Cyanobacteria – also known as blue-green algae – have proliferated much more rapidly than other algae in lakes across North America and Europe over the past 200 years, and in many cases the rate of increase has sharply accelerated since the 1900s, finds a study led by Zofia Taranu of McGill University.
Cyanobacteria. Image credit: Josef Reischig / CC BY-SA 3.0.
“We found that cyanobacterial populations have expanded really strongly in many lakes since the advent of industrial fertilizers and rapid urban growth,” said Zofia Taranu, who is the first author of the paper published in the journal Ecology Letters.
“While we already knew that cyanobacteria prefer warm and nutrient-rich conditions, our study is also the first to show that the effect of nutrients, such as phosphorus and nitrogen, overwhelm those of global warming.”
According to the scientists, cyanobacteria can produce toxins that cause damage to the liver or nervous system. The most common symptoms of acute exposure to harmful algal blooms are skin rash or irritation, gastroenteritis and respiratory distress. Chronic, low dose exposures over a lifetime may also result in liver tumors or endocrine disruption.
Preliminary studies also suggest that a recently isolated cyanotoxin may become more concentrated across food chains and may be associated with the formation of progressive neurodegenerative diseases such as Alzheimer’s, Parkinson’s and ALS diseases.
The rapid increase in cyanobacteria identified by Zofia Taranu and her colleagues in the new study points to the potential for a parallel increase in the concentration of harmful cyanotoxins.
The scientists took sample cores of sediment from 108 lowland and alpine lakes located in North America and Europe and analyzed them for pigments left behind by blue-green algae.
The analysis showed that during the past two centuries, more than half of the lakes (58 per cent) had seen significant increases in concentrations of blue-green algae pigments, whereas only 3 per cent showed a significant decrease in the presence of the microorganism.
Lowland lakes in agricultural catchments were found to be especially susceptible to cyanobacteria increases.
The study also found that since 1945 the incidence of blue-green algae has increased more rapidly than the growth of other types of water-borne algae.
More significant increases were observed in the more temperate lowlands (61 per cent in North America and 70 per cent in Europe) which were closer to areas of agricultural activity than in alpine areas (36 per cent).
_____
Zofia E. Taranu et al. Acceleration of cyanobacterial dominance in north temperate-subarctic lakes during the Anthropocene. Ecology Letters, published online February 26, 2015; doi: 10.1111/ele.12420
