"Freshwater jellyfish are about the size of a quarter. The best time to see them is in mid to late summer floating or swimming at the water's edge. Sightings occur in a somewhat yo-yo cycle. Numerous sightings one year will be followed by no sightings at a site for a year or more. This is one of the mysteries associated with the organism."Jellyfish are the adult stage of their life, much like the caterpillar-butterfly life cycle. After spending most of their life as polyps attached to the bottom structures of quiet water, they split off a bud which drifts off as a jellyfish, reproducing by releasing eggs or sperm which fertilize and settle on the bottom to start the cycle again.
Jellyfish eat zooplankton, worms and other small creatures.
"Once prey come in contact with the tentacles, venom is injected from the tentacles and the paralyzed organism is brought into the jellyfish's mouth and digested. The stings these tiny tentacles inject pose no threat to humans."Once again, the biodiversity of the Ozarks amazes me. Intended or unintended, we seem to have it all. I am waiting for the first report of a polar bear any day now.
Jellyfish Gone Wild
Smithsonian has a big article on jellyfish titled The New King of the Sea. It highlights the rapidly exploding jellyfish populations in recent years. Not only are numbers of jellyfish expanding exponentially, but the previous seasonal patterns are disappearing as masses of jellies are showing up any time of the year. The shear bulk of these swarms has had a significant impact on human and marine activities as described below.
"Nightmarish accounts of “Jellyfish Gone Wild," as a 2008 National Science Foundation (NSF) report called the phenomenon, stretch from the fjords of Norway to the resorts of Thailand. By clogging cooling equipment, jellies have shut down nuclear power plants in several countries; they partially disabled the aircraft carrier USS Ronald Reagan four years ago. In 2005, jellies struck the Philippines again, this time incapacitating 127 police officers who had waded chest-deep in seawater during a counterterrorism exercise, apparently oblivious to the more imminent threat. (Dozens were hospitalized.) This past fall, a ten-ton fishing trawler off the coast of Japan capsized and sank while hauling in a netful of 450-pound Nomura’s jellies."The NSF 2008 report, Jellyfish Gone Wild mentioned above lists many interesting jellyfish facts as well as the more dramatic incidents.
- Twenty to forty people die in the Philippines each year from box jellyfish stings that can kill within three minutes.
- Chesapeake Bay reports over 500,000 jellyfish stings each year.
- One third of the weight of all life in Monterrey Bay is made up of jellyfish.
- 400 vast Dead Zones in world oceans are too polluted for almost all life except jellyfish.
- 500 million refrigerator-sized jellyfish float into the Sea of Japan daily during blooms.
"During the 1990s, a voracious, invasive jellyfish-like creature known as the comb jelly was introduced into the Black, Azov and Caspian Seas. Uncontrolled by natural predators, comb jelly populations quickly ran wild. The rise of the comb jelly contributed to crashes in the populations of anchovies in the Black and Azov seas and to crashes of a small commercial fish known as kilka in the Caspian Sea.
How did the comb jelly damage the populations of these commercial fish? By eating their eggs and larvae and by eating the same zooplankton prey they eat. "As usual, the role of human activities in the dramatic increase of jellyfish population is unknown. Whether "global warming," acidification of the seas due to carbon dioxide or pollution are major factors is unknown. But in the words of the NSF report, "The global influence of jellyfish on marine ecology warns all of us: Ask not for whom the jellyfish’s bell tolls; it tolls for thee."
The Ozarks Water Watch contains information on their presence in our local lakes.
The NSF report Jellyfish Gone Wild is full of information on the life cycle of jellyfish as well as their swarming locations and impacts.