The flowering of toxic algae that can be fatal to humans is increasing worldwide with rising temperatures, according to the first global survey of dozens of lakes on freshwater lakes, based on 30 years of Nasa data.
The increase is driven by climate change, escaping the chemicals used in agriculture and urban development, according to research published in the journal Nature.
In humans, algae blooms cause symptoms such as thorns, stiffness, tremors, increased speech, gastric burns and fever. They also release toxins that can cause liver damage, lead to respiratory paralysis or create other fatal conditions.
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Many dogs have been killed after drinking water containing algae blooms.
Researchers at the Carnegie Institution of Science used data from the Nasa satellite and US Geological Survey near Lansat 5 to probe the planet between 1984 and 2013. They studied long-term trends in 71 large lakes in 33 countries on six continents and analyzed more than 72 billion data points.
Statements by co-author Effe Shaw from the Carnegie Institution of Science Independent: "It is known that nutrients such as nitrogen and phosphorus are the main drivers of algae blooms. Usually they enter lakes and reservoirs after extreme events to participate and when they are in the lake, warmer temperatures worsen the algae.
"Climate change means extreme weather events are increasing the flow of these chemicals."
There were very few lakes in which algal blooms improved, the researchers found. The lake that was least warmed at least suggests that global warming is opposing management efforts to improve water quality.
"We found that the maximum flowering intensity in the summer increased by more than two-thirds of lakes, but decreased statistically significant in only six lakes," said co-author Anna Michalak of the Carnegie Science Institute.
"This means that algal blooms are really becoming more widespread and intense, and it's not just that we are paying more attention to them now than we were decades ago."
Studies suggest they cost $ 4 billion each year in the United States alone. The sharp increase in algae populations has led to bans from lakes in the Pacific Northwest to the entire Mississippi Sea and Lake Huppatkong, the largest lake in New Jersey.
In May this year a sudden seaweed kills at least eight million salmon in a week through Norwegian fisheries. The algae held onto the fish from the fish and choked them.
The Norwegian Fisheries Directorate said more than 10,000 tonnes of agricultural salmon had been killed, with a selling price of about 620 million Norwegian kroner (56 million pounds).
Similar algae blooms have been reported on the west coast of Scotland. killing thousands of fish in Loch Yin with hundreds of tons of dead fish removed after the bloom.