Avaliação da variabilidade espectral do coeficiente de absorção específico dos pigmentos fitoplanctônicos no reservatório de Barra Bonita, Rio Tietê, SP

In this work, we investigated the spectral variability of the specific phytoplankton absorption coefficient, a*φ, collected in two field campaigns carried out in a eutrophic reservoir. Such study is important in order to understand the phytoplankton growth dynamic considering the spatial and seasonal aspects, photosynthesis process in different phytoplankton group and primary production. The goal was to find spectral features associated with the chlorophyll-a and other accessory pigments present in different phytoplankton species. Measurements of absorption coefficient of phytoplankton, aφ, and chlorophyll- a concentration were determined in laboratory to obtain a*φ spectrum. The outcome showed that there is a variability of phytoplankton species due to the different spectral features obtained in the sampling stations distributed along the reservoir. Basically, all the a*φ spectra exhibited a peak at approximately 630 nm, related to phycocyanin pigment present in cyanobacteria. Couple of spectra showed a peak around 460 nm associated with chlorophyll-b and c. Carotenoids features at about 490 nm and 540 nm were also found in curves acquired in May. Such spectral features are found in phytoplankton groups already identified in the study area such as Chlorophyceae, Bacillariophyceae, Cyanophyceae, Conjugatophyceae, Chrysophyceae, among others. The findings of this work may assist in future researches about phytoplankton identification from remotely sensed data