July 10, 2009 What's That Thing in the Meer? Solar-powered water circulators help keep algae under control in the Harlem Meer      If you’ve strolled through the north end of Central Park over the last week, you may have done a double take upon passing Harlem Meer. Your eyes aren’t deceiving you. There is, indeed, a pair of peculiar-looking devices floating atop the 11-acre water body.      Called SolarBee, the units “landed” in late June. Odd as they may appear, they’re actually doing the Meer a whole lot of good. The devices are floating solar-powered circulators that eliminate the pesky blue-green algae blooms that leave the water murky and muddled with aquatic weed. The result is clean, clear water and a healthier habitat for fish.      It works like this: Using solar-generated power, the units create a convection current to pull the deepest water of the Meer to the surface and push the surface water below. The recirculation increases oxygen in the water while disrupting the blue-green algae’s habitat, thus its ability to grow. Another plus? The technology allows the Central Park Conservancy to improve the Meer’s water quality without the use of toxic chemicals. The Algae Issue      So why are the Park’s freshwater bodies so troubled by algae in the first place? It’s not easy to pinpoint one single factor. Water temperature, light penetration, run-off, oxygen and pH levels — all play a role in how fast and widespread blue-green algae will grow. All are also very difficult to control individually. In the past, the Conservancy tried to harvest and compost the algae. While it sounds like a practical solution, the method actually proved far too labor intensive, requiring constant maintenance of the Meer and the necessary machinery.      The SolarBee is certainly not a panacea, but the Conservancy is eager to see its results and will be monitoring its progress through water quality testing and observation.      The SolarBees made their way to the Meer after the Parks Department, aware of the algae issues in Central Park’s freshwater bodies, approached the Conservancy about testing out the devices over a free trial period. The Conservancy agreed, always looking to explore new technologies that enhance the Park’s diverse landscapes while reducing labor and wear on machinery.      Now, the two machines — the largest of SolarBee’s models — will circulate a combined 38.8 million gallons of water each day.      While the technology has proven effective in freshwater bodies in other cities, the improvements won’t surface overnight. With the algae so widespread, the devices are expected to be operating in the Meer for at least two years.