Coastal Runoff Killing Underwater Gardens.

• Position: Coral reefs - Brief Article

Deep beneath the waters of the Gulf of Mexico, scientists in scuba gear from The University of Texas at Austin have planted an odd-looking garden. The "crop" consists of watertight Ziploc bags full of seaweed collected from a nearby coral reef. The bags also contain various amounts of nitrogen and phosphorous, the same kinds of nutrients that make lawns, flowers, and food crops flourish.

The translucent packages are attached by a 6'x 6' square polyvinyl frame with aluminum poles. Light reaching the bags through the water is continuously measured utilizing light meters. After about eight hours, the frame is retrieved; the seaweed (or macroalgae) is harvested; and the scientists are ready to continue their experiments at the next location.

This strange activity is a part of the worldwide effort to protect and learn more about the colorful colonies of minute creatures that make up the Earth's underwater gardens --coral reefs. Coral are a combination of plant and animal, tiny polyps that build shells around their bodies, no more than a millimeter to several centimeters in size, and zooxanthellae, a microscopic form of algae that live in the polyp's tissue, providing its intense colors.

Scientists believe that coastal runoff, including everything from lawn fertilizers to sewage, spurs the growth of macroalgae, which look like large red, brown, and green plants. They can grow so much they block light needed by zooxanthellae, eventually killing coral and turning the once rainbow formations deathly white. Kenneth H. Dunton, a research scientist and associate professor at the university's Marine Science Institute at Port Aransas, explains that, when large...