浙江义乌市城镇化对溪流底栖硅藻群落的影响

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

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。

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（P0.05）.The percentage of IPA also positively correlated to the percentage of eutraphentic and the percentage of pollution-tolerant diatom taxa（P0.05）.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.