Jellyfish Blooms Upend Marine Food Webs

Photo courtesy: Jaymi Heimbuch/Creative Commons

Jellyfish are taking over the world's oceans. Warming waters and the elimination of key predators like sharks and tuna, have made conditions ideal for the soft, brainless, organisms and their numbers have increased steadily for years—with populations occasionally exploding in "blooms."

Now, new research shows that jellyfish are upending marine food webs—and disrupting ocean ecosystems' ability to sync carbon in the process.

The problem is that jellyfish are voracious predators that consume plankton rapidly and in huge quantities. This effectively prevents small fish from finding the food the need to thrive, collapsing an important low-ring of the chain. "This restricts the transfer of energy up the food chain," explained Rob Condon, who led the study, "because jellyfish are not readily consumed by other predators."

Photo courtesy: Jaymi Heimbuch/Creative Commons

Moreover, jellyfish have a significant impact on marine bacteria, which play an important role by recycling key elements and nutrients created by decaying organisms back into the food web. When fish die and are broken down, the bacteria absorb carbon, nitrogen, phosphorus, and other byproducts. When jellyfish die, a different process takes place.

Condon's research found that decaying jellyfish produce organic matter that is intensely rich in carbon—too rich, he believes, for bacteria to use it for growth. Instead, he discovered, bacteria in jellyfish-infested waters dispose of carbon through respiration—a process that returns much of the element to the atmosphere in the form of carbon dioxide.

The presence of this carbon-rich food source did not only increase carbon dioxide emissions, however, it also led to an increase in the population of microbes that were once rare in the areas researched. This finding, Condon says, shows that jellyfish blooms are not only changing the function of food webs but their form—at a fundamental level—as well.

"If these swarms continue to emerge," he explained, "we could see a substantial biogeochemical impact on our ecosystems."

Via TreeHugger