The following are guest posts from undergraduate students in the Marine Ecology class that I am a TA for this semester. See the entire student blog at http://marineecologyblog.web.unc.edu/
By Katie Myrick and Olivia Wilson
Cue Jaws theme song…but instead of it being an unrealistically huge shark that you have to worry about, it’s jellyfish. Swarms of them. Some of them as big as 200kg (that’s 440lbs for all of us American ‘nonconformists’). The worst part? You can’t roll over and wake up or turn the TV off on this one. It’s happening. Over the last decade, ocean-goers and researchers have been noticing an increase in the number of jellyfish invasions worldwide. Power plants have been forced to shut down because of jellyfish clogs in their water intake systems, and unfortunately, it’s not because a group of environmentally-conscious jellies decided to stage a protest—the cnidarians don’t have brains. It is, however, an unconscious response by the jellyfish to environmental exploitation.
Overfishing has severely reduced the prevalence of a lot of the major competitors for organisms at lower trophic levels. This means that not only have the jellyfish been largely released from predation and population size constraints, but that the organisms that they eat have too. The combination of reduced competition and increased food availability allows for surges in jellyfish population size. The problem is exacerbated by the fact that flexibility in marine trophic organizations allows for jellyfish predation upon the larvae of their future predators, initiating a downward spiral effect1.
The only way to remedy these problematic indirect effects of overfishing would be to—you guessed it!—STOP OVERFISHING. The best place starting point would be limitation of large fish catch, which would increase jelly predation while simultaneously increasing the productivity of big-fish populations. Alternatively, this might be the perfect time to give SpongeBob a call!