BACTERIA IN THE CASTLETON KARST, DERBYSHIRE, ENGLAND

The Castleton area contains an extensive and complex karst drainage sy stem. Recharge is provided by allogenic stream sinks and by infiltrati on into a soil covered autogenic catchment. Concentrations of the sani tary indicator bacteria faecal coliform (FC) were measured weekly over a 84-week period at three stream-sinks (P6, P7 and P8) and at two con trasting springs (Russet Well and Peak Cavern Rising). Russet Well dra ins 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 Wel l system. Over the year as a whole and during each three-month season, median FC concentrations at P6 were significantly higher than at Russ et Well. The difference was greatest during summer/autumn and was lowe st in winter/spring and it appears that FC concentrations at the risin g are a complex function of faecal inputs and flow-through time. The r elationship between FC concentrations at Russet Well and at Peak Caver n Rising proved to be complex. Over the sampling period as a whole and during the spring and autumn there was no significant difference betw een median FC concentrations at the two risings; during the winter, wh en discharge was highest, median FC concentrations at Russet Well were significantly higher than at Peak Cavern Rising; and during the summe r FC concentrations at Peak Cavern Rising were significantly higher th an at Russet Well. The high FC concentrations in the sinking streams a nd 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 o f FC bacteria indicates that even soil covered karat systems are unabl e to filter out potentially harmful micro-organisms.