The radiation input to tropical lakes is very high and the
water body heats up during the daytime and cools at night. Heat transfer between the water surface and the atmosphere produces convective nocturnal mixing. Tropical lakes, situ- ated in the lowland, are polymictic at a high temperature level, and water exchange occurs every night due to diver- gence and convergence processes. This intensive water ex- change, the high radiation and the temperature level are pa- rameters, not adequately accounted for in the nutrient load- ing concept of VOLLENWEIDER (VOLLENWEIDER 1968; OECD1982; tundisi 1990)