Projeto de pesquisa

Planktonic metabolism (GPP, CR and NCP) will be estimated through the euphotic zone (3-4 sampled depths). To evaluate the planktonic metabolism, different methods will be used concurrently. The 13C method (Slawyk et al. 1977), the 18O method (Grande 1982; Bender et al. 1987) and the dark/light method (Carpenter 1965; Carrit and Carpenter 1966) will be used as incubation methods and the bio-optical method (Gorbunov and Falkowski 2005) and the O2:Ar method will be used as free-incubation methods. For the use of 18O and O2:Ar methods and its analyses, we will collaborate with Dr. Nicolas Cassar from Duke University (N. Carolina, USA). He is an expert on the use of 18O and O2:Ar methods to measure marine planktonic metabolism and has already the required materials for sampling and analyses. This collaboration will allow to compare concurrently different methods and to determine with more accuracy the metabolic balance of the planktonic community in this coastal region. For the incubation methods, the bottles will be incubated on deck at in situ temperature and adjusting the incident natural light to that received in situ using neutral density screens. The 13C, 18O and dark/light methods are subject to the potential bottle effect. Nevertheless, for those methods, quartz bottles will be used during the incubation, letting pass through the UV radiation.
Furthermore, bacterial abundance will be evaluated by flow cytometry upon staining with SYBRGreen I (Gasol and del Giorgio 2000). Downwelling irradiance and incident irradiance will be measured in the PAR, UV-A and UV-B using narrow bands radiometer. Dissolved organic matter (DOM) fluorescence will be evaluated at different excitation/emission couples with a spectrofluorometer (Obernosterer et al. 1999) to quantify and characterize CDOM. Nutrient (silicate, phosphate and nitrate+nitrite) and chlorophyll concentrations will be measured. We propose also to measure the variation of O2.