Transparent Animals May Play Overlooked Role in the Oceans

Article excerpt

Salps don't get much respect. They've been around for millions of years, but hardly anyone even knows they exist.

Even many who have heard about these transparent, jellylike creatures consider them a dead end in the ocean food web: They cruise around, vacuuming up microscopic plants, but don't get eaten by other animals, making them a marine equivalent of inedible cows.

But in the May issue of Deep-Sea Research, scientists report that salps may play an important and overlooked role in determining the fate of the greenhouse gas carbon dioxide in the ocean. Swarming by the billions in salp "hot spots," they transport tons of carbon per day from the ocean surface to the deep sea and keep it from re-entering the atmosphere, the scientists say.

Biologists Laurence Madin of Woods Hole Oceanographic Institution (WHOI) and Patricia Kremer of the University of Connecticut led researchers to the Mid-Atlantic Bight region (between Cape Hatteras and Georges Bank) in four summers since 1975, and each time found that one species, Salpa aspera, multiplied into dense swarms that lasted for months.

One swarm covered 38,600 square miles (100,000 square kilometers) of the sea surface, containing perhaps trillions of thumb-sized salps. The scientists estimated that the swarm consumed up to 74 percent of microscopic carbon-containing plants from the surface water per day, and their sinking fecal pellets transported up to 4,000 tons of carbon a day to deep water.

The oceans absorb carbon dioxide from the atmosphere, including some of the carbon dioxide emitted by fossil-fuel burning. In sunlit surface waters, tiny marine plants--phytoplankton--use it to grow. …