The upshot of this "jelly carbon shunt" is that bacteria in jelly-laden waters end up converting carbon back to carbon dioxide, rather than using it to grow larger or reproduce. This means the carbon is lost as a direct source of organic energy for transfer up the food web.
The researchers think the shift toward bacterial respiration happens because jellyfish produce organic matter that is extra rich in carbon. They do so through excretion and the sloughing of mucus. "The mucus is the slime you feel when you pick up a jelly," says Steinberg.
The jellyfish in Condon's experiments released large quantities of carbon-rich organic matterwith 25- to 30-times more carbon than nitrogen. That compares to a ratio of 6 parts carbon to 1 part nitrogen for the organic matter found dissolved in typical marine waters.
"The bacteria metabolized this carbon-rich material two to six times faster than they did with dissolved organic matter from water without jellyfish," says Condon. "This rapid metabolism shunted carbon toward respiration rather than production, reducing their potential to assimilate this material by 10% to 15%."
Steinberg says that bacterial metabolism of dissolved organic matter from jellyfish is like "drinking Gatorade" while metabolism of dissolved organic matter from phytoplankton and other sources is like "eating a hamburger." "It just doesn't provide an efficient food source for marine bacteria," she says.
The Microbial Community
A final significant finding from the team's research is that an influx of dissolved organic matter from jellyfish blooms changes the make-up of the local
|Contact: David Malmquist|
Virginia Institute of Marine Science