Jellypocalypse Is Upon Us

A Japanese fishing trawler capsizes off Chiba` and its three man crew is thrown into the sea. The cause? Gigantic Nomura's jellyfish. Around the world, sightings of jellyfish blooms have lead to charges that climate change is clogging the ocean with hoards of gelatinous creatures. Is Jellypocalypse truly upon us? Is an incensed mother nature striking back by unleashing a plague of pulsating, tentacled monsters? Before chalking up yet another natural disaster to the dreaded anthropogenic global warming it would be best to consider a new report in the Proceedings of the National Academy of Sciences.

It sounds like something out of a B-grade horror film, not real life. A sea filled with pulsating, 450lb jellyfish inflicting damage on the Japanese fishing fleet, terrorizing the fishermen. The crew of one fishing boat thrown into the sea when their vessel capsizes, with the three men having to be rescued by another trawler. The widely reported trawler incident happened back in 2009, but is cited by many as one in an increasing number of jellyfish related incidents over the past decade.

This is not the first time Japanese fishermen have been accosted by Nemopilema nomurai—commonly known as Nomura's jellyfish. One of the largest jellyfish in the world, the species can grow up to 2 meters in diameter. The last time Japanese waters were invaded on a similar scale, in the summer of 2005, the jellyfish damaged nets, caused injuries to fishermen, and rendered fish inedible with their toxic stings. They are an unwelcome sight to say the least.


Fishermen vs. giant jellyfish off Japan's coast.

Naturally, the mainstream climate change complicit press try to create circumstantial links to global warming. “One strand of evidence for the deterioration of Earth's oceans is the perception that the seas are becoming overwhelmed by jellyfish,” trumpets an editor's choice article by Caroline Ash in Science, with the nicely alliterative title “Pulsing Populations of Jellies.” Spreading a little fear and doubt, her piece concludes “the jury is still out on whether jellyfish will take over the increasingly anthropogenically affected oceans.”

According to R. H. Condon, of the Dauphin Island Sea Lab, “There’s a perception that jellyfish numbers are exploding in the world’s oceans, but there’s no real evidence for a global increase in jellyfish over the past two centuries.”

Condon is one of a collection of scientists known as the Jellyfish Group. Together they have published a study in PNAS titled “Recurrent jellyfish blooms are a consequence of global oscillations.” Condon et al. undertook a meta-analysis using linear and logistic mixed models and effect-size analysis on data ranging from 1790 to 2011. Though available data is sparse, there is reason to believe that the occasional jellyfish outbreaks reported from around the world are not out of the ordinary. The report's abstract sums up the investigators' conclusions:

A perceived recent increase in global jellyfish abundance has been portrayed as a symptom of degraded oceans. This perception is based primarily on a few case studies and anecdotal evidence, but a formal analysis of global temporal trends in jellyfish populations has been missing. Here, we analyze all available long-term datasets on changes in jellyfish abundance across multiple coastal stations, using linear and logistic mixed models and effect-size analysis to show that there is no robust evidence for a global increase in jellyfish. Although there has been a small linear increase in jellyfish since the 1970s, this trend was unsubstantiated by effect-size analysis that showed no difference in the proportion of increasing vs. decreasing jellyfish populations over all time periods examined. Rather, the strongest nonrandom trend indicated jellyfish populations undergo larger, worldwide oscillations with an approximate 20-y periodicity, including a rising phase during the 1990s that contributed to the perception of a global increase in jellyfish abundance.

Jellyfish are members of the phylum Cnidaria, a marine group of structurally simple aquatic animals. There are both fixed and mobile animals in the group. Sea anemones, sea whips, corals and hydroids are polyps that grow attached to rocks or other hard surfaces. Free floating jellyfish and colonial siphonophores like the Portuguese man-of-war are mobile and either actively swim or drift with the winds and currents.

Among some of the oldest forms of multicellular life jellyfish have been around for 650 million years, predating the Cambrian period that saw complex life explode across Earth. This implies that they have survived when earthly temperatures were much warmer than today's and much colder. Today, jellyfish inhabit every major oceanic area of the world and are capable of withstanding a wide range of temperature and salinity. Most live in shallow coastal waters, but a few inhabit depths of 12,000 feet. This qualifies jellyfish as one of nature's top evolutionary successes.


Life without a brain, one of nature's success stories.

Instead of a brain, jellyfish possess an elementary nervous system, or nerve net, which consists of receptors capable of detecting light, odor and other stimuli and coordinating appropriate responses. As Jimmy Buffett sang in his song “Mental Floss”:

They're Just Simple Protoplasm
Clear As Cellophane
They Ride The Winds Of Fortune
Life Without A Brain

Condon et al. are careful to note, that while the case for exploding jellyfish populations is overstated, that doesn't mean jellyfish populations are not increasing. But there is no strong long-term evidence they are doing so at an unnatural rate. Although strong 20-year oscillations were revealed by their analysis, only a weak upward trend has been observed since 1970. Even so, the authors have this warning for agitated jellyfish watchers everywhere: “our findings foretell recurrent phases of rise and fall in jellyfish populations that society should be prepared to face.”

It would appear that cries of “Jellypocalypse” are premature at best—it is just the humble jellyfish doing what they have been doing since before the Phanerozoic Eon began. Simply another example of the blame-humanity-for-every-bad-natural-occurrence crowd's jumping to conclusions. Yet those who see the climate change bogeyman hiding behind every unexpected act of nature should take heart. As the simple jellyfish proves, life is possible without a brain.

Be safe, enjoy the interglacial and stay skeptical.