Summer has traditionally meant it’s time to pack up the kids and head to the lake for swimming, boating, and fishing.

But that’s all changing as toxic blue-green algae, also called cyanobacteria, spreads across a growing number of U.S. lakes.

The once-fresh lakes reek like outhouses. The smell alone can cause respiratory problems and headaches. | Credit: Photo by Peg McAloon.

The green slime hurts tourism and property values and is changing many family traditions.

"My family has spent every 4th of July on Grand Lake St. Marys. The last three years we haven't been able to go swimming because of the algae. It puts a damper on the fun." -Ron Wyss (resident)

Contact with toxic blue-green algae can make people and pets sick. Many states issue warnings to keep people out of the water.

"Health warning signs have been posted for the last three years, eliminating any possibility of my grandchildren, family, and friends enjoying the lake with me." -Bill Ringo, Grand Lake St. Marys

“I get sick breathing the air in my own home. In the summer we have to keep all the windows closed or leave town because of the toxic fumes coming off the lake.” -Peg McAloon (resident)

The algae can also kill or sicken dogs and pets. State health departments warn pet owners to keep dogs away from toxic blooms.

What causes green slime? Though sewage and wastewater play a role, chemical fertilizer and manure are the biggest culprits, running off farms into waterways. | Credit: Photo by Lynne Betts, NRCS.

That same pollution also creates the dead zone in the Gulf of Mexico. Algae grows there too, sucking up oxygen so fish flee and sea life can't survive.

Heat and drought worsen algae growth during the height of summer tourism season. Lake area business owners suffer. | Credit: Photo by WSJ Corporation.

"I’ve been told by several people, ‘Frank, we love your place, but we’re not going to allow our children into the water, so we’re not going to be back.’” -Frank Rybeck (resort owner) | Credit: Photo courtesy of River Alliance of Wisconsin.

"I was the biggest developer on Grand Lake St. Marys for 20 years. When the blue green algae hit three years ago, my sales stopped and I had to file bankruptcy." -Steve Klosterman (developer)

"Last year, families came to fish for a week and would leave after two days due to the algae. That’s money leaving Ohio and not coming back." -Rick Unger (charter boat captain) | Credit: Photo courtesy of Ohio Sea Grant.

Farm practices can be used to minimize fertilizer use and reduce runoff. But these are voluntary practices, used by a minority of farmers. | Credit: Photo courtesy of Midwest Environmental Advocates.

"There are many tools that we use to protect the water that leaves our farms. We plant buffer strips and perennials on steep slopes to prevent erosion." -Jerry Peckumn (farmer)

Wisconsin law rewards farmers for practices that protect water, but Gov. Walker sought to repeal and delay implementation. Now the EPA has stepped in to enforce the Clean Water Act. | Credit: Photo by Bob Nichols / NRCS.

Programs that encourage water-friendly practices have been cut from the 2012 Farm Bill. With the future of our lakes at stake, conservation farming practices should be the norm.

Algae keeps spreading. To learn more, follow #greenslime on Twitter.