The Palaeolimnology of Lough Murree, a Brackish Lake in the Burren, Ireland

Abstract

Lough Murree, a rock/karst barrier lagoon, is superficially isolated from the sea and seasonal variations in lake water level reflect precipitation and groundwater variation. Lake salinity is influenced by subsurface saline intrusions, occasional barrier overwash together with precipitation and groundwater inflow, leading to poikilohaline conditions. Palaeolimnological reconstructions in Murree support the supposition that the lagoon was once superficially connected to the sea around the mid-nineteenth century. Physical, chemical and biological proxies suggest an evolution to more freshwater conditions. Uncertainties about the timing of the transition persist because of an unresolved sediment chronology. The isolation of Murree from the Atlantic Ocean has promoted the formation of dense charophyte beds composed of lagoonal specialist species, which are able to tolerate large variations in salinity.