A report published today (Wednesday, April 27) has revealed that 97% of monitored Scottish lochs and reservoirs increased in temperature between 2015 and 2019.
While most (88%) warmed by 0.25°C to 1.0°C/year over this period, 9% increased by more than that – some by up to 1.3°C/year.
Researchers behind the Assessing climate change impacts on the water quality of Scottish standing waters report, from Scotland’s Centre of Expertise for Waters (CREW), warn that these changes increase the risk of harmful algal blooms developing.
These blooms could restrict the water's use for recreation and water supply, and as a safe habitat for wildlife.
Minister for Environment, Biodiversity and Land Reform Mairi McAllan said that this research is "worrying".
"It is vital that we do more to mitigate those impacts, to seek to reduce the pace of warming but also to adapt to it," she said.
"Research like this will be hugely valuable in informing the development of policy solutions and measures to mitigate and adapt to climate change, and also protect, restore and enhance these vital natural assets.”
The report makes a number of recommendations, which include reducing the amount of phosphorus and nitrogen entering lochs and reservoirs from their catchments, because these are the main driver of algal blooms.
Sources of these plant nutrients - present in synthetic fertilisers as well as human and animal waste - include farm runoff and waste water discharges, according to the Scottish government which funds CREW.
It also recommends revision and implementation of policy changes. In particular, it said there is an "urgent need" to updated the publication ‘Cyanobacteria (Blue-Green Algae) in Inland and Inshore waters: Assessment and Minimisation of Risks to Public Health – Scottish Government Revised Guidance (2012)’.
"We trust the recommendations proposed will enable effective climate action for safeguarding freshwaters now and during the critical decades ahead," said Dr. Pauline Lang, project manager for CREW.