Much Ado About Jellyfish

Experts Question Claims About Surging Populations

Adult Moon Jelly

In 2008, a massive influx of jellyfish disabled the Diablo Canyon nuclear power plant in San Luis Obispo County. Last summer, four nuclear power plants — in Israel, Japan, Scotland, and Florida — also had to shut down operations due to swarming jellyfish. Coastal reactors suck in ocean water to use for their cooling systems, filtering out marine life and debris with devices called flumes. The sheer number of jellyfish near the affected plants proved to be more than the flumes could handle, blocking the flow of cooling water to the plants’ nuclear reactors, causing shutdowns across the globe.

One cannot help but wonder if, due to overharvesting of fish and other natural predators, plus increasing ocean temperatures due to climate change, human activity has caused an explosion in global jellyfish populations. Global experts, in a recent study, have said that there is no evidence that this is the case.

Conducted at UCSB’s National Center for Ecological Analysis and Synthesis (NCEAS), this study, led by Rob Condon of the Dauphin Island Sea Lab in Alabama, concludes that claims that jellyfish are increasing worldwide are not supported with any hard evidence or scientific analyses. These results have been published in the latest issue of the journal BioScience. Working alongside Condon were coprincipal investigators Carlos Duarte of the University of Western Australia’s Oceans Institute, and Monty Graham of the University of Southern Mississippi, along with experts from the Global Jellyfish Group — a consortium of approximately 30 experts on gelatinous organisms — climatology, oceanography, and socioeconomics from around the globe.

Large groups of jellyfish, called blooms, have undoubtedly been appearing all over the world. A notable case is on the western coast of Japan where, in recent years, hoards of titanic jellyfish — some over six feet long and weighing upward of 400 pounds — have been spotted. These giant jellyfish were first spotted in the early 20th century, but, since 2002, populations have been increasing dramatically.

This is most likely due to a nearly two-degree Fahrenheit increase in temperature of the waters off China’s coast as well as a decrease in local sea turtle and fish populations, making conditions ideal for breeding. This has resulted in instances such as a 10-ton fishing boat sinking after dozens of giant jellyfish were caught in their nets back in 2009. “Clearly, there are areas where jellyfish have increased — the situation with the giant jellyfish in Japan is a classic example,” Condon said in a press release, “but there are also areas where jellyfish have decreased or fluctuated over the decadal periods.”

According to Condon, looking at the long-term rather than short-term data is the key to understanding jellyfish blooms. The problem is that, so far, there has been no way to collect and aggregate data. “The scientific data exists to answer this question, but it is fragmented in analysis,” Condon said. The researchers came up with a solution to this with what they call the centerpiece of their collaboration with NCEAS: the Jellyfish Database Initiative, or JEDI. “This is the first time an undertaking of this size on the global scale has been attempted, but it is important to know whether jellyfish blooms are human-induced or arise from natural circumstances,” said Condon. “The more we know, the better we can manage oceanic ecosystems or respond accurately to future effects of climate change.”

The global analyses using JEDI are currently in progress. They anticipate finishing in spring this year.


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