In the May issue of Deep Sea Research, scientists report that salps, about the size of a human thumb, swarming by the billions in “hot spots” may be transporting tons of carbon per day from the ocean surface to the deep sea and keep it from re-entering the atmosphere.

Salps are semi-transparent, barrel-shaped marine animals that move through the water by drawing water in the front end and propelling it out the rear in a sort of jet propulsion. The water passes over a mucus membrane that vacuums it clean of all edible material.

The oceans absorb excess carbon dioxide from the atmosphere, including some from the burning of fossil fuels. In sunlit surface waters, tiny marine plants called phytoplankton use the carbon dioxide, C02, to grow. Animals then consume the phytoplankton and incorporate the carbon, but most of it dissolves back into the oceans when the animals defecate or die.

The carbon can be used again by bacteria and plants, or can return to the atmosphere as heat-trapping carbon dioxide when it is consumed and respired by animals.

Researchers found that one particular salp species, Salpa aspera, multiplied into dense swarms that lasted for months. One swarm covered 100,000 square kilometers (38,600 square miles) of the sea surface. Their sinking fecal pellets transported up to 4,000 tons of carbon a day to deep water. The scientists also showed that when salps die, their bodies also sink fast?EUR??,,????'??+up to 1,575 feet a day, far faster than most pellets.

If salps are really a dead-end in the food web and remain uneaten on the way down, they could send even more carbon to the deep.