Banca de QUALIFICAÇÃO: RAYANE FERNANDES VANDERLEY
Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.DISCENTE : RAYANE FERNANDES VANDERLEY
DATA : 01/11/2018
HORA: 09:30
LOCAL: Sala de Reuniões - DECOL
TÍTULO:
Driving factors of cyanobacteria dominance in tropical semiarid reservoirs
PALAVRAS-CHAVES:
cyanobacteria dominance, eutrophication, nutrient, n/p ratio, community, composition, phytoplankton.
PÁGINAS: 50
GRANDE ÁREA: Ciências Biológicas
ÁREA: Ecologia
RESUMO:
Harmful cyanobacterial blooms are one of the most severe problems in freshwater ecosystems and since mid-20th century have become much more recurrent due to anthropic disturbances. Understanding the causes of cyanobacteria dominance is crucial to develop an effective management strategy. Nutrients levels, specially nitrogen and phosphorous are considered key factors to comprehend cyanobacteria blooms dynamics. Despite of this, in environments that are constantly enriched, such as many semiarid reservoirs in Brazil, other factors should regulate cyanobacteria dominance. Researches have been considered N:P ratio as a good predictor of the phytoplankton community structure in freshwater ecosystems because they are sensitive to changes in nutrient concentration these changes. In light of this, low N:P would shift to N-limitation in phytoplankton and favours N-fixing cyanobacteria due to their ability to access atmospheric N2 supply. The aim of the present study was to (1) access the trophic status and environmental scenario of six reservoirs located at Brazilian semiarid, (2) to test the effects of nutrient concentrations, (3) N:P ratios and (4) abiotic variables on phytoplankton community composition in those six reservoir. Our hypothesis are that (1) stoichiometric ratio would explain cyanobacteria dominance and (2) low N:P would favours cyanobacteria dominance. Water from six reservoirs was sampled during 12 months for analyses of limnological parameters, nutrients and phytoplankton composition and biomass. Five of six reservoirs were characterized as enriched, i.e. supereutrophic or hypereutrophic and one of them showed mosotrophic conditions. We did not find a relationship between N:P supply ratios and cyanobacteria dominance. Moreover there was a positive effect of phosphorous on phytoplankton fresh weight only in the mesotrophic reservoir, which may indicate that above a certain threshold nutrient, is not anymore a factor controlling phytoplankton community.
MEMBROS DA BANCA:
Interno - 1362202 - JOSE LUIZ DE ATTAYDE
Interno - 2412921 - JULIANA DEO DIAS
Externo ao Programa - 233.792.888-88 - KEMAL ALI GER - UFRN
Presidente - 1345773 - RENATA DE FÁTIMA PANOSSO