VARIAÇÃO TEMPORAL DE UMA COMUNIDADE FITOPLANCTÔNICA DO RESERVATÓRIO DE APM-MANSO ATRAVÉS DE MODELAGEM ECOLÓGICA TRIDIMENSIONAL

Abstract

TEMPORAL  VARIATION  OF  A  PHYTOPLANKTON  COMMUNITY  IN  THE APM-MANSO RESERVOIR THROUGH TRIDIMENSIONAL ECOLOGICAL MODELING. The ecology of reservoirs, that are complex dynamic and man-made ecosystems, has assumed prominence in Brazil. This study explored the application viability of a tridimensional ecological modeling on phytoplankton dynamics in APM-Manso reservoir, simulating the temporal variation of phytoplankton community in two different scenarios of nutrient loading. The CAEDYM model was coupled to ELCOM, and the simulation was conducted in two stages: one hydrodynamic and other ecological. The period of five months, from Septemper 1th, 2005 was chosen for the simulation. Two simulation scenarios were constructed, the first containing the actual values of nutrient loading of the main tributary rivers measured in field, and the second with a reduction in nutrient load of these rivers, simulating a possible replacement process to grazing areas from forested areas in Manso's River basin. The simulation showed rapid responses of phytoplankton to nutritional availability, and the results obtained corroborated several theories about alga's adaptive strategies and dynamics. Among the simulated Classes, Bacillariophyceae and Cryptophyceae were more sensitive to load reduction, while Chlorophyceae and Cyanophyceae, despite having their biomass lowered, suffered less from the impact, suggesting that they are more adapted to nutrient limitation. The rain peaks positively influenced the growth rates of Bacillariophyceae in Scenario 1. A trend of replacing the dominance of Cyanophyceae to Chlorophyceae was observed in both simulations.

keywords: Ecological modeling; ELCOM; CAEDYM; phytoplankton; limnology