Carnegie study finds algal blooms have become more intense and climate change is to blame 

Blooms of potentially toxic algae have become more intense over the past 30 years thanks to climate change

  • Study looked at  71 large lakes in 33 countries across six different continents
  • Found reasons for blooms varied, this included  fertilizer use and rainfall
  • The team determined lakes with the least warming improved the most 

Algal blooms are invading lakes all over the world, a global survey has revealed.

Researchers have found this aquatic phenomena has become more frequent and intense over the last 30 years.

Although the reasons for the increase varied from lake to lake, the team determined that lakes with the most improved algal blooms experienced the least warming over the past three decades — suggesting climate change could be the a culprit.

Researchers have found this aquatic phenomena has become more frequent and intense over the last 30 years. Pictured is Lake Khanka on the border between Russia and China

The findings come from the Carnegie Institution of Science, which used 30 years of data from NASA and the US Geological Survey’s Landsat 5 near-Earth satellite.

The satellite monitored the planet’s surface between 1984 and 2013 at to reveal long-term trends in summer algal blooms in 71 large lakes in 33 countries across six different continents.

The team then partnered with Google Earth Engine in order to process and analyze some 72 billion data points.

Anna Michalak, a researcher at Carnegie said, ‘We found that the peak intensity of summertime algal blooms increased in more than two-thirds of lakes but decreased in a statistically significant way in only six of the lakes.’

Reasons for the increase varied from lake to lake, the team determined that lakes with the most improved algal blooms experienced the least warming over the past three decades -- suggesting climate change could be the a culprit. Pictured is Lake St. Clair on the border between the United States and Canada

Reasons for the increase varied from lake to lake, the team determined that lakes with the most improved algal blooms experienced the least warming over the past three decades — suggesting climate change could be the a culprit. Pictured is Lake St. Clair on the border between the United States and Canada

The satellite monitored the planet's surface between 1984 and 2013 at to reveal long-term trends in summer algal blooms in 71 large lakes in 33 countries across six different continents Pictured  is Florida's Lake Okeechobee

The satellite monitored the planet’s surface between 1984 and 2013 at to reveal long-term trends in summer algal blooms in 71 large lakes in 33 countries across six different continents Pictured  is Florida’s Lake Okeechobee

‘This means that algal blooms really are getting more widespread and more intense, and it’s not just that we are paying more attention to them now than we were decades ago.’

Algal blooms, although aesthetic pleasing, are harmful because they are home to toxin-producing phytoplankton, which is destructive to both humans and the environment.

And there have been numerous reports just in the past 10 years, such as the ones that shut down Toledo’s water supply in 2014 or led to states of emergency being declared in Florida in 2016 and 2018.

During the study it was found that the reason for more-intense blooms varied for each lake - this included fertilizer use, rainfall, or temperature. Lago de Cahora Bassa (pictured)  in Mozambique was one of the lakes that had improvement over the 30-year period

During the study it was found that the reason for more-intense blooms varied for each lake – this included fertilizer use, rainfall, or temperature. Lago de Cahora Bassa (pictured)  in Mozambique was one of the lakes that had improvement over the 30-year period

During the study it was found that the reason for more-intense blooms varied for each lake  – this included fertilizer use, rainfall, or temperature — one clear finding was found across the board.

Among the lakes that improved at any point over the 30-year period, only those that experienced the least warming were able to sustain improvements in bloom conditions. 

HEALTH RISKS OF ALGAL BLOOMS 

 Technically called cyanobacteria, the ancient class of organisms that create the blooms are present nearly everywhere water is found, but thrive in warm, still bodies like lakes and ponds.

They also create a unique class of toxins, the impact of which on humans is only partly understood.

Long linked to animal deaths, high doses of the toxins in humans can cause liver damage and attack the nervous system.

In the largest outbreaks, hundreds have been sickened by blooms in reservoirs and lakes, and officials in some areas now routinely close bodies of water used for recreation and post warnings when blooms occur.

But less is known about exposure at lower doses, especially over the long term.

Small studies have linked exposure to liver cancer – one toxin is classified as a carcinogen, and others have pointed to potential links to neurodegenerative disease.

This suggests that climate change is likely already hampering lake recovery in some areas.

‘This finding illustrates how important it is to identify the factors that make some lakes more susceptible to climate change,’ Michalak said. 

‘We need to develop water management strategies that better reflect the ways that local hydrological conditions are affected by a changing climate.’

 

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