Jellyfish increase points to declining ocean health

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Increasing numbers of jellyfish across the world may be linked to the declining health of the oceans, scientists report.

In the past year, jellyfish swarms on Cte d Azur in France, the Great Barrier Reef in Australia, and Waikiki in Honolulu, USA, have led to the closure of beaches " causing issues for tourists as well as fishermen.

However, the problem on the beach is a social problem, Dr Josep-Mara Gili told the New York Times. The big problem is not on the beach " it s what s happening in the seas.

It is believed that a combination of overfishing, pollution and rising sea temperatures have led to the explosion of jellyfish populations.

A report being prepared by the National Science Foundation in the USA is set to highlight the main problem areas, and attempt to link in trends such as climate change, where jellyfish numbers have risen.

The areas listed include Britain, Mexico, Hawaii, Japan, Namibia and Australia " where in 2007, 30,000 people were treated for jellyfish stings; double the number recorded in 2005.

These jellyfish near shore are a message the sea is sending us saying, ~Look how badly you are treating me, said Dr Gili.

The overfishing of natural predators, including Tuna and Swordfish, has led to reduced control over jellyfish numbers, while reduced competition from small fish for plankton has contributed to creating an environment in which the jellyfish can thrive.

Rising sea temperatures have also meant that jellyfish populations are able to extend beyond their natural ranges, and inhabit new waters.

Jellyfish can range from being relatively harmless, such as the Moon jellyfish, Aurelia aurita, to deadly, including the Giant box jellyfish, Chironex fleckeri. Stings from the Mauve stinger jellyfish, Pelagia noctiluca, common in the Mediterranean, can last from weeks to years.