SEASONAL DYNAMICS OF MACROALGAL COMMUNITIES IN THE PRETO RIVER BASIN,SAO-PAULO, SOUTHEASTERN BRAZIL

Macroalgal seasonality was analyzed in nine stream segments of the Pre to River basin: five of these were sampled monthly for one year and fo ur bimonthly during two years. Seasonal variation of macroalgae was co rrelated with stream variables (temperature, current velocity, specifi c conductance, turbidity, surface light, pH and oxygen). Multiple line ar regression was applied to evaluate the macroalgal seasonal variabil ity determined by a combination of temperature, current velocity and t urbidity, the most influential environmental parameters on macroalgal seasonality. Most species revealed a clear seasonal trend, such that l ate fall through early spring was the period with highest macroalgal a bundance in most sites. Temperature, current velocity and turbidity ac count for 24 to 83 % of macroalgal species number variation and 24 to 79 % of macroalgal abundance in the basin. The results suggest that th e seasonal flow determined by the precipitation regime associated with turbidity and temperature were the major factors influencing the seas onal dynamics of macroalgal communities. The highest values of macroal gal species number and abundance were found under cooler temperatures, lower current velocities and lower values of turbidity.