Great Lakes Threat #213, Algal Blooms


I’ve spent most of my summertime near one Great Lake or another. I grew up a short car ride from Lake Michigan’s beaches, and when we escape to the North Woods of Wisconsin, we sometimes make the trip up to Lake Superior, one of the cleanest--coldest!--lakes I have ever visited. While living in Cleveland, I lived close to Lake Erie. I kayaked in those waters, riding the waves and feeling enchanted as I watched the water birds.

For all my love for the Great Lakes, however, I’ve had no illusions about the number of challenges they face. Often, the Racine beaches had signs warning swimmers of bacteria contamination, and we avoided others entirely because dead fish littered the sand.

My paranoia about bacteria has increasingly decreased. The EPA’s 2012 Lakewide Management Plan for Lake Michigan highlights fewer bacteria-related beach closures. But the lake faces other challenges. In particular, excess algal blooms have begun to be a worry for Lake Michigan, and a huge problem in my other favorite great lake, Lake Erie. These algal blooms present health risks for residents and organisms, decrease tourism and make life difficult for boaters and fishers.

Blooms occur when algae grows together densely, at concentrations around hundreds of cells per milliliter. They range in color: yellow-browns, greens and reds. The one that took over nearly one-fifth of Lake Erie in 2011 had a greenish hue. NASA’s photo demonstrates the extent of the algal blanket, which swirled out across the lake. It’s not something you’d be keen on swimming in.

The sheer density of algal blooms that year created catastrophe for the fish and plants living below them. With concentrations reaching up to millions of cells per milliliter, the blooms took up oxygen needed by other organisms. Worse, algal blooms naturally produce biotoxins. Scientists measured extraordinary amounts of a liver toxin during 2011, and fear that a toxin targeting the neurological system will be on the rise in future blooms.

I’d almost rather take the bacteria.

Algal blooms occur when too much nutrients, such as nitrogen or phosphorus, get into the water and sit there. Authors of a paper published in PNAS this April gave evidence that phosphorus enters the lake via fertilizer run-off from nearby farms. Exacerbated by weather conditions (stronger winds would have stirred up the lake and broken up the blooms a little better), the situation got out of control in 2011.

Weather may change year to year, but the agricultural practices remain the same, the authors concluded that while 2011 had been a record-setting year for size and concentration of algal blooms in Lake Erie, the worst is probably ahead.

Of course, scientists haven’t been sitting idly by while the blooms spread. In May, recommendations drafted by scientists at the International Joint Commission, an American-Canadian agency, will be put out for public comments. It will probably be awhile before any recommendations get put into practice. But I’m happy scientists are working together to get the extra phosphorous out of the lake, making conditions a little safer for the people and wildlife living near Lake Erie.



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