Search

The purpose of this study was to characterize five crater lakes in Los Tuxtlas, Mexico, on the basis of morphological, physical, chemical, and biological features. A bathymetric map of each lake was obtained and morphometric parameters were calculated. Physical and chemical parameters (temperature, transparency, nutrients, pH, conductivity, cations) and chlorophyll a were measured for three periods: the cold season (January), the dry season (May), and the rainy season (October) of 2000. The trophic state of each lake was determined using Carlson's indices for transparency and chlorophyll a. The lakes studied have the morphometric characteristics of maar-type volcanic lakes. Majahual, Chalchoapan, and Manantiales are the deepest lakes with elliptical basins and are classified as warm monomictic systems; Verde and Mogo are shallow lakes with conic basins and are warm polymictic. Majahual and Chalchoapan had an anoxic hypolimnion, while at Manantiales a metalimnetic oxygen maximum was measured. Sodium was the dominant cation in the five lakes, while bicarbonate was the dominant anion. Nutrient and chlorophyll a concentrations, transparency, and trophic indices suggest that Chalchoapan, Verde, and Mogo are eutrophic lakes with tendencies toward hypereutrophy; Manantiales and Majahual, in contrast, can be classified as mesotrophic lakes. The trophic state of lakes was indirectly related to deforestation and to the use of agricultural fertilizer in Los Tuxtlas as well as to certain morphometric characteristics. [ABSTRACT FROM AUTHOR]