Jellyfish also shunt food energy away from fish and shellfish that humans like to eat through their effects on the bacterial community.
"Marine bacteria typically play a key role in recycling carbon, nitrogen, phosphorus and other by-products of organic decay back into the food web," says Condon.
"But in our study, we found that when bacteria consumed dissolved organic matter from jellyfish they shunted it toward respiration rather than growth."
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 matter--with 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 percent."
|Contact: Cheryl Dybas|
National Science Foundation