Phytoplankton Community Structures And Their Reponse To Ecosystem Restoration In Huizhou West Lake, A Tropical Lake In Southern China

The paper reports the phytoplankton community of Huizhou West Lake (Guangdong province), and evaluates the trophic state and effects of Ecosystem Restoration of the lakes by analyzing species composition, quantity (cells density and biomass) and dominant species of phytoplankton. The results showed that, North South Lake, South Feng Lake, North Feng Lake, East Pinghu, West Pinghu, Ling Lake and Crocodile Lake all were eutrophic, and the cells density of the lakes arranged between 123.55×106-248.60×106 cells/L, and the dominant group was Cyanophyta.We investigated the phytoplankton of restored area and Pinghu (un-restored area) from June 2008 to May 2009 monthly in order to reveal the response of phytoplankton to lake ecosystem restoration. The results showed that, in comparison with Pinghu, both the community structure and the quantity of phytoplankton of the restored area changed greatly. The annual average biomass and cell density were 0.31mg/L and 2.75×106 cells/L, respectively, and much lower than Pinghu 3.27mg/L and 197.46×106 cells/L. While in Pinghu, Cyanophyta almost dominated all around the year, and some species, such as Pseudoanabaena become the most abundant species. However, some species from Cryptophyta, Chrysophytax and Pyrrophyta dominated in restored area instead of Cyanophyta. In addition, Margalef species richness index of phytoplankton in restored area was 3.70, significantly higher than that in Pinghu (2.68). Thus, the ecosystem restoration by re-establishing macrophyte dominance is an efficient way to control the development of phytoplankton and improve the aquatic environment of lakes.