珠江河网典型水草床与贝类群落生物量特征

于2015年和2018年12月初调查珠江河网4个江段(左滩、小塘、外海和榄核)的典型水草床群落生物量时空变化特征,同时调查了相应江段的水草床、邻近非水草床区域的主要贝类生物量时空变化,并利用CCA分析其与主要水文、水质及沉积环境因子的相关性。结果表明:珠江河网典型水草床群落主要以刺苦草为优势种,偶伴生金鱼藻、穗状狐尾藻和轮叶黑藻等种类;对比两次调查结果发现,除小塘江段水草床生物量(以鲜重计)维持较稳定,高达9 kg·m^-2以外,其余3个江段的水草床均有种类减少、生物量下降的消落趋势。小塘江段贝类生物量最高,均值达968.8 g·m^-2,显著高于其他江段;所调查江段水草床区域中的贝类均高于非水草床区域;在由浅至深的水草床区域,虽然水草生物量逐增,但其贝类生物量却逐减;相同江段非水草床区域的贝类生物量显著低于水草床区域,表明珠江河网水草床为贝类提供良好的栖息、生长和繁育生境。径流量和水位变化可能是驱动珠江河网典型水草床群落年际演替的主要因素,而水草优势种类的保持可能受沉积物粒径组分和水体流速等因子的调控。

Biomass of typical submerged macrophyte beds and shellfish communities in the Pearl River network in China

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 of968.8 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.