Experts question: Jellyfish really on the rise?

UC SANTA BARBARA (US) — Claims that jellyfish are increasing worldwide are not backed up by any hard evidence or scientific analyses, according to a new study.

Blooms, or proliferation, of jellyfish have shown a substantial, visible impact on coastal populations—clogged nets for fishermen, stinging waters for tourists, even choked intake lines for power plants—and recent media reports have created a perception that the world’s oceans are experiencing increases in jellyfish due to human activities such as global warming and overharvesting of fish.

The results of a recent study, conducted at the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California, Santa Barbara, appear in the latest issue of the journal BioScience.

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“Clearly, there are areas where jellyfish have increased—the situation with the Giant Jellyfish in Japan is a classic example,” says study leader Rob Condon, a marine scientist at the Dauphin Island Sea Lab in Alabama. “But there are also areas where jellyfish have decreased, or fluctuate over the decadal periods.”

Condon says understanding the long-term rather than short-term data is the key to solving the question about jellyfish blooms.

Increased speculation and discrepancies about current and future jellyfish blooms by the media and in climate and science reports formed the motivation for the study.

“There are major consequences for getting the answer correct for tourism, fisheries, and management decisions as they relate to climate change and changing ocean environments,” says co-principal investigators Carlos Duarte of the University of Western Australia’s Oceans Institute and the Instituto Mediterráneo de Estudios Avanzados in Spain.

“The important aspect about our synthesis is that we will be able to support the current paradigm with hard scientific data rather than speculation.”

Condon’s co-authors include experts from the Global Jellyfish Group, a consortium of approximately 30 experts on gelatinous organisms, climatology, oceanography, and socioeconomics from around the globe.

The study highlights the centerpiece of the research collaboration with NCEAS—the formation of a global database called the Jellyfish Database Initiative (JEDI)—a community-based database project that is being used in the global analysis and to test the worthiness of the current paradigm.

The database consists of over 500,000 data points about global jellyfish populations collected from as early as 1790, and will serve as a future repository for datasets so that the issue of jellyfish blooms can be continually monitored in the future.

By analyzing JEDI, the group will be able to assess key aspects behind the paradigm, including whether current jellyfish blooms are caused by human-made actions or whether we are simply more aware of them due to their impact on human activities, such as over-harvesting of fish and increased tourism.

“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,” says Condon. “The more we know, the better we can manage oceanic ecosystems or respond accurately to future effects of climate change.

“The scientific data exists to answer this question, but it is fragmented in analysis,” says Condon. The global analyses using JEDI are currently under way with an anticipated finish date of spring 2012.

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