Diurnal dynamic of inorganic carbon and oxygen dissolved in a Nile tilapia (Oreochromis niloticus Linnaeus, 1758) fish pond, São Paulo, Brasil

• Autor(a) principal: Rodrigues,Claudinei José
• Data de Publicação: 2010
• Outros Autores: Mercante,Cacilda Thais Janson, Carmo,Clovis Ferreira do, Tucci,Andréa, Osti,João Alexandre Savilo, Genaro,Ariane Carolina Di
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Acta Limnologica Brasiliensia (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S2179-975X2010000400010
• topic: fish pond; diurnal variation; Nile tilapia; carbon dioxide; water quality; metabolism

Natural waters may play the role of sinks or carbon dioxide (CO2) emitters, depending on the physicochemical characteristics of the system (diffusion and reaction of this gas into water) as well as on the pH, and the primary production of micro-organisms as a result of the consumption of such compounds. Evidence suggests that the CO2 concentrations in ponds are mainly governed by the aquatic metabolism, i.e. by the balance between respiration and photosynthesis; AIM: The purpose of this study was to describe aspects of the metabolism of tilapia cultivation based on the dynamic and balance of the oxygen concentrations (DO) and forms of dissolved inorganic carbon (DIC): carbon dioxide (CO2) and bicarbonate (HCO3-). Other variables analyzed are: total phosphorus, water transparency, total alkalinity, water temperature, pH, underwater radiation and quantitative analysis of phytoplankton community; METHODS: Sampling was collected infor 5 consecutive days from 6:00 AM to 8:00 PM (December/2006) every 2 hours; RESULTS: During the test it was observed periodicity in the fluctuations of the DIC concentrations, being CO2 and HCO3- the predominant fractions. The values of DIC were strongly influenced by the fraction of CO2 and it was observed a predominance of the fraction HCO3- in the afternoon. CO2 concentrations ranged from 0.48 µM through 138.94 µM, reaching a daily average of 18.04 µM. The flow of CO2 in the interface atmosphere/water showed variations during the day. In the afternoon (from 12:00 PM until 6:00 PM) the variation pointed to the flow atmosphere/fish pond; however, the balance was 577 µmol.m-2.h-1 in the flow fish pond/atmosphere; CONCLUSIONS: The observed dynamics indicated that under the conditions of this study, the metabolism of aquatic organisms was the main driving force of this system, a fact corroborated by the intense process of euthrophication in the pond.