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Nitrogen biological fixation and uptake by phytoplankton in subtropical reservoirs with different trophic status

Grant number: 12/21254-8
Support Opportunities:Scholarships in Brazil - Post-Doctoral
Effective date (Start): March 01, 2013
Effective date (End): January 31, 2014
Field of knowledge:Engineering - Sanitary Engineering - Water Resources
Principal Investigator:Maria do Carmo Calijuri
Grantee:Davi Gasparini Fernandes Cunha
Host Institution: Escola de Engenharia de São Carlos (EESC). Universidade de São Paulo (USP). São Carlos , SP, Brazil


Reservoirs artificial eutrophication affects ecosystem services and may lead to proliferation of Cyanobacteria, some of which play a negative role on water uses. Among other factors, nutrient availability regulates phytoplankton development. Through biological nitrogen fixation, some Cyanobacteria are able to convert atmospheric nitrogen (N2) to ammonium, which is incorporated to amino acids that are essential for cell metabolism. However, nitrogen fixation is an energetically expensive process, which makes the direct assimilation of dissolved nitrogen forms preferable by phytoplankton. In this research, we will investigate nitrogen biological fixation and uptake within three reservoirs with different trophic status in the São Paulo State (Brazil). To our knowledge, this is one of the first studies analyzing such nitrogen cycle steps in subtropical freshwaters. The reservoirs will be sampled in four different seasons of the year. Besides biotic and abiotic water variables, including qualitative (species and functional groups) and quantitative (density and biovolume) aspects of the phytoplankton community, nitrogen fixation will be measured in situ through an indirect method (acetylene reduction) and a direct one (15N2 isotope). Also, nitrate, ammonium and urea uptake will be estimated through incubations in the laboratory with 15N tracer. Hypotheses concerning the temporal factor and reservoirs trophic state will be tested. Statistical procedures will help data interpretation. The schedule for 24 months, including a period as short term scholar in Montréal (Canada), allows full compliance with the goals. Based on the factors governing nitrogen fixation and uptake, recommendations will be proposed for helping sustainable management of subtropical reservoirs.

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DO AMARAL MARQUES, LUIS OTIVIO; TAFFARELLO, DENISE; CALIJURI, MARIA DO CARMO; MENDIONDO, EDUARDO MARIO; FERREIRA, MURILO DE SOUZA; FERNANDES CUNHA, DAVI GASPARINI. Phosphorus and thermotolerant coliforms' loads in Brazilian watersheds with limited data: considerations on the integrated analysis of water quality and quantity. RBRH-REVISTA BRASILEIRA DE RECURSOS HIDRICOS, v. 24, . (12/22013-4, 12/21254-8, 13/19465-3)
LUIS OTÁVIO DO AMARAL MARQUES; DENISE TAFFARELLO; MARIA DO CARMO CALIJURI; EDUARDO MARIO MENDIONDO; MURILO DE SOUZA FERREIRA; DAVI GASPARINI FERNANDES CUNHA. Cargas de fósforo e coliformes termotolerantes em bacias brasileiras com dados escassos: considerações sobre análises integradas de qualidade e quantidade de água. RBRH, v. 24, . (13/19465-3, 12/21254-8, 12/22013-4)

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