Karst terrain promotes thermal resiliency in headwater streams

The response of stream ecosystems to climate change will depend in part on groundwater processes that reduce the sensitivity of streams to atmospheric conditions.  We investigated the thermal sensitivity of streams across a gradient of groundwater inputs defined by karst terrain (carbonate parent materials) in the headwaters of the Potomac River basin in eastern North America.  We collected stream temperature data and quantified thermal sensitivity for 30 sites from the relationship between daily mean water and air temperatures.  Our analysis demonstrates that thermal sensitivity is lower for streams in karst terrain than elsewhere, and that the effect of karst terrain is more important than effects of elevation or basin size in this regard.  Our study indicates the importance of karstic groundwater for stream thermal resiliency and suggests the importance of riparian vegetation for maintaining stream temperatures elsewhere. Our study also provides a simple and rapid method for climate change research that can be implemented in conjunction with watershed organizations and citizen science networks.