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Giant balls of mucus fertilize the ocean

June 9, 2005 By Nicola Jones This article courtesy of Nature News.

Jelly creatures help solve mystery of carbon supply to the sea floor.

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The discarded mucous houses of tadpole-like sea creatures called larvaceans have been revealed to be a major source of food for seafloor life.

Scientists have long wondered about the origin of the food eaten by creatures that live near the ocean floor. Carbon from the remains of dead fish, plankton and other detritus of marine life is known to trickle down through the water. But measurements have indicated that this slow 'rain' of particulates is not enough to sustain the life below.

So Bruce Robison and his colleagues from the Monterey Bay Aquarium Research Institute in Moss Landing, California, wondered if larvaceans (also known as appendicularians) might make up the difference. These creatures, which can be up to 6 centimetres long, feed themselves by creating a giant filter sack of mucus that can reach up to a metre in length. They pump water through this sack with their tails, and feed on the captured carbon.

They become great big, carbon-rich, fast-moving particles the size of your fist that shoot to the deep sea floor
Bruce Robison
Monterey Bay Aquarium Research Institute, California
When the filters become clogged, the larvacean discards its house and excretes a new one. The old house will sometimes collapse into a ball laden with carbon that plummets through the water. "They become great big, carbon-rich, fast-moving particles the size of your fist that shoot to the deep sea floor," says Robison.

By measuring this process in the Monterey Bay area over ten years, Robison concludes that the creatures supply 7.6 grams of carbon to each square metre of Monterey sea floor in a year. That's half as much again as the carbon provided by the slow trickle of marine particulates, and is more than enough to account for the 'missing' food.

"The carbon content of these particles is a major percentage of what gets down there," says Robison, whose results are published in Science1. He adds that the same creatures are probably contributing carbon to the sea floor in other warm-water areas.

Larvaceans and jellyfish are typically hard to study, because their delicate bodies are often cut up instead of being retrieved by nets. But as researchers learn more about them, they have found these creatures contribute much more to the marine cycle than previously appreciated.

If you are a subscriber, you can read more about jellyfish and larvaceans in our feature, 'Close encounters of the jelly kind'.

References

  1. Robison B., Reisenbichler K., Sherlock R., et al. Science, 308. 1609 - 1611 (2005).

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