Research on Characteristics of Epiphytic Organism of Two Submerged Macrophytes and its Response to Water Depth

Epiphytic organism is important primary producer in lake ecosystem. The study on the epiphytic organism is ecologically significant in aquatic rehabitation. Two kinds of dominant submerged plants’ epiphytic organism were selected as the research objects at Gehu Lake in Tai lake area in China. Based on the way of microscopic count and 16S rRNA high throughput sequencing, the influence of different water depth (0.6 m, 1.2 m, 1.8 m and 2.4 m) was investigated on Myriophyllum spicatum and Potamogeton malainus epiphytic algae and bacteria’s composition and diversity. The results showed that the distribution of microbial communities on surface of submerged plant were related to the water depth and species, the autotrophic index of M.spicatum were larger than P.malaianus under any water depth gradient in the test groups. Furthermore, the AI value of the small depth of 0.6~1.2 m was higher, the AI value of the medium and large water depth of 1.8~2.4 m was lower in the test groups. There were significant difference in epiphytic algae composition between two submerged macrophytes with water depth (P<0.05), the community of epiphytic algae living on two submerged macrophytes were dominated by Chlorophyta and Bacillariophyta. Significant difference was also found in epiphytic bacteria composition between two plants with water depth (P < 0.05), in which most of bacterial were Proteobacteria, Firmicutes, Bacteroidetes and so on. There was a high similarity of the epiphytic bacteria’s composition and abundance between the same plant and the water layer, more unique bacterial species were found in the small water depth of 0.6~1.2 m. It indicated that the diversity of epiphytic algae in Myriophyllum spicatum was larger than that in Potamogeton malainus, however, the diversity of epiphytic bacteria in two plants was quite the contrary. The diversity of two plants’ epiphytic algae and epiphytic bacteria was often the highest in the medium water depth of 1.2~1.8 m. Strengthening the research on the characteristics of water depth on the epiphytic organism living on submerged macrophytes, it was reference to explore the mechanism of lake ecological recovery.