Species diversities and habitat characteristics of submerged plant communities in Beijiang River valley, Guangdong

Objective To provide references for protection of submerged plant resources in Beijiang River valley and surrounding areas, Guangdong.

Method The species diversity of submerged plant communities and the water quality where these plants grow were investigated from 2009 to 2013 using on-site survey and quadrat survey methods.

Result A total of 11 angiosperms and one macro-alga were recorded at five sites, Zhengjiang of Renhua County (SG1), Beijiang of Qujiang District (SG2), Wujiang of Zhengjiang District (SG3), and Nanshui of Ruyuan County (SG4 and SG5). All recorded plants belong to widespread species. The dominant species were Potamogeton wrightii, Hydrilla verticillata, Vallisneria denseserrulata, and Myriophyllum spicatum. It was the first time that P.maackianus was recorded in Guangdong. The water quality test results showed that the major pollutions in Beijiang River valley were TN, TP, NH₄⁺-N and COD_Cr. Except for TN and NH₄⁺-N, the contents of the other parameters at two sites(SG4, SG5) of Nanshui met or approached the class Ⅰ level of National Water Quality Standard, and the contents of TN and COD_Cr at the other sites were between class Ⅱ and Ⅲ. The contents of TP, NH₄⁺-N and COD_Cr were relatively high in winter, while TN contents were relatively high in summer.

Conclusion The species richness of submerged plants in Beijiang River valley is relatively low. The species diversity of the plant community is closely related to local human activities, with the species richness and diversity being the highest in Nanshui where the water quality is the best, and the lowest in Zhengjiang where the water quality is the worst. Industrial pollution, building of hydropower station dam and sand-excavating are the major factors causing declining of the species diversity of the submerged plants in Beijiang River valley.