The Annual Fluctuation Of Plankton And Water Quality As Well As Fish Composition Analysis Based On The EDNA Approach In Changshou Lake

Changshou Lake is the largest artificial lake in Chongqing as well as in the southwest of China, which also provide the very important city drinking water reservoir.But along with the rapid development of agriculture, industrialization, tourism and urbanization, especially the implement of cage aquaculture in 1990 s, eutrophication in the lake occurred and became more frequent and severe. In recent years, the ecological environment protection for Changshou Lake has attracted great attention to the department of environmental protection in Chongqing, and a series of restoration measure has been carried out and several achievements has been accomplished.This study investigated phytoplankton and zooplankton and water quality using regular methods, as well as fish species composition base on environmental DNA, a nondestructive approach in Changshou Lake in order to provide basic data for ecological environment protection.The samples were collected from three monitoring sites in February, April, June and October and December of 2015 for phytoplankton, zooplankton and water physical and chemical quality analysis, including water temperature, dissolved oxygen(DO), total nitrogen(TN), total phosphorus(TP), chemical oxygen demand(COD), ammonia(NH3-N), nitrite nitrogen(NO2--N), pH and aquatic organisms species compostion, biomass were measured. The results were as following:199 taxa of phytoplankton were identified, which belonged to 75 genera of 8 phyta. The number of species of Chlorophyta ranked the first(39.2%), followed by Bacillariophyta(28.6%) and Cyanophyta(15.6%). The phytoplankton density and biomass were 483.462 104ind/L and 3.889 mg/L. 103 species of zooplankton were identified, which belonged to 51 genera, among which there Rotifera 44.6%、Copepoda 28.7% and cladocera 26.7%. The zooplankton density and biomass were 150644.4 ind/L and 4.885 mg/L. Using Shannon-Weiner diversity index(H value) and the Pielou evenness index(J value), the water quality evaluation results revealed that the water was in moderate pollution and light pollution evaluating from zooplankton diversity index, and in a positive healthy stateevaluating from phytoplankton diversity index.The water quality monitoring results in Changshou Lake showed that the average temperature was 20.7 ℃; TN concentration ranged in 0.491 to 7.804 mgL-1, with a mean of 3.435 mgL-1. TP concentration ranged in 0.057 to 0.264 mgL-1, with a mean of 0.110 mgL-1. TP concentration ranged in 4.24 to 10.05 mgL-1, with a mean of 6.13 mgL-1. NH3-N annual average concentration was 0.159 mgL-1. NO2--N annual average concentration was 0.089mgL-1. The annual trend of physical and chemical indicators showed lower inspring and winter, and higher in summer and fall. Single factor evaluation results showed that total nitrogen and total phosphorus were the main pollutant in Changshou Lake. The P valueusing Nemero index method was 4.3, which indicated that the water quality in the lake maintain heavy pollution situation.Through with extracting the Changshou Lake environmental DNA samples, and after PCR amplification with fish universal primers, five fish species including silver carps(Hypophthalmichthys molitrix), bighead carp(Hypophthalmichthys nobilis), common carp(Cyprinus Carpio), grass carp(Ctenopharyngodon idellus), Pseudorasbora parva, were detected in those samples using random cloning method for sequence analysis. Seven fish species including silver carps(Hypophthalmichthys molitrix), bighead carp, common carp, grass carp(Ctenopharyngodon idellus), Pseudorasbora parva, Rhinogobio cylindricus, Ochetobibus elongates were detected using Illumina MiSeq sequencing method.