Bacteria in the Castleton Karst, Derbyshire, England

Abstract

Abstract The Castleton area contains an extensive and complex karst drainage system. Recharge is provided by allogenic stream sinks and by infiltration into a soil covered autogenic catchment. Concentrations of the sanitary indicator bacteria faecal coliform (FC) were measured weekly over a 84-week period at three stream-sinks (P6, P7 and P8) and at two contrasting springs (Russet Well and Peak Cavern Rising). Russet Well drains the allogenic catchment, but also receives some autogenic recharge whereas Peak Cavern Rising receives only autogenic recharge except at high stage when it functions as an overflow spring for the Russet Well system. Over the year as a whole and during each three-month season, median FC concentrations at P6 were significantly higher than at Russet Well. The difference was greatest during summer/autumn and was lowest in winter/spring and it appears that FC concentrations at the rising are a complex function of faecal inputs and flow through time. The relationship between FC concentrations at Russet Well and at Peak Cavern Rising proved to be complex. Over the sampling period as a whole and during the spring and autumn there was no significant difference between median FC concentrations at the two risings; during the winter, when discharge was highest, median FC concentrations at Russet Well were significantly higher than at Peak Cavern Rising; and during the summer FC concentrations at Peak Cavern Rising were significantly higher than at Russet Well. The high FC concentrations in the sinking streams and at the risings suggest that there could be a health risk to cavers, especially during storm events and the summer. Furthermore, the fact that the waters from both springs contain significant concentrations of FC bacteria indicates that even soil covered karst systems are unable to filter out potentially harmful micro-organisms.