Summer was officially over last week and it was some summer in the Greater New York Area: record hot and a summer—and this is related—in which we were hit with loads of jellyfish off Long Island, where I live.
It used to be that jellyfish would arrive in these parts in August—when the waters off our shores had become sufficiently warm. But again this year, those stinging globs were here in June and by July there were swarms of them, remaining through August.
This jellyfish explosion here is mirrored around the world. With global warming a prime culprit, there’s been the revenge of the jellyfish for those who love the water all over this earth.
“There has been a global increase in jellyfish with the higher temperatures of recent years,” explains Dr. Christopher Gobler, associate professor at the School of Marine and Atmospheric Sciences at New York’s Stony Brook University. “With global warming, jellyfish emerge earlier, grow quicker and stay around longer.”
He notes other factors, too—also having to do with the activities of people.
There’s eutrophication, the process in which water bodies receive excess nutrients. Algal blooms are triggered by eutrophication, Dr. Gobler notes, and the blooms “reduce oxygen and water clarity. These conditions have adverse effects on planktivorous fish [fish that eat plankton] meaning the fish consume lower amounts of plankton. Because jellyfish are non-visual predators and are less sensitive to low oxygen” they can feast on the plankton that the planktivorous fish are missing. Jellyfish “thrive under these conditions.”
Then there’s overfishing. “The overharvest of filter feeding bivalves and planktivorous fish such as menhaden leaves more plankton for jellyfish to consume,” says Dr. Gobler.
And there is what’s termed “shoreline hardening—the building of bulkheads, docks and jetties which encourages greater jellyfish populations because jellyfish polyps attach to these “hard surfaces” and “we have more of these now,” says Dr. Gobler.
What was termed a worldwide “jellyfish plague” was examined a while back by the British magazine, New Scientist, in an article -- http://www.newscientist.com/article/mg19626323.700-insight-overfishing-is-creating-a-jellyfish-plague.html -- that began: “Global warming is starting to sting—literally.” The story by Debora Mackenzie told of how warmer water caused by global warming has resulted in mammoth swarms of jellyfish—such as one 20 square miles in area, 33 feet deep in the Irish Sea that hit a salmon farm “killing all 100,000 fish in it.
The piece also linked the increased levels of carbon dioxide being released on the planet—central to global warming—to the jellyfish explosion. The CO2 discharges are causing seawater to become more acidic. This has been harming “small creatures with acid-soluble shells that compete with jellyfish.”
It stressed overfishing, and what was described as “a vicious cycle” was outlined. “Overfishing means we need more fish farms and it also boosts populations of jellyfish which damage fish farms,” it related. “As the growing human population needs more food, that exacerbates warming, and…jellyfish prosper. The final irony: small plankton-eating fish, which compete most directly with jellyfish” are being “overfished—largely to make fishmeal, the main food for fish farms.”
The article stated: “Fisheries scientists have warned for years that we are replacing an ocean full of fish with one full of jellyfish.”
Wow, what an aquatic mess.
Now with due respect to those in the Orient who like to eat jellyfish, I must say I don’t like them at all—I can’t imagine eating them and I don’t like swimming around them.
Considering that humans are the prime culprits when it comes to the conditions that have created the huge uspsurge in jellyfish, it’s obvious that we must change course, and fast. The jellyfish explosion is sending us a very clear message.