岩溶洞穴苔藓群落特征及其对重金属污染的指示意义:以贵州织金洞为例

Community characteristics of bryophyte in Karst caves and its effect on heavy metal pollution: A case study of Zhijin Cave, Guizhou Province

岩溶洞穴的开发与利用导致的重金属污染严重威胁洞穴环境及地下水,因此对洞穴环境的监测具有重要的现实意义。本文通过对典型的暗河型溶洞贵州织金洞内的苔藓群落特征及其重金属污染状况进行研究,拟揭示苔藓群落对洞穴重金属污染的指示意义。共发现苔藓群落类型34个,苔藓植物种类20科33属49种,含苔类8科8属12种,藓类12科25属37种。优势科为丛藓科、凤尾藓科和提灯藓科,物种占比率分别为16%、14%、14%。Hg污染超标倍数最高达59.45倍,在距洞口不同深度均远高于Cr和Zn,说明洞内Hg污染较为严重。苔藓群落指标随着重金属污染含量的上升总体呈下降趋势。所测定的重金属中基质Hg含量与苔藓群落指标的拟合程度最好,与其对应的苔藓群落指标均呈显著负相关关系(P <0.05),说明苔藓群落特征能够很好地反映洞内Hg污染的变化趋势。RDA排序结果分析表明:洞穴苔藓群落为适应低光度环境会表现出向光性运动、喜钙生基质、耐重金属等生理特征。蛇苔(Conocephalumconicum)植物体内的Hg含量与其基质Hg含量具有显著相关性(P<0.05),说明蛇苔受基质Hg污染影响较大。在今后的治理过程中,可以考虑将蛇苔作为洞内环境的生物监测材料之一。

Heavy metal pollution caused by the development and utilization of Karst caves seriously threatens the cave environment and groundwater. Understanding the pollution dynamics has important practical significance for monitoring the cave environment. Here,the characteristics and heavy metals of the bryophytes in a typical Dark River Cave,Zhijin Cave,in Guizhou province were studied to explore the effect of the bryophyte community on cave pollution. A total of 34 types of bryophyte communities were observed,representing 49 taxa of bryophytes(12 of liverworts,37 of mosses) in 33 genera(8 of liverworts,25 of mosses) and 20 families(8 of liverworts,12 of mosses). The dominant families were Pottiaceae,Fissidentaceae and Mniaceae,comprising 16%,14%,and 14% of all taxa,respectively. Mercury(Hg) levels were up to 59.45,much higher than Cr and Zn,which indicates that Hg is the most serious pollutant in caves. The bryophyte community index showed a decreasing trend with an increase in heavy metal pollution. The Hg content of the measured heavy metals was significantly negatively correlated with its corresponding bryophyte community indices(P < 0.05),which indicates that the bryophyte community characteristics can accurately reflect the level of Hg pollution within a cave. The RDA sequencing results showed that bryophyte communities in Karst caves adapt to low photometric environment and thus exhibit photopic movement,grow well in Ca substrate and are resistant to heavy metals. The Hg content in the Conocephalum conicum was significantly correlated with its substrate Hg content(P < 0.05). This shows that C. conicum is affected by the substrate Hg pollution. In the future,C. conicum can be used as one of the biomonitoring materials for cave environments.