Data/hora: 29/05/2024 03:41:14

Provedor de dados: | Anais da Academia Brasileira de Ciências
País: | Brazil
Título: | Biogeochemical processes and the diversity of Nhecolândia lakes, Brazil
Autores: | Almeida,Teodoro I. R; Calijuri,Maria do Carmo; Falco,Patrícia B; Casali,Simone P; Kupriyanova,Elena; Paranhos Filho,Antonio C; Sigolo,Joel B; Bertolo,Reginaldo A.
Data: | 2011-06-01
Ano: | 2011
Palavras-chave: | Pantanal; Alkaline lakes; Saline lakes; Cyanobacteria; Alkalinization processes.
Resumo: | The Pantanal of Nhecolândia, the world's largest and most diversified field of tropical lakes, comprises approximately 10,000 lakes, which cover an area of 24,000 km² and vary greatly in salinity, pH, alkalinity, colour, physiography and biological activity. The hyposaline lakes have variable pHs, low alkalinity, macrophytes and low phytoplankton densities. The saline lakes have pHs above 9 or 10, high alkalinity, a high density of phytoplankton and sand beaches. The cause of the diversity of these lakes has been an open question, which we have addressed in our research. Here we propose a hybrid process, both geochemical and biological, as the main cause, including (1) a climate with an important water deficit and poverty in Ca2+ in both superficial and phreatic waters; and (2) an elevation of pH during cyanobacteria blooms. These two aspects destabilise the general tendency of Earth's surface waters towards a neutral pH. This imbalance results in an increase in the pH and dissolution of previously precipitated amorphous silica and quartzose sand. During extreme droughts, amorphous silica precipitates in the inter-granular spaces of the lake bottom sediment, increasing the isolation of the lake from the phreatic level. This paper discusses this biogeochemical problem in the light of physicochemical, chemical, altimetric and phytoplankton data.
Tipo: | Info:eu-repo/semantics/article
Idioma: | Inglês
Identificador: | http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652011000200004
Editor: | Academia Brasileira de Ciências
Relação: | 10.1590/S0001-37652011000200004
Formato: | text/html
Fonte: | Anais da Academia Brasileira de Ciências  v.83 n.2 2011
Fonte: | info:eu-repo/semantics/openAccess