Abstract:

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.

Key words: Zhijin Cave, bryophyte community, heavy metals, monitoring