During the Year of Coasts and Waters 2020, we’ve been featuring NatureScot staff working along our shorelines and waterways to gain an insight into the varied work they do. In our final blog of the series, we join Freshwater and Wetlands Advice Manager Iain Sime on the slopes of Dark Lochnagar to learn more about our important work on water monitoring.

NatureScot helps support the important long-term monitoring project, the UK Upland Waters Monitoring Network.  For more than 30 years it has provided a unique and extremely valuable long-term record of the water chemistry and biology of upland lochs and streams across the UK. The network was originally established to monitor the chemical and ecological impact of acid deposition (‘acid rain’) in areas of the UK that are sensitive to acidification.  It has evolved since to also examine a far wider range of pressures facing upland waters including nitrogen deposition, climate change and land use change.

I recently used my NatureScot volunteering day to help collect chemical and biological samples from a site within the network, Lochnagar, in the eastern Cairngorms.  This sampling usually takes place during the summer, but with Covid restrictions the fieldwork was delayed this year. I joined Ewan and James Shilland, who have both worked on the network for many years.  At the moment Ewan is doing his PhD at Queen Mary University of London, University College London and the Natural History Musuem London, funded by NERC and NatureScot.  He is studying how the aquatic plant communities have responded to changes in water chemistry over time, and is evaluating whether environmental DNA (eDNA) offers a further tool to help understand these changes over long timescales. 

Lochnagar sits in a corrie, high on the mountain of the same name, at an altitude of 788m. Work conducted by scientists at University College London and the Freshwater Fisheries Laboratory at what is now Marine Scotland in Pitlochry, demonstrated that the loch had become heavily acidified by acid rain over a period of 150 years or more. On the day we visited, we were collecting water chemistry and plankton samples, filtering water for eDNA analysis and downloading data from loggers that are permanently located around the loch.  Various sensors and samplers are also positioned within the loch in order to monitor water temperature across a range of depths, and capture recent sediment. 

The findings from over three decades of monitoring at Lochnagar and the other sites within the network show some startling results. Perhaps most strikingly, they show that the sulphate concentration in the water has fallen dramatically. This has been linked directly to large regional scale reductions in the emissions of sulphur from power stations and other industrial sources over the last four decades, and the consequent reduction in sulphur deposition across the UK land surface. 

This is despite Lochnagar being a long way from most air pollution sources.  The reduction in sulphate has been accompanied by a welcome increase in pH and large drop in the concentration of labile aluminium, which is highly toxic to fish and aquatic invertebrates, as the water becomes less acidified.  These trends are even more marked in more southerly lochs, such as in the Merrick Kells SSSI in Galloway, the Lake District and North Wales.

Despite the high winds giving rise to an estimated wind chill of -11^oC, loch level data was successfully downloaded from the outflow of Lochnagar and the opposite side of the loch, just below the imposing cliffs that lead to the summit.  To collect samples for eDNA analysis, a lot of water was filtered through some bespoke filter apparatus.  Although genetic research such as this is relatively new, and seeing rapid advances in understanding and technologies, some more basic technologies are also required.  So, in the cold conditions, when fingers don’t work so well and the filter can clog up with the peaty water, using a DIY plunger from Screwfix really helps speed up the process!

Long-term datasets such as the UK Upland Waters Monitoring Network can also reveal important surprises.  In common with all the other sites on the network, concentrations of Dissolved Organic Carbon (that causes a brown staining of some upland waters) has been increasing progressively over the last 30 years.  The data from the network helped establish this is due to a natural response of catchment soils; as they recover from acidification.  This is not such good news for water companies that use upland catchments for public water supply, as it can increase their treatment costs – although this has also helped increase their interest in restoring peatlands to keep the water, and the carbon, in the soils. 

Such patterns of change often only become apparent over long timescales, and with the help of research and measurements of consistently high quality.  But helping collect the samples also provided a welcome day out in the mountains, where we also got to see some of the other local land-based residents including peregrine, a sea eagle, ptarmigan and mountain hares.  Not bad for an extremely windy but very welcome day in the hills.