Biogeochemical processes and the diversity of Nhecolândia lakes, Brazil

Autor(es)

Almeida, Teodoro I. R. ^[1] ; Calijuri, Maria do Carmo ^[2] ; Falco, Patricia B. ^[2] ; Casali, Simone P. ^[2] ; Kupriyanova, Elena ^[3] ; Paranhos Filho, Antonio C. ^[4] ; Sigolo, Joel B. ^[1] ; Bertolo, Reginaldo A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Escola Engn Sao Carlos, BR-13566590 Sao Carlos, SP - Brazil

^[3] Russian Acad Sci, Inst Plant Physiol, Moscow 127276 - Russia

^[4] Univ Fed Mato Grosso do Sul, Ctr Ciencias Exatas & Tecnol, BR-79000060 Campo Grande, MS - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Anais da Academia Brasileira de Ciências; v. 83, n. 2, p. 391-407, JUN 2011.
• Citações Web of Science: 11

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. (AU)

• Processo FAPESP: 06/61052-4 - Estudo da genese das lagoas da baixa nhecolandia, ms, baseado em dados de ph, composicao quimica e limnologica e altitude relativa de lagoas alcalinas e acidas.
• Beneficiário: Teodoro Isnard Ribeiro de Almeida
• Modalidade de apoio: Auxílio à Pesquisa - Regular