbance hypothesis – frequent landscape changes with meanders, reorganization of riparian forests along rivers (Salati & Marques 1984, Sioli 1984, Barthem et al 1991, Barthem 1999, Barthem & Goulding 2007, Haffer 2008, Salo et al 1986).
The various possibilities of speciation apply to the entire Amazon Basin, and include flood valleys in tributaries, meandering rivers and large inland deltas. Equally important as aquatic ecosystems and depositories of biodiversity resulting from evolutionary processes are the
floodplains and wetlands of southern Brazil, coastal lagoons located in connection with or close to estuaries and estuaries with mangrove vegetation (Lacerda et al 2006 and 2008) and the temporary waters of the semiarid region of northeastern Brazil. In this context, the permanent lakes of the Doce river valley in Minas Gerais (Tundisi & Saijo 1997) and the artificial reservoirs distributed throughout the national territory that are used for a large number of functions and that constitute a important reserve of continental waters in Brazil (Agostinho et al 2007).
The biodiversity of aquatic ecosystems in Brazil is high and its origin and speciation are precisely in the different evolutionary processes and large temporal and spatial scales that occur and are taking place (Caliman et al 2010). Scientific knowledge of this biodiversity and its dynamics.
Spatial and temporal in impacted systems and preserved systems has developed intensively and dynamically, but it is necessary to invest more in the knowledge of the processes and dynamics of this biodiversity in the face of climate change and impacts from the basins
hydrographic Valuing aquatic ecosystem services for human well-being is an urgent and necessary task in Brazil. Biodiversity conservation is essential to address the basic integrity characteristics of aquatic ecosystems (Bicudo & Bicudo 2010). Biodiversity plays a key role in maintaining ecosystem resilience through functional groups of organisms.
This biodiversity of aquatic ecosystems has been threatened by the following factors: eutrophication from the use of fertilizers in agriculture; discharge of untreated domestic sewage; contamination by toxic metals and organic substances such as pesticides and herbicides; morphological degradation of rivers, lakes and coastal lagoons; removal of riparian vegetation; removal of flooded areas; construction of reservoirs; increased inland fisheries, and invasion of alien species introduced intentionally or accidentally (Rocha et al 2005).
The removal of transitional systems such as riparian forests and floodplains compromises the dissipation of erosive forces, loss of ecological functions such as the protection of biodiversity, loss of flood control capacity and opportunities for recreation and cultural activities ( Silva et al 2011). The main focus should be on increasing the efficiency of agricultural production and not increasing the planted area.
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