A worldwide upswing in jellyfish?
So why the increase? Why now? and Why in so many places at once? They are several possible answers, pretty much all human-caused one way or another.
Once answer is climate change as felt through warming ocean temperatures, which creates a more favorable environment for jellyfish and allows them to expand their range.
Another answer is the loss of sea turtles and other jellyfish predators, permitting more jellyfish to survive. The overfishing of species which directly compete with jellyfish for food is another possibility.
Finally, sewage and agricultural runoff adds nitrogen to the water, which jellyfish thrive upon.
A couple of quotes from the Independent article above
"Jellyfish are a natural part of the marine environment, but the scale of what's happening now is a warning that something's going very wrong," says Dr David Santilo, a marine biologist for the Greenpeace research laboratories at Exeter University.
The French-Canadian biologist Daniel Pauly paints an apocalyptic vision of oceans taken over by jellyfish: "We are moving from a marine ecosystem dominated by big fish to a soup of small organisms. If we carry on like this the only things in the sea will be jellyfish and plankton soup."
More unintended consequences of our way of life and notions of progress...