More than two years ago, Activist Angler began telling you about the growing number of jellyfish “blooms” in our oceans. (Here’s a link to one of those posts.)
Some scientists think that the decline of jellyfish predators (sea turtles, as well as some species of fish) specifically and the decline of fish populations generally are allowing jellyfish to thrive and spread as never before.
But the fact that this phenomenon coincides with an increasing frequency of troublesome alga blooms in freshwater suggests something more is going on.
And that something more likely is pollution. Both types of these blooms thrive in nutrient-rich water, and we provide these nutrients from sewage discharges and runoff laced with fertilizers and manure from farm lands.
In the way of an update on this problem, I refer you to a recent article at ABC News: "Monsters of the Deep: Jellyfish Threaten the World’s Seas."
Following are a couple of excerpts.
It isn't just a problem in the Mediterranean, but worldwide. Especially in late summer, swimmers in the North and Baltic Seas often encounter lion's mane jellyfish, which are known as "fire jellyfish," and for good reason. Their stringy stinging tentacles are often the color of flames. Far more common in the region are blooms of milky-blue moon jellyfish, which, like the majority of jellyfish species, do not inflict pain on human beings.
Compass and crystal jellyfish now dominate the coastal waters of Namibia, where sardines were once abundant. And since the mid-1990s, fishermen in the East China Sea and the Yellow Sea have complained that their nets are being filled with more and more jellyfish and fewer and fewer fish.
A species prevalent in Japanese waters could provide the material for a horror film: the giant Nemopilema nomurai, or Nomura's jellyfish, with a bell diameter of up to two meters (6 feet, 6 inches). In the last century, there were only three population blooms of the species, in 1920, 1958 and 1995. But Japanese scientists report that the Nomura's jellyfish has invaded Asian waters almost every year since 2002, with only two light years in the interim: 2004 and 2010. The species is so heavy that large numbers caught in nets can capsize fishing vessels.
What does all of this signify? Why are the seas becoming jellified?
Gili wrinkles his brow. "The jellyfish are a message in a bottle that the sea is depositing on our beaches," he says. The ocean's message to mankind, he adds, is simple: "You are destroying me."
Costly and Harmful
The fact that human beings and jellyfish tangle with one another more frequently than in the past is unpleasant for both sides. It also costs many millions each year, although the exact costs are difficult to estimate. For instance, jellyfish often cause power outages and equipment damage when they enter the cooling water systems of power plants and desalination plants.
Jellyfish are also harmful to fishery. They ruin nets and cause chemical burns on the hands of fishermen. If a jellyfish bloom collides with the nets that separate fish farms from the open water, the creatures' toxins can sometimes kill all of the animals in the enclosures.
And then there is the problem oceanographer Josep Maria Gili can see from his terrace: Jellyfish on the beach, coinciding with the vacation season, are a debacle for tourism. These days it is the reddish, glow-in-the-dark jellyfish Pelagia noctiluca, or mauve stinger, that lurks in the waters off Barcelona. In recent days, Red Cross paramedics have had to treat at least 400 swimmers a day for jellyfish injuries. A yellow warning flag is posted on the beach below, and a voice blaring from loudspeakers warns bathers in Spanish, French and English to be careful around jellyfish.