Produção primária com ênfase na excreção de matéria orgânica dissolvida por populações fitoplanctônicas naturais do reservatório de Barra Bonita, SP
Resumen
To quantify the primary productivity in a fixed sampling station at the Barra Bonita Reservoir, monthly sampling from July/03 to August/04 were performed in three different depths in the euphotic zone (surface; 1.0; 3.0 and 5.0 m). These were incubated in situ during 4 h with NaH14CO3 using light and dark flasks. The results showed that in the summer and rainy periods (dec/03, feb/04 and mar/04), higher values of total assimilated organic carbon were obtained. Similarly, higher values of PAR (Photosynthetic Available Radiation) were obtained. The particulate organic carbon recently photosynthesized represented 93.5 %, whereas the dissolved fraction represented 6.8 % in relation to the total incorporated carbon. It was also observed that high primary productivity values were supported by high chlorophyll-a concentration, high concentration of excreted organic matter and the occurrence of algal blooms of the most abundant algal species in the reservoir. The present results indicate an increase in the eutrophication process in the reservoir.