Large lakes worldwide share many of the same threats
Aug 21, 2019 02:13PM
● By Editor
Researchers from Cooperative Institute for Great Lakes Research lifting a water monitoring buoy out of Lake Erie. Image: Ray García
By Ray García of Great Lakes Echo - August 21, 2019
Algae pollution, plastic pollution and waste run-off plague the Great Lakes here in the United States.
But similar problems also threaten large bodies of freshwater worldwide. The seven African Great Lakes and Lake Baikal in Russia, two of the world’s largest systems of freshwater, also face these problems daily.
During the summer, a rapid growth of algae is among the most prominent challenges in Lake Erie and Lake Michigan. These algal blooms harm the lake animals and can harm humans as well. The algae produce toxins and create dead-zones. It rises to the surface and sucks the oxygen out of the water. Some lake creatures eat algae, but this type, called cyanobacteria, can overwhelm sections of water.
Areas of Lake Erie take on a bright green glow as algal blooms overwhelm the water. Image: Ray García
“These blooms really represent an ecosystem that’s out of balance. So, when you get this much growth of algae, it means it’s just not being utilized. Right, it’s not part of a normal food web cycle,” said Tom Johengen, a research scientist from the Cooperative Institute for Great Lakes Research based at the University of Michigan in Ann Arbor, Michigan.
Johengen monitors algae with a series of large buoys throughout the lakes.
On some beaches, the problem can be seen immediately; the algae swirl all around, turning the water into a thick green slime. Further out, where the buoy is located, the algae is a bit thinner but still clings to the machine as the team hefts it out of the water.
“Here we’re accumulating an algae that isn’t being eaten and obviously there’s an aesthetic issue—there’s smell and site issues,” Johengen said. “But more importantly with this particular cyanobacteria there’s an issue with its production of toxin and the need to remove that from our water treatment plants.”
This alga primarily comes from farm water run-off, through irrigation and rain. It contains things like animal waste and pesticides. These problems aren’t unique to the North American Great Lakes.
Lake Baikal in Russia is the largest body of freshwater by volume in the world. Lake Superior is larger by area, but Baikal is so deep it holds over 22 percent of the world’s freshwater. Alone, it contains more water than all the American Great Lakes combined. However, the region only has one water treatment plant, which isn’t enough to combat all the pollution that threatens it.
Last year, just like in the North American Great Lakes, large accumulations of algae that can lead to illness also harmed Lake Baikal, according to France 24 news in Paris. The Siberian lake has seen an unprecedented level of algae, indicating increased levels of pollution.
Tilapia purchased at a local fish market near Lake Victoria. These fish were photographed prior to dissection. Image: Farhan Khan – Roskilde University
In July, the Associated Press reported that toxic waste from a nearby power plant turned parts of Lake Baikal bright turquoise. Despite their potential danger, the turquoise beaches have become a popular destination.
On the other side of the world, a crisis looms at Lake Victoria. Part of the African Great Lakes, Lake Victoria is the largest lake on that continent.
In 2015, a group of Tanzanian students from the Roskilde University in Denmark found that micro plastic pollution is one of the Lake Victoria’s biggest problems. Just like in the North American Great lakes, plastic ingestion has harmed many of the lake’s 200 species of fish.
Farhan Khan, the Roskilde professor who oversaw the project, said the students conducted experiments at local fish markets.
“What they did was they went to the banks of Lake Victoria in Tanzania, and they bought fish from the market. So these are fish that anyone would buy, but in particular, they asked for the fish not to be gutted,” Khan said.
Plastic sample found in Nile Tilapia and Perch. Image: Farhan Khan – Roskilde University
For his students to determine if the fish were eating plastic, they needed the digestive tracts to remain intact. They looked at several fish, particularly Nile perch and Nile tilapia, two popular fish in the region.
“They took these fish back to the lab and they dissected the gastrointestinal track and they placed it in a strong basic solution – so sodium hydroxide. And that degraded all the tissue but it doesn’t affect plastic…. They found plastic in a number of the fish,” Khan said.
Khan’s research found that the fish they discovered with plastic show just a fraction of how much microplastic is in the water. But it is proof that microplastic is in two major resources, the water and fish.
In recent years, Kenya, Tanzania and Uganda, the three countries surrounding Lake Victoria, banned plastic bags to keep them out of the water and the food web, both on the land and in the lakes. Lake Baikal and the African and American Great Lakes make up over 65 percent of the world’s freshwater. Many of these regions are looking to address the problems but it will take time to see if the harm can be reversed.
This story was produced as part of a partnership between WKAR and Michigan State University’s Knight Center for Environmental Journalism.
To read the original article and hear an audio report on this story, follow this link to the Great Lakes Echo website. http://greatlakesecho.org/2019/08/19/large-lakes-worldwide-share-many-of-the-same-threats/