After a decade or so of somewhat breathless warnings of a jellyfish apocalypse unfolding in the world’s oceans, new research by an international coalition of scientists suggests that the global jellyfish population may be about the same size it always was.
Rob Condon with the Dauphin Island Sea Lab was the lead researcher on a scientific paper published this week by the Global Jellyfish Group, "Recurrent jellyfish blooms are a consequence of global oscillations."
The 30 researchers in the group study all manner of gelatinous creatures, including close jellyfish relatives such as salps and comb jellies.
The group’s research shows, in a nutshell, that jellyfish experience a population surge about every 20 years, and go through several years of greater than normal abundance. Scientists documented one of the 20-year surges between about 1995 and 2004.
But not many scientists understood what was happening at the time. In fact, many scientists feared they were witnessing a steady rise in jellyfish numbers that might continue unabated, ultimately threatening the balance of the marine ecosystem. That’s where the new research by the Jellyfish Group comes into play.
“We submitted a proposal in 2009 to fund a working group to address this question of whether jellyfish are increasing globally. Up to that time, there was no data to support this hypothesis that jellies were increasing in abundance,” Condon said.
Instead, there were a lot of media reports of spectacular jellyfish blooms, some so large they clogged industrial water intakes and forced factories and even a Scottish nuclear plant to shut down.
For its analysis, the jellyfish group gathered all the previous research they could find. The data stretch back more than 100 years. The oldest data was collected in 1874. The picture that information paints shows a fairly consistent population jump every 20 years.
“It comes down to frame of reference. What are you comparing? One year of jellies to another year? If you are comparing three or four years, our analysis shows that is not enough,” Condon said.
“There is a rising phase, and a falling phase. If you look beginning at 1990, you see a rising phase. That’s when people were seeing this increase in jellies that lasted for ten years. Then there was a falling phase.”
One of the most fascinating aspects of the research is that the rising phases affect jellyfish all around the globe. Populations rise in all of the world’s oceans at the same time.
“These natural cycles are not uncommon in nature. If you look at cicadas, cicadas are on a 17 year cycle. If you look at tree ring growth, some of the trees have these 18 to 20 year growth spurts,” Condon said. “These cycles are actually quite common. The question now is to understand how human influences on a particular ecosystem may be influencing the natural system.”
Condon said the group’s research shows a rise in jelly numbers in the 1970s, with a much larger rise in jellyfish populations detected in the 1950s. The problem, he said, is the older data are not quite as robust as the more recent data.
Until recently, jellyfish have attracted scant attention from scientific researchers. As animals go, they are as basic as it gets, consisting of a mouth, a gut and not much else. Scientists who studied them were few and far between. That has begun to change.
The rise of the internet deserves some of the credit, Condon said. First, it helped the jelly scientists find each other. Then, when media reports of a jellyfish bloom appeared somewhere, word spread quickly among the scientific community.
“We used to depend on the telephone and snail mail. Now, if we see something happening, we tap it out on Twitter and people all over the world know it,” Condon said.
Locally, a jellyfish known as the night light of the sea had a major bloom this year. Overall, jellyfish numbers spiked in 2000 and 2001, then again a few years later. Scientists were most alarmed by a huge bloom of the Australian spotted jellyfish off Alabama and Mississippi. The basketball sized animals clogged shrimp nets and were so abundant in the waters of the Mississippi Sound it looked like you could use them as stepping stones to cross from one island to the next.
Moon jellyfish numbers also jumped dramatically for several years, leading to concerns that the native species might begin to damage the ecosystem by consuming the eggs and larvae of fish, shrimp and crabs.
Then, all of a sudden, after several years of giant jellyfish blooms, the numbers in the northern Gulf dropped back to normal, or in some cases, dropped below normal. The change left scientists scratching their heads.
One of the first scientists to notice that the blooms might occur on cycle of a decade or longer was Kelly Robinson, now with the University of Southern Mississippi.
Robinson hit on her discovery while working toward a doctorate in marine biology at the Dauphin Island Sea Lab. While researching the history of recent blooms in the northern Gulf, Robinson discovered that colder winters tend to lead into big jellyfish years, and that the Gulf tends to experience 8 to 10 years of high jellyfish abundance, followed by 8 to 10 years of low jellyfish numbers.
When the jellyfish group began assembling the international data, a similar pattern began to emerge.
In the end, Condon said the research suggests a slight rise in jellyfish numbers today compared to the 1970s. It is impossible to characterize how significant the rise might be without more data. It is also impossible to determine if the population rise poses a threat to marine ecosystems.
“We are not discounting that research. But we need data from at least three rise and fall cycles to begin to draw conclusions,” Condon said.
Securing funding for a research effort that will take decades is problematic, he lamented. Most science research lasts for three or four years, about as long as the average political term, not three or four decades.