Egeria densa is a submerged aquatic macrophyte which, in Brazil, causes problems specially for electric energy generation. The purpose of this study was to evaluate the photosynthetic rate of E. densa in two rivers (Aguapeú and Mambu) with different limnological features, both located in the Itanhaém River Basin. This species is abundant in both rivers without causing damages to their multiple uses. Photosynthetic rates were analysed in February, May, August and November 1998 and limnological variables of the water and sediment were also measured. The highest value of gross photosynthesis (GP) was detected in May (10.06 in Aguapeú and 6.10 mgO2/gDW/h in Mambu), when under-water photosynthetic active radiation (PAR) was also high (1,126.7 and 895.8 m mol/m/s, respectively). GP, total phosphorous, total CO2 and PAR were always higher in Aguapeú River.
Aquatic macrophyte; Egeria densa; photosynthetic rate; Brazil
