Spatial and temporal evaluation of the diversity of freshwater Ascomycetes from the touristic channel Santa Cruz, Xochimilco, Mexico

Abstract

The diversity of freshwater Ascomycetes was determined in the touristic channel Santa Cruz, Xochimilco, Mexico. Two surveys were conducted in 2007 during the dry and wet season. Four sampling sites were selected in the channel margin, based on the level of urbanization. At each sampling site, wood panels of Tabebuia donnell-smithii, Bucida buceras, Pinus sp., Cupressus lindlei and Abies religiosa were submerged during 8 weeks. Water temperature, dissolved oxygen, organic matter, phosphorus and most probable number of coliform bacteria were determined. Results were evaluated using the diversity index of Shannon and the index of similarity of Sørensen. The highest Ascomycete diversity recorded (H’ = 1.152) was found at the third sampling site, located near commercial florist greenhouses. The lowest diversity (H’ = 0.976) was obtained at the first sampling site, in front of Santa Cruz pier. Both values of diversity were in agreement with the urbanization level and physicochemical and bacteriological data. The wet season had the lowest diversity of freshwater Ascomycetes, perhaps due to the effect of the rainfall in this aquatic environment.