浙江义乌市城镇化对溪流底栖硅藻群落的影响

于2010年4月调查了浙江省义乌地区5个参照和9个城镇溪流样点的理化性状、底栖硅藻群落及所在流域土地利用。Spearman秩相关分析表明,流域城镇化强度指标——不透水地表面积比与电导率、总氮和磷酸盐等理化因子呈显著正相关,也与喜富营养型硅藻与耐污型硅藻比例呈显著正相关。非度量多维尺度分析(NMDS)与相似性检验(ANOSIM)分析表明,参照溪流与城镇溪流的底栖硅藻群落具有显著差异。参照溪流底栖硅藻平均密度(5.67×105cell.cm-2)低于城镇溪流(6.11×106cell.cm-2),并且参照溪流运动型、富营养型和耐污型硅藻比例也显著低于城镇溪流。城镇溪流优势种是Na-vicula minima(50.75%),参照溪流为Rhoicosphenia abbreviate(55.71%)。典范对应分析(CCA)表明,森林面积比、底质组成、二氧化硅、电导率、钙离子和镁离子是影响研究样点底栖硅藻群落的主要环境因子。研究结果证实,城镇化会显著改变城市溪流底栖硅藻群落结构,底栖硅藻可作为评价溪流生态质量的指示生物。

Impact of watershed urbanization on stream benthic diatom community: a case study in Yiwu City, Zhejiang Province

Physio-chemical conditions,watershed land use,and benthic diatom assemblages were characterized in 5 reference and 9 urbanized stream sites in Yiwu City,Zhejiang Province.Spearman rank correlation analysis showed that the percentage of impervious area(IPA)in watersheds significantly and positively correlated to conductivity,total nitrogen,and phosphate(P<0.05).The percentage of IPA also positively correlated to the percentage of eutraphentic and the percentage of pollution-tolerant diatom taxa(P<0.05).Non-metric multidimensional scaling and analysis of similarities showed that the benthic diatom assemblages were significantly different between the reference and the disturbed sites.The diatom density in the reference sites(5.67×105 cell·cm-2)was less than one in the disturbed sites(6.11×106 cell·cm-2).In contrast,the percentage of motile diatom taxa,the percentage of eutraphentic diatom taxa and the percentage of pollution-tolerant diatom taxa in the reference sites were significantly lower than those in the disturbed sites.The dominant species in the reference sites was Rhoicosphenia abbreviate(55.71%)while Navicula minima(50.75%)dominated the disturbed sites.Canonical correspondence analysis(CCA)indicated that the diatom assemblage distributional patterns among the sampled sites could be significantly explained by the percentage of forests in watersheds,substrate composition,SiO2,conductivity,Ca2+ and Mg2+.In conclusion,our study indicated that benthic diatom assemblages can be used to assess the impacts of urbanization on stream ecosystems.