Red Tides Threaten Beaches
Floating blankets of toxic algae could force more beach closures.
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Used to be one of the only things that could spoil a day at the beach was an unexpected thunderstorm. But now a new threat to beach fun -- huge, floating blankets of red algae known as red tides -- could become a more frequent killjoy.
During a red tide, oxygen-consuming, toxic algae cover huge swaths of ocean. Fish, sea turtles, whales, and dolphins have all washed up dead onto beaches, with red tide a suspected cause. For people, just breathing in the vicinity of a red tide can trigger asthma episodes, coughing and throat irritation. Many residents of coastal communities find the effects insufferable. For them, even staying indoors does not solve the problem. Also, eating shellfish exposed to a red tide can cause digestive problems.
Red tides sometimes occur naturally, but human activity -- including pollution and overdevelopment along coastlines -- could be making them more frequent and more severe.
One of the worst incidents in recent years occurred along the Gulf Coast of Florida in 2005. There, red tides are annual events, often lasting several months at a stretch. But 2005's red tide lasted an entire year, and grew to cover 26,000 square miles of water -- an area larger than the state of West Virginia. "There’s not one living thing out here -- nothing," a tour boat captain told The Miami Herald. "The only thing I see breaking the surface is dead fish."
A red tide also swept across New England coastal waters in 2005, prompting officials to close large areas to shellfishing at the height of the tourism season. The economic loss to Massachusetts was tabulated at $15 million. In some areas, shellfishing wasn't safe for a year after the event.
Scientists are working to pinpoint the exact relationship between red tides and human activities. The tides have been linked to high amounts of nutrients in the water -- which come from inadequately treated sewage, manure from industrial farming, and fertilizer runoff from crops and yards. Overdevelopment along coastlines and in watersheds also causes nutrient pollution. Shellfish play a critical role, too, because they filter water. When scallops, clams, oysters and other shellfish are depleted by overharvesting, the ecosystem can't cleanse itself of toxic algae as efficiently. Coastal wetlands also filter pollution, and their loss to development may exacerbate red tides. Finally, water arriving from around the world as ship ballast can spread red tide.
The good news is that the human activities suspected of exacerbating red tides can be addressed -- with more sensitive development on our coastlines, better stewardship of waterways, wetlands, and shellfish populations, and a tighter rein on water pollution coming from farms, sewage treatment plant discharges, and storm water that runs off of paved urban areas. Scientists who study red tides also need more support to fully understand how red tides are caused, and the best ways to address the problem.
