| Wuli Lake is an extension of Meiliang Bei, Taihu Lake in Wuxi City and is a typical shallow urban lake. In May, 2012, we conducted a four-week preliminary investigation of periphytic algae colonization in Wuli Lake using glass slides as an artificial substrate. The aim of the study was to better understand ecological characteristics of the periphytic algae community and add to the research base on aquatic organisms in Wuli Lake. On day 1 of the experiment, 100 glass slides were placed horizontally into the water at a depth of 10-20 cm. Beginning on day 2, three glass slides were randomly collected each day and all algae on the slide was used for species identification and biomass determination. Physiochemical parameters were measured daily in the study area and included chlorophyll-a, pH, water temperature, Secchi disk depth (SD), permanganate index (CODMn), total nitrogen (TN) and total phosphorus (TP). Results were used to analyze the relationship of water parameters with the periphytic algae community. A total of 51 periphytic algae species from 35 genera and 5 phyla were identified, dominated by diatoms (26 species, 12 genera and 51.0% of the total periphytic algae species). The most dominant species was Navicula pupula, with a dominance of 0.439. The range of periphytic algae community density was 4.96 - 23870.63 ind/mm2 with an average value of (10 682.47 ± 8 365.09) ind/mm2. The community biomass range was 9.30×10-6 - 7.10×10-2 mg/mm2 with the average value of (3.16±2.50×10-2)mg/mm2. The first peak in community density and in biomass occurred on day 11. The ranges of the Shannon-Wiener index (H), Pielou evenness index (J) and Margalef index (D) were 1.54 -2.57, 0.49 -1.00 and 1.24 - 2.52, with average values of (2.14±0.29), (0.69±0.11) and (1.91±0.3), respectively. Water quality in the study area was mesotrophic and moderately polluted, as indicated by the diversity index of periphytic algae community and the water quality parameters. Based on variations in density and biomass of the periphytic algae, the colonization process of periphytic algae in Wuli Lake can be divided into four stages: the lag phase, exponential growth phase, mature-decline phase and the secondary growth phase. Pearson correlation analysis shows that TP, TN, SD and NH4 + -N were the major environmental factors affecting development of periphytic algae community. |
