Abstract: The spatial-temporal variations of biomass of typical submerged macrophyte beds (SMBs) in four sampling sections (Zuotan, Xiaotang, Waihai, and Lanhe) of the Pearl River network were investigated in early December of 2015 and 2018. Meanwhile, the biomass variations of dominant shellfish species in sampling sections with SMBs and in adjacent areas without SMBs were investigated. The effects of hydrological, water quality, and sedimentary factors on the biomass of submerged macrophytes and dominant shellfish were analyzed by canonical correspondence analysis (CCA). The results showed that dominant species of typical SMBs in the Pearl River network was Vallisneria spinosa, which occasionally occurred with Ceratophyllum demersum, Myriophyllum spicatum, and Hydrilla verticillata. Both the species and biomass of SMBs in Zuotan, Waihai and Lanhe sections decreased during the two investigations except for Xiaotang section, where the biomass of SMB maintained a relatively stable level of up to 9 kg·m^-2 (wet weight). The biomass of shellfish in Xiaotang section was the highest, with an average value of 968.8 g·m^-2. The biomass of shellfish in the areas with SMBs was higher than that without SMBs. In the areas with SMBs, biomass of submerged macrophytes increased gradually with increasing water depth, whereas biomass of shellfish decreased. In the same sampling sections, biomass of shellfish in the areas without SMBs was significantly lower than that in the areas with SMBs, indicating that SMBs provided suitable habitats for the growth and reproduction of shellfish. The CCA results showed that changes in runoff and water level might be the main driving factors for the interannual succession of SMBs communities in the Pearl River network and that the maintenance of dominant species in SMBs may be regulated by the size fraction of sediment particle and water flow velocity.

Key words: fluoride exposure, bone Gla protein., alkaline phosphatase, dental fluorosis, skeletal fluorosis