Abstract
Over recent decades, Iceland has experienced a decline in conventional agriculture, a rapid increase in tourism and significant climatic change, all of which can potentially influence lake ecosystems. To investigate limnological changes over the past 70 years, sediment cores were collected from two lakes: Hafravatn, near Reykjavík and surrounded by summerhouses, and Grænavatn, a less accessible lake 25 km south-west of Reykjavík. Analyses of chironomid head capsules and geochemical parameters reveal that Hafravatn is well-buffered against increasing human activities and changing climate, possibly due to its larger surface area (c. 1.01 km 2 ) and depth (c. 28 m). Short-lived shifts in chironomid assemblages coincide with changes in sediment accumulation rate, associated with infrastructure projects. However, no significant correlation was found between the chironomid assemblage and the number of summerhouses present. The chironomid assemblage of Grænavatn shows long-term shifts mainly caused by changes in summer temperatures, which likely influence lake-water levels and habitat availability. Due to Grænavatn’s smaller and shallower basin (c. 0.62 km 2 , c. 4.4 m) or lack of other influences, the chironomid assemblage likely responded more sensitively to climate change. This study shows that lake size and bathymetry are important determinants of resilience to land-use and climate change in Iceland.