Abstract
Control of nutrients, mainly nitrogen (N) and phosphorus (P), plays a significant role in preventing cyanobacterial blooms (harmful algal blooms (HABs)). This study aims at evaluating changes in the risk of the occurrence of cyanobacterial blooms and advancing the understanding of how nitrogen and phosphorus affect the growth of cyanobacteria in a eutrophic lake, Lake Vombsjön, in southern Sweden. Our results show that TP (total phosphorus) has stronger positive correlation with cyanobacteria biomass than DIP (dissolved inorganic phosphorus); DIN (dissolved inorganic nitrogen) has a stronger negative correlation with cyanobacteria biomass than TN (total nitrogen); and DIN:TP has a stronger negative correlation with cyanobacteria biomass than TN:TP. The highest amount of cyanobacteria biomass, above WHO (World Health Organization) Alert Level 2 (10 mm3/L) for drinking water correspond to the DIP/TP ratio below 10. To diminish the growth of cyanobacteria in Lake Vombsjön, TP and DIN control should be in focus, preferably a TP below 20 µg/L, and the DIN:TP ratio should be maintained at a level of at least above 10, but preferably above 50, thereby reducing the likelihood for a nitrogen limiting situation which may favor cyanobacteria dominating blooms.
Highlights
Harmful algal blooms (HABs), those caused by cyanobacteria, have become one of the most critical concerns for drinking water supply, as well as for maintaining the ecological and economic sustainability of freshwater ecosystems worldwide [1,2]
Eutrophication is the major process stimulating the growth of algal and cyanobacterial biomass, the key factors here being the maintaining of a high availability of important nutrients, such as phosphorus (P) and nitrogen (N), and a low N/P ratio [3,4]
Recent studies have demonstrated that synergies between climate warming and increasing levels of humic substances in runoff are able to trigger an increase in cyanobacteria biomass [6], as well as a reduction in the biodiversity of phytoplankton [7,8]
Summary
Harmful algal blooms (HABs), those caused by cyanobacteria, have become one of the most critical concerns for drinking water supply, as well as for maintaining the ecological and economic sustainability of freshwater ecosystems worldwide [1,2]. Recent studies have demonstrated that synergies between climate warming and increasing levels of humic substances in runoff are able to trigger an increase in cyanobacteria biomass [6], as well as a reduction in the biodiversity of phytoplankton [7,8]. Both global and local scale adaptive management tools are important to manage future challenges related to water security and adequate functioning of freshwater ecosystems [7]. They cause unpleasant smells, Water 2018, 10, 919; doi:10.3390/w10070919 www.mdpi.com/journal/water
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