Sustaining recreational quality of European lakes: minimizing the health risks from algal blooms through phosphorus control

Abstract

Summary 1.A safe, clean water supply is critical for sustaining many important ecosystem services provided by freshwaters. The development of cyanobacterial blooms in lakes and reservoirs has a major impact on the provision of these services, particularly limiting their use for recreation and water supply for drinking and spray irrigation. Nutrient enrichment is thought to be the most important pressure responsible for the widespread increase in cyanobacterial blooms in recent decades. Quantifying how nutrients limit cyanobacterial abundance in lakes is, therefore, a key need for setting robust targets for the management of freshwaters. 2. Using a data set from over 800 European lakes, we highlight the use of quantile regression modelling for understanding the maximum potential capacity of cyanobacteria in relation to total phosphorus (TP) and the use of a range of quantile responses, alongside World Health Organisation (WHO) health alert thresholds for recreational waters, for setting robust phosphorus targets for lake management in relation to water use. 3. The analysis shows that cyanobacteria exhibit a nonlinear response to phosphorus with the sharpest increase in cyanobacterial abundance occurring in the TP range from about 20 lg L À1 up to about 100 lg L À1 .4. The likelihood of exceeding the World Health Organisation (WHO) 'low health alert' threshold increases from about 5% exceedance at 16 lg L À1 to 40% exceedance at 54 lg L À1 . About 50% of the studied lakes remain below this WHO health alert threshold, irrespective of high summer TP concentrations, highlighting the importance of other factors affecting cyanobacteria population growth and loss processes, such as high flushing rate. 5. Synthesis and applications. Developing a more quantitative understanding of the effect of nutrients on cyanobacterial abundance in freshwater lakes provides important knowledge for restoring and sustaining a safe, clean water supply for multiple uses. Our models can be used to set nutrient targets to sustain recreational services and provide different levels of precaution that can be chosen dependent on the importance of the service provision.Key-words: algal bloom, blue-green algae, ecosystem services, freshwater, lake, nutrient, quantile regression, WHO *Correspondence author. E-mail: laca@ceh.ac.uk † On secondment from CEH 2 to JRC 1 .

Combating cyanobacterial proliferation by avoiding or treating inflows with high P load—experiences from eight case studies

“…In other deep lakes, a substantial decrease in biomass to values \1 mm 3 L -1 was also shown for P. rubescens once TP concentration dropped below 20 lg L -1 (Haslauer et al 1984;Dokulil and Teubner 2012). Similar thresholds have been found in two studies evaluating data from several hundred European water bodies showing that below 20 lg L -1 TP cyanobacteria hardly ever reach high biomass, but their likelihood to become abundant increases with increasing TP concentration, starting in the range of 20 and 100 lg L -1 and particularly above 50 lg L -1 (Chorus and Niesel 2011a;Carvalho et al 2013). Also for Canadian lakes Downing et al (2001) showed an increasing risk of cyanobacterial abundance with TP concentration between 10 and 100 lg L -1 , and a risk of at least 50 % with higher concentrations.…”

“…Although some research have reopened the debate about the necessity to reduce nitrogen (N) in addition or instead of phosphorus for lake remediation (e.g. Conley et al 2009;Paerl et al 2011), this position has been scientifically challenged (Carpenter 2008;Schindler 2012), and it has been widely demonstrated that eutrophication can be most efficiently reversed by the reduction of phosphorus (Vollenweider 1976;Jeppesen et al 2005;Carvalho et al 2013). …”

Lake Area Changes and Their Influence on Factors in Arid and Semi-Arid Regions along the Silk Road

“…However, in arid and semi-arid areas, many lake areas have decreased sharply because of drought, global warming, strong evaporation, and increasing population, with a great increase in water consumption for life and production [1]. Playing a key role in hydrological cycles, lakes affect many aspects of society and ecosystems, such as water storage, moderation of climate, and energy production and irrigation, especially in arid and semi-arid regions [7][8][9][10][11]. Meanwhile, fluctuations in lake areas may result in disasters such as floods in humid regions and water shortages in arid and semi-arid regions [12,13].…”

Effects of laser irradiation on a bloom forming cyanobacterium Microcystis aeruginosa

“…The wide spread of algal blooms limits the use of lakes and reservoirs for drinking water sources and recreational activities (Weirich and Miller 2014). Toxins produced by cyanobacteria can pose serious risks to aquatic organisms, even human beings, and may cause fatal consequences (Carvalho et al 2013;Steffen et al 2014). Therefore, the prevention and control of algal blooms are of great importance for the health of humans and animals.…”