Palaeoecological evidence for the timing and causes of lake acidification in Galloway, South West Scotland

During the contract period sediment cores from six lakes, three with non-afforested and three with partially afforested catchments, were analysed to enable lake water acidity (pH) to be reconstructed over approximately the past 200 years. The sites are all situated on granitic rocks in the Galloway Hills of S.W. Scotland. The results of diatom analysis show that five of the six lakes have become considerably more acid over this time period and that the acidification process is mainly independent of catchment afforestation effects. {210}^Pb dating of the sediment shows that there has been little change in sediment accumulation rates at sites with non-afforested catchments, but there has been significant increases in accumulation rate at afforested sites associated with erosion caused by pre-planting catchment ploughing. Pollen analysis indicates that no major vegetation change has occurred at the non-afforested sites whilst trace metal analysis of L. Enoch (not funded by this contract) shows elevated levels of Pb, Cu, and Zn 1n the upper, post 1800 sediments. It is concluded that acid precipitation is the most likely cause of acidification at these sites

Acid Lakes in the Galloway Uplands, South West Scotland: catchments, water quality and sediment characteristics

Reports of diminishing salmonid fisheries and increasing acidity of lakes and streams in S.W. Scotland have attributed the cause to low pH precipitation (Wright &Henriksen 1980) and afforestation effects (Harriman & Morrison 1982). In 1981 we initiated a project with CEGB funding to examine the history of lakewater acidity in both afforested and unafforested catchments in the Galloway uplands (see frontispiece). Analysis of diatom remains in lake sediments is used to reconstruct lake pH change over the past 150 years at each site. Sediment chronology is provided by lead-210 dating (Appleby & Oldfield 1978). Contemporary limnological data on water quality and diatom communities has been collected over an annual cycle (1981-82) to aid evaluation of the sedimentary data

Palaeoecological evaluation of the recent acidification of Lochnagar, Scotland

Lochnagar, a high altitude, relatively deep, come lake, lies on the Royal Deeside ESUHC of Balmoral, in an area which experiences moderate levels of acid deposition, The loch catchment comprises granite bedrock and is dominated by bare rock but overlain in places with blanket peals, Lochnagar may thus be considered potentially susceptible to acidification, The contemporary pH of the loch water is c. 5,0

Palaeoecological evaluation of the recent acidification of Loch Laidon, Rannoch Moor, Scotland

Palaeoecological techniques have been utilised to examine the recent acidification status of Loch Laidon, a large freshwater loch on Rannoch Moor, Scotland

Land-Use Experiments in the Loch Laidon Catchment

This report presents the results from the Stream Water Quality component of the Loch Laidon catchment land-use experiment which commenced in 1992. The experiment was established with the aim of examining the effects of cattle grazing on the aquatic and terrestrial habitats and biota of a moorland area of upland Scotland

Diatoms and acid lakes. Proceedings of a workshop of the 8th International Diatom Symposium, Paris, September 1984

Diatom analysis of lake sedimentshasbecome one of the most important techniques used in the contemporary debate on lake acidification. In recent years the relationship between diatom assemblages and pH has been quantified allowing the pH history of individual lakes to be reconstructed. Much reliance is placed on these reconstructions yet we have little understanding of the causal mechanisms that underlie the impressive statistics. There has been little research on the ecology and physiology of diatom taxa in acid and acidifying waters and we have little information on the role of either planktonic or non-planktonic diatoms in acid lake ecosystems. This Workshop, hence, was not only devoted to the exchange of information on current research projects but also to a discussion of some of the ecological questions that require resolution to improve our understanding of the diatom:pH relationship

A Bayesian palaeoenvironmental transfer function model for acidified lakes

A Bayesian approach to palaeoecological environmental reconstruction deriving from the unimodal responses generally exhibited by organisms to an environmental gradient is described. The approach uses Bayesian model selection to calculate a collection of probability-weighted, species-specific response curves (SRCs) for each taxon within a training set, with an explicit treatment for zero abundances. These SRCs are used to reconstruct the environmental variable from sub-fossilised assemblages. The approach enables a substantial increase in computational efficiency (several orders of magnitude) over existing Bayesian methodologies. The model is developed from the Surface Water Acidification Programme (SWAP) training set and is demonstrated to exhibit comparable predictive power to existing Weighted Averaging and Maximum Likelihood methodologies, though with improvements in bias; the additional explanatory power of the Bayesian approach lies in an explicit calculation of uncertainty for each individual reconstruction. The model is applied to reconstruct the Holocene acidification history of the Round Loch of Glenhead, including a reconstruction of recent recovery derived from sediment trap data.The Bayesian reconstructions display similar trends to conventional (Weighted Averaging Partial Least Squares) reconstructions but provide a better reconstruction of extreme pH and are more sensitive to small changes in diatom assemblages. The validity of the posteriors as an apparently meaningful representation of assemblage-specific uncertainty and the high computational efficiency of the approach open up the possibility of highly constrained multiproxy reconstructions

Lake Acidification in the United Kingdom II. A preliminary report to the Department of the Environment under Contract PECD 7/10/167

This report summarises progress made in Department of the Environment project PECD 7/10/167 - "causes and extent of lake acidification in the United Kingdom". It includes data and results available at the present time and indicates where work is still in progress. We expect that all work will be completed on schedule and that a final report will be issued shortly after completion of the contract (March 31st 1990)