Distribution of diatom assemblages in the surface sediments in Sri Lankan reservoirs located in the main climatic regions and potential of using them as environmental predictors

Abstract

Diatom assemblages preserved in surface sediment are widely used for the bio-assessment of reservoirs and the present study is carried out to evaluate the distribution of diatom assemblages in reservoirs and potential of using diatom communities as indicators along with physical and chemical measurements from the reservoirs. Non-urban, shallow, small-scale reservoirs which span among three major climatic zones (Wet, Dry and Intermediate zones) were selected for the study. The present study reveals that most of the study reservoirs belong to the eutrophic category. From all the study reservoirs a total of 76 diatom taxa belonging to 46 genera were identified. Of these, the highest diversity was recorded from the Dry Zone. Aulacoseira granulata was the most dominant taxa whereas Achnanthidium, Pinnularia, Cymbella, Frustulia, Synedra, Eunotia, Nitzschia, Navicula, Cyclotella, Stauroneis and Gomphonema were also recorded at high abundane and widely distributed. The study reveals A. granulata, Achnanthidium, Nitzschia, Cyclotella and Diatoma inhabit in organically polluted eutrophic waters while Synedra acus, Synedra ulna and Amphora ovalis are the prime indicators of cultural eutrophication. Canonical correspondence analysis identified phosphate, dissolved oxygen, nitrite, conductivity and total dissolved solids as the most important measured environmental variables that could account for the distribution of diatom assemblages. However, the results of the present study reveal that the species distribution may depend on integration of a series of environmental variables and unmeasured environmental variables are also important in structuring diatom assemblages.