Environmental Influence on the Euglenoid Species Diversity and their Abundance in Museum Lake, Thiruvananthapuram, India

Twenty-three species belonging to the class Euglenophyceae were recorded from the Museum Lake, Thiruvananthapuram, India. A canonical correspondence analysis (CCA) between environmental variables and the dominant euglenophytes indicated interaction with certain physical and chemical parameters, in particular rainfall, electrical conductivity and phosphate versus their distribution in the Museum Lake. The dominant species were Euglena deses, Trachelomonas hispida and Trachelomonas volvocina. The CCA results indicate interaction between a variety of environmental parameters and species abundance. A closer examination suggests some external factor (e.g. evaporation) affecting water quality rather than the environment changing the algal biomass. With low rainfall the phosphate concentration increased from 1.5 to 6.9 mg P/l (likely as a result of anoxic conditions in the muddy bottom) and simultaneously nitrate was (partly) taken up by these dominant algae, as a result of which N : P ratios decreased from 4.5 to 0.7. The present study shows that the dominant euglenoid species co-occur in relatively hard water with high phosphorus concentration, and can be considered as useful bio-indicators in assessing the health and extent of deterioration of a lake ecosystem.