San Francisco swimmers feel sting as jellyfish thrive

San Francisco Chronicle: Schools of creepy brownish jellyfish known for their painful stings are lurking in San Francisco Bay waving their long, poisonous tentacles like they own the place. One touch from a nettle's long, brown tentacles will result in a powerful, numbing jolt that can hurt for hours and sometimes days.

The gelatinous creatures are relatively common in the ocean along the West Coast, but nobody can remember so many of them floating in bay waters at one time. The critters, known scientifically as Chrysaora fuscescens, are darker and bigger than the Moon or Bell jellies, which are frequently seen in the area.

…Marine biologists believe strong coastal upwellings of nutrient-rich water and northwest winds are responsible for the influx of nettles, which usually reside over vast stretches of the Pacific and Indian oceans. The stinging jellies, which can be found floating on the surface or hundreds of feet under the water, are more commonly seen near shore during the fall and winter.

Vast blooms of sea nettles have been known in the past to congregate in one location, sometimes for months at a time, clogging fishing nets and depleting the water of plankton.

Biologists around the world are concerned about an apparent increase in the number and size of jellyfish blooms of all species. Studies are being conducted to determine whether the prevalence of jellyfish, which reproduce both sexually and asexually, has anything to do with global warming. "This bloom in the bay may or may not be related to climate change, but it's definitely something to be concerned about," Grassmann said....

Pacific sea nettle, shot by Ed Bierman from Redwood City, USA, Wikimedia Commons via Flickr, under Creative Commons Attribution 2.0 License