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National Science Foundation
Special Report
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Jellyfish Gone Wild — Home
Introduction
Biology
Ecology
Swarms
Sea Stings Back
Bloomin' Magic
Chart - Environmental Stress
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Jellyfish Gone Wild — Text-only | Flash Special Report
Swarms

WHERE SOME REAL SLIMEBALLS GATHER

WHY SWARMS FORM
A swarm is a dense, rapidly-formed cluster of animals. Jellyfish swarms are a naturally occurring, world-wide phenomenon. Scientists believe that jellyfish swarms--even huge ones--have occurred for millions of years and would continue to occur in some locations even without environmental damage from people.

For example, scientists have observed dense summer swarms of sea salps--a three-inch long, tube-shaped gelatinous creature--covering up to 38,600 square miles in the North Atlantic. Such swarms are believed to be natural occurrences that are not influenced by human activities.

Scientists believe that gelatinous creatures swarm when ecological conditions align to favor their survival. These conditions include the concentration of predators and competitors, food availability, currents as well as the temperature, salinity, and oxygen content of the water.

DAMAGE FROM LARGE SWARMS
Natural and unnatural swarms cause various types of problems by:

· Discouraging tourism: Summer blooms of stinging jellyfish keep bathers out of the water in prime tourist destinations from Maryland to the Mediterranean. Various species of box jellyfish, which are among the world’s most toxic creatures, regularly swarm in tropical waters around the world, including Hawaii and Australia.

· Damaging fishing operations: Jellyfish have interfered with fishing operations in world-class fisheries, including the Gulf of Mexico, the Black Sea and the Bering Sea by: 1) busting fishing nets; 2) poisoning and crushing captured fish; 3) consuming fish eggs and young fish; and 4) clogging the engines of fishing boats.

· Crippling industrial operations: Jellyfish have recently disrupted the operations of marine diamond mining facilities in Namibia, desalination plants in Iran and various large ships around the world by clogging intake pipes carrying sea water.

Jellyfish swarms have also forced a number of nuclear power plants around the world to interrupt output or temporarily shut down. In fact, enough jellyfish to fill 50 trucks clogged the intake pipes of a power plant in the Philippines in 1999, and thereby plunged 40 million people into darkness and started rumors of a coup d’etat. (Such freak events prove that jellyfish can be political animals.)

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Caption/Credit:

STRENGTH IN NUMBERS
Because jellyfish reproduce quickly, are hardy and face few competitors or predators in many degraded waters, they can quickly overrun and dominate ecosystems. Credit: Dr. Jamie Seymour, James Cook University

A HEART-BREAKING HAUL
Jamming boat engines, breaking nets with their weight, poisoning and crushing caught fish, jellyfish blooms intermittently shut down the Gulf of Mexico’s $60 million-per-year shrimp industry. Credit: Dauphin Island Sea Lab