Limnol. Oceanogr. 54, 1197–1209 (2009)

Credit: NICK HOBGOOD

Common jelly-like creatures known as pyrosomes transport vast amounts of carbon to the sea floor, finds a new study. The research by Mario Lebrato and Daniel Jones of the National Oceanography Centre at the University of Southampton, UK, provides new evidence of the importance of gelatinous zooplankton in the marine carbon cycle.

Lebrato and Jones used a remotely operated vehicle equipped with underwater video cameras to survey the sea floor off the Ivory Coast of west Africa after the mass deposition of thousands of pyrosome carcasses between February and March 2006. The creatures piled up on the sea bed, in some regions exceeding 4,000 per 100 square metres. The researchers found that carbon constituted a third of the body mass of sampled carcasses, exceeding previously recorded levels in any gelatinous creature. They estimate that the pyrosomes contributed more than 5 grams of carbon per square metre — and in some cases as much as 22 grams per square metre — to the seabed in the studied area, which covers over 13,000 square metres.

Eight types of animal, together with bacteria, were found feeding on the carcasses, suggesting that gelatinous carbon is a key — and previously unappreciated — component of the marine food web off the Ivory Coast. The authors say that pyrosome carcasses probably have an important role in transporting carbon from the sea surface to the sea floor across the globe.