Temporal heterogeneity of plankton community in Lake Dianchi and its relation to environmental factors

The plankton community in Fubao Bay of Lake Dianchi, a large, shallow and highly polluted freshwater lake in China, was investigated on three dates. First, a total of 76 zooplankton species were identified by morphological characteristics of which 44 were protozoa, 20 rotifer, and 12 crustacean. Then, the plankton community was characterized by using random amplified polymorphic DNA (RAPD) and Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) over the time period. Morphological composition, RAPD fingerprints, PCR-DGGE fingerprints, and unweighted pair-group method using arithmetic averages clustering analysis all showed that samples within a season were generally clustered into the same group. The results also revealed that RAPD fingerprints and PCR-DGGE fingerprints were identical to morphological composition in characterizing community similarity. Canonical correspondence analysis based on morphological composition, RAPD fingerprints, and PCR-DGGE fingerprints all suggested that the factors strongly correlated with the first two ordination axes were seasonally different, further suggesting high- temporal heterogeneity in Lake Dianchi. There were close relationships between morphological composition, RAPD and PCR-DGGE fingerprints, and: (1) total nitrogen in summer, (2) total phosphorus in autumn, and (3) BOD5 or NO2-N in winter. Results of this study suggest that molecular techniques are acceptable methods for examining plankton community composition and measuring plankton community responses to stress and perturbation.