IS THERMAL STABILITY IS REALLY IMPORTANT FOR ENVIROMNENTAL HETEROGENEITY AND PHYTOPLANKTON DISTRIBUTION IN TROPICAL LAKES

Luciana Gomes Barbosa

Resumo


Aim: To evaluate the effects of the environmental heterogeneity promoted by the thermal stratification on the distribution of limnological variables and phytoplankton functional groups. Material and Methods: Samplings were performed out monthly in the vertical profile of two natural lakes, one shallow and monomitic and the other one deep and meromitic, over five years. We analyzed the limnological variables and phytoplankton functional groups. Results: The environmental contrasts promoted by the thermal matrix were reflected in the heterogeneity of vertical distribution of light, nutrients and functional groups. Thus, during the stratification, groups NA, A and X1 were distributed in the epilimnion, with light availability and nutrient limitation, and R in metalimnion and hypolimnion associated with high concentrations of N-NH4 and P-PO4-3. Seasonally, changes in climatic conditions (eg. reduction of the air temperature) have promoted the breakdown of water column stability during the mixing period, with reduced environmental heterogeneity. As a consequence, changes in the vertical position of the phytoplankton occurred with collapse of the populations of NA (epilimnio) and R (metalimnion and hypolimnion) and favoring of cyanobacteria (S1), dominant throughout the water column. Conclusion: The higher thermal stability and partial atelomixis were the key role in the higher heterogeneity, favouring the increase de functional groups richness and biomass stability of the R and NA groups.


Palavras-chave


Atelomixis, thermal stratification, heterogeneity.

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