Using data from 464 lakes in North and South America, scientists have determined that temperature by itself does not influence the biomass of blue-green algae blooms, and that phosphorus concentration is the more defining factor.
The study says that a lot of attention has been paid to possible links between rising temperatures due to human activities and cyanobacteria blooms. While algae blooms do occur in summer, it is instead because that is the time of year when nutrient inputs from natural runoff, lake sediments and human activities are at their highest, the study found. In addition to phosphorus, nitrogen abundance also has an effect, but it’s most apparent in lakes less than three metres deep.
In the Université Laval study, geography department Professor Dermot Antoniades says the studied bodies of water are distributed along a 14,000 km north-south gradient, from Tierra del Fuego in Argentina to Ellesmere Island in Nunavut.
“No matter how hot it is, if there is no phosphorus and nitrogen, there will be no cyanobacteria blooms. Conversely, they can flourish in very cold climates,” Antoniades explained in a statement from the university, where he is also a researcher at Université Laval’s Centre for Northern Studies.
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The algae water temperature study used a remote sensing technique called Medium-Resolution Imaging Spectrometer, or MERIS, that can detect reflected light from cyanobacteria pigments in the water. Researchers found “no clear association” between the latitude of the studied lakes, their position along a climatic gradient and the biomass of the cyanobacteria living in them. The selected lakes are located in areas with climates ranging from equatorial to polar.
The study highlights the case of a lake in Resolute, Nunavut, one of the coldest inhabited places in the world, which had experienced algae blooms in the past.
“Wastewater from the airport and military base was bringing nutrients into this lake,” says Antoniades.
The study included researchers from eight countries, including Sylvia Bonilla, visiting professor at Université Laval’s Department of Biology and professor at the Universidad de la República in Uruguay.
