high quantity organic matter that enters the aquatic system
through litter fall (Rivera-Monroy et al., 1995). This organic matter
becomes a source of nutrients and other substances through decomposition
processes that affect the composition and productivity
of phytoplankton communities (Herrera-Silveira and Ramı´rez-
Ramı´rez, 1996; Rivera-Monroy et al., 1998).