Painful but important lessons from jellyfish

Nothing is going to put you off a dip in the sea faster than a seething soup of jellyfish.

Painful stings for swimmers, clogged nets for fishermen, even blocked cooling intake pipes for power plants are just some of the negative impacts of jellyfish blooms around the world.

But recent concerns that our oceans are experiencing an explosion in jellyfish numbers are unfounded according to Dr Kylie Pitt.

Dr Pitt has taken part in a multinational collaborative study which has found no strong evidence of global increase in jellyfish populations over the past two centuries.

“Instead, the key finding of this research was that global jellyfish populations undergo natural fluctuations, including a rising phase in the 1990s and early 2000s that has contributed to the current perception of a global increase in jellyfish abundance,” Dr Pitt said.

“The previous period of high jellyfish numbers during the 1970s went relatively unnoticed due to limited research on jellyfish at the time.

Thirty international experts took part in the study led by Dr. Rob Condon, a marine scientist at the Dauphin Island Sea Lab (DISL) in Alabama.

Dr Condon said regional blooms have added to the perception that the number of jellyfish are on the rise everywhere.

“Clearly, there are areas where jellyfish have increased. The situations with the Giant Jellyfish in Japan, and parts of the Mediterranean are classic examples,” Dr Condon said.

“But there are also areas where jellyfish numbers have remained stable, fluctuated over decadal periods, or actually decreased over time.”

The results of the study have been published in the article “Recurrent Jellyfish Blooms are a Consequence of Global Oscillations” in the latest issue of Proceedings of the National Academy of Science (PNAS manuscript # 2012-10920R).

“What is important now is that monitoring is sustained over the next decade to determine if there really is an increasing trend in jellyfish populations after 1970 or if it is just part of a larger oscillation,” Dr Pitt said .

“Given the potential damage posed by jellyfish blooms to fisheries, tourism and other human industries, it is important from a management perspective to understand and therefore anticipate these recurrent phases of jellyfish ecology.”