Desmids Community Variation And Environmental Factors In Luoma Lake And Dongping Lake Of The East Route Of South-to-North Water Diversion Project

Desmids are groups with rich number of Chlorophyta. Desmids are important indicators of water quality, which play important roles in water quality and aquatic ecosystem monitoring because they are highly sensitive to environmental changes, especially water chemical changes. Luoma Lake and Dongping Lake have been employed as they are important storing lakes of the east route of the South-to-North Water Diversion Project. Thus, investigation and study of desmids in Luoma Lake and Dongping Lake can enrich relevant researches, and provide references about desmids community succession and basic data for application of desmids in aquatic ecosystem monitoring.Desmids in Luoma Lake and Dongping Lake were monitored continuously for three years (from March 2011 to May 2013). The species composition, abundance, and correlation between desmids community and environmental factors of the two lakes were investigated and analyzed primarily. The comparison of desmids community distribution characteristics between both lakes was also studied.A total of 16 species belonging to 3 genera, were identified in Luoma Lake and Dongping Lake. Fifteen species belonging to 3 genera were identified in Luoma Lake, including 3 Closterium species,9 Cosmarium species, and 3 species Staurastrum. Seven species belonging to 3 genera were identified in Dongping Lake, including 1 species of Closterium,5 species of Cosmarium, and 1 species of Staurastrum. Species of Cosmarium were abundant in the two lakes.Abundance of desmids in Luoma Lake and Dongping Lake showed similar seasonal variation. Monitoring frequency of desmids density in summer and autumn were higher than that in winter and spring. Species of Cosmarium were dominant in both lakes. Desmids abundance in Luoma Lake was 0～45.8×104 cells·L-1 with the maximum which occurred in August 2012 at S5 station. While the abundance of Dongping Lake was 0～17.4×104 cells·L-1 with the maximum which occurred in November 2012 at N3 station.Canonical correspondence analysis (CCA) and Pearson correlation analysis were used to analyze the correlation between desmids community distribution and environmental factors. The results showed that the major environmental factors influencing desmids distribution in Luoma Lake were transparency (Trans) and ammonia nitrogen (NH4+-N), and those in Dongping Lake were total nitrogen (TN) and pH.Comparison of desmids community characteristics between Luoma Lake and Dongping Lake showed that there were differences on distribution, environmental driving factors and others of the two lakes. Desmids detection frequency in Dongping Lake was lower than that in Luoma Lake. Temperature, ammonia nitrogen and total nitrogen had obvious correlation with desmids community in both lakes. However, the value of pH had obvious correlation with desmids community in Dongping Lake, and transparency had obvious correlation with desmids community in Luoma Lake.Desmids identified in Luoma Lake and Dongping Lake were mainly indicative desmids from oligotrophic water with a low detection frequency, which indicated eutrophication in both lakes. Thus, water in Luoma Lake and Dongping Lake was not appropriate for most species of desmids to grow.