Caracterização limnológica e de sedimentos da Lagoa dos Barros, Osório, Sul do Brasil

Abstract

Large shallow lakes are rare but relevant to ecosystems and humans. These systems have specific ecological characteristics related to its morphology, water and sediment characteristics. The comprehension of the processes of a lake is enhanced by analyzing its past conditions. The aim of this study was to characterize the present and past ecology conditions of Lagoa dos Barros, a lake in southern Brazilian coast. The study of present conditions combined bathymetric surveys, morphometric analyses, and assessments of water and biological communities. For the past, the analysis included evaluation of physical, chemical and biological (diatoms) components in a 35 cm sediment profile. Lagoa dos Barros shows peculiar characteristics related to its high mineral turbidity and limitation of the system productivity due to the low light availability in the water column, even with nutrients available. The base for this condition is the association between a flat and shallow morphology, the small size of sediment and the high incidence of wind in the region. In the recent past, the lake undergoned variations in turbidity and salinity conditions, evidencing its susceptibility to changes in the drainage basin associated with water level oscillations. The singularity of the lake demands an improved management of its uses.