Evidence for the pollution of Loch Ness from the analysis of its recent sediments

For sites, such as Loch Ness, Scotland, which are often assumed to be pristine, it is difficult to assess from standard water-quality monitoring techniques whether long-term change due to pollution is taking place. In this study, the historical record held in the sediments was used to identify whether the Loch suffers from acidification or eutrophication. A sediment core was taken in 170 m of water and analyzed using palaeolimnological techniques. Evidence from spheroidal carbonaceous particles and artificial radionuclides indicates that the Loch has been contaminated by atmospherically deposited pollutants. Although diatom analysis shows that acidification has not occurred, there is evidence for a slight eutrophication during the past 20 years. A flood event which occurred in 1868 is recorded in the sediments. This did not have an impact on diatom communities within the lake. This paper illustrates the usefulness of palaeolimnological methods in providing an early warning of environmental change in lakes.