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In early August, the city of Toledo, Ohio raised an alarm: a bloom of toxic algae in Lake Erie had poisoned the drinking water supply for the city. Toledo residents spent days using bottled water, and officials scrambled to solve the problem. The algae faded naturally. But harmful algal blooms seem to be a growing threat to waterways all over the country.

Algae blooms are a natural phenomenon that, in some cases, can be beneficial. If conditions are right, algae will multiply in the water until they are visible as a cloud of color, often  green or red, sometimes brown. Certain kinds of algae bloom can feed many other organisms, from mussels and clams to baby fish. Others can be toxic, either to humans and other land-bound wildlife, or to other organisms in the water.

In Lake Erie, the blooming algae belonged to a genus of toxic blue-green algae called Microcystis that affects humans and wildlife. Where I live on Long Island, brown tides fill some of our lakes and bays periodically throughout the summer, smothering shellfish and the eelgrass that supports them. Red tides occur up and down the coast, poisoning shellfish so they're dangerous to eat, and depleting oxygen in the water when they decompose.

Harmful algal blooms seem to be multiplying in part because of what people are putting into the waterways: phosphorus run-off from agriculture; excess nitrogen from wastewater treatment plants, and septic tanks seeping into the water table; invasive zebra mussels in the Great Lakes that change the balance of algae species in the water by selectively avoiding toxic algae. Climate change adds to the problem, warming up water to bloom-comfortable temperatures earlier and longer, and changing the frequency and intensity of summer storms so that normally-sedentary algae are stirred up from lake bottoms into the surface light where they can bloom.

Chemical imbalances in water bodies throw entire ecosystems out of balance, making them less resilient to the harmful effects of algal blooms. Environmental organizations on coastal waterways plant eelgrass and oysters to try to bring back some resilience. But eelgrass, oysters, and dozens of other beneficial species, are very sensitive to the kinds of pollution that helps harmful algal blooms thrive. Many eelgrass and oyster restorations fail because the pollutants return, or the source was never truly eliminated in the first place. Conservationists and clean water defenders will keep planting, and then replanting as long as these pollutants continue to flow into waterways.

The good news is that folks are waking up to their role in shutting off the pollutants that contribute to algae blooms. Farmers in Ohio, where the Lake Erie bloom choked Toledo's drinking water, are going to fertilizer applicator school, and planting cover crops to limit the excess phosphorus that runs off of fields. And towns all along the coast are raising the local standards for septic tanks, and considering building water treatment facilities to better handle the human waste that leaks nitrogen into the water. Harmful algal blooms won't go away entirely—they're still a natural phenomenon—but at the very least, we can hopefully cut down, and maybe eliminate, blooms where human activity is to blame.

 

About Erin Gettler
Erin Gettler is a writer, photographer and naturalist living on Long Island, New York. She likes long walks in the woods, but she's too slow for real hiking on account of stopping to look at every little thing. She travels with a sketchbook, and keeps a spare pair of binoculars to share.