Stressed ecosystems trigger jellyfish swarms

Jellyfish occasionally "bloom" in the Mexican Caribbean and the wider basin. Here's a possible explanation from a story posted on Environmental News Service:

ARLINGTON, Virginia, December 16, 2008 (ENS) - Jellyfish blooms are ruining some of the world's most beautiful vacation spots, according to a new online report by the National Science Foundation on massive jellyfish swarms in U.S. waters and around the world.

At least 150 million people around the world are exposed to jellyfish every year, the report says. Swarms of stinging jellyfish and jellyfish-like animals are transforming many world-class fisheries and tourist destinations into "jellytoriums" that are intermittently jammed with the pulsating, gelatinous creatures.

This is happening in U.S. waters from Hawaii to the Chesapeake Bay, where 500,000 people are stung by jellyfish every year.

Another 200,000 people are stung every year in Florida, and 10,000 are stung in Australia by the deadly Portuguese man-of-war, according to the report.

These jellyfish explosions are generated by human activities, some scientists believe. Possible causes include pollution, climate change, introductions of non-native species, overfishing and the presence of artificial structures, such as oil and gas rigs.

Jellyfish swarms have damaged fisheries, fish farms, seabed mining operations, desalination plants and large ships, and they have disabled nuclear power plants by clogging intake pipes.

In the Gulf of Mexico's densest jellyfish swarms there are more jellyfish than there is water - 100 jellyfish can occupy each cubic meter of water.

"I'm often asked whether a single, overarching condition is triggering jellyfish swarms in diverse locations," says Monty Graham of Alabama's Dauphin Island Sea Lab on a barrier island in the Gulf of Mexico. Graham says the abnormally large, dense or frequent jellyfish swarms are "a symptom of an ecosystem that has been tipped off balance by environmental stresses."