Climate change increases toxin risk in Scottish lochs

Climate change is posing a risk to water supply in Scotland because warmer water in standing waters like reservoirs and lochs increases the prevalence of toxic algal blooms, according to a report from the country’s Centre of Expertise for Waters (CREW).

Global warming has already caused a rapid and extensive warming of Scotland’s reservoirs and lochs with impacts expected to intensify, the researchers warned.

The report, “Assessing climate change impacts on the water quality of Scottish standing waters”, published by the Scottish government, showed that between 2015 and 2019, some 97% of monitored Scottish reservoirs and lochs have increased in temperature. While most warmed by up to 1.0°C per year over this period, 9% increased by more than that – some by up to 1.3°C a year.

Waters in the south and east of Scotland are expected to warm the most at first, but this climate-related impact will reach all parts of the country by 2040.

The report stressed that climate change will increase the risk of algal blooms developing in reservoirs, a source of toxins released by cyanobacteria in the blooms.

The researchers highlighted that the higher rainfall associated with climate change increased the delivery of pollutants (such as sediment and nutrient run-off) in standing waters, resulting in eutrophication, and the likelihood of algal blooms.

They pointed out that lack of rainfall and drought-conditions, also associated with climate change, reduces the flushing rate of reservoirs and lochs which, again, triggers algal growth.

The report warned that that algal blooms could also result in habitat degradation and loss of biodiversity.

Freshwater ecologist at the UK Centre for Ecology & Hydrology and lead author of the report, Dr Linda May, said the it “provided an early warning of the potential impacts of climate change on water supply”.

Funded by the Scottish government, CREW is a partnership between the James Hutton Institute and Scottish higher education and research institutes.