The Hengill area is located in southwest Iceland, at the triple junction of the Reykjanes Peninsula Volcanic Zone, the Western Volcanic Zone and the South Iceland Seismic Zone (see map). It comprises an active volcano, numerous hot springs and fumaroles, and a stream system spanning three valleys, which is exposed to geothermal activity. Cold groundwater is differentially heated by steam from boiling geothermal water reservoirs, creating a temperature gradient of 4-25 ºC across the Hengladalsá river and 16 of its major stream tributaries. This form of heat exchange means the streams are not contaminated with chemicals (such as sulphur), normally associated with other geothermal areas. Given that the streams are all connected to the same main river stem, differences in the community structure and ecosystem functioning can largely be attributed to temperature effects. Scientific researchers have been studying the Hengill area since 2002 as a natural laboratory for global warming impacts.

Scientific Research

There is a wide-range of international research groups working on different aspects of the Hengill system, including representatives from Iceland, America, Britain, Ireland, Denmark and France. Háskóli Íslands and the Veiðimálastofnun in Iceland have funded research at Hengill since 2002, including the initial characterisation of the streams. PEER-funded research investigated the impact of nutrient enrichment in addition to warming impacts in the system. NERC-funded research examined impacts of warming on community persistence through time and food web structure, while ongoing research aims to use individual metabolism and body size to predict warming impacts on aquatic food webs. Ongoing NSF-funded research looks at the effects of temperature on ecosystem process rates, ecological stoichiometry and energy flow, as well as whole-stream warming experiments. BES-funded research examines the effect of geothermal warming on the terrestrial food webs bordering the streams and quantifies the impact of terrestrial subsidies to the aquatic system. Further details of all these research projects can be found on this website [here].
Above: Aerial view of Hengill
(photo by Adrianna Hawczak)

Above: Map of the Hengill streams

Above: the Hengill valley
(photo by Eoin O'Gorman)