'Trojan horse' effect may explain jellyfish blooms

Sep 07, 2012
'Trojan horse' effect may explain jellyfish blooms

(Phys.org)—Man-made structures such as harbours, tourist facilities, oil rigs and aquaculture farms provide ideal sanctuaries for jellyfish polyps to flourish and may explain an apparent increase in jellyfish blooms in many coastal waters around the world.

That's the conclusion of a new study published by a group of international researchers, including lead author Winthrop Professor Carlos Duarte, Director of the Oceans Institute at The University of Western Australia.

Their paper Is sprawl a cause of blooms? appeared this week in the journal Frontiers in Ecology and the Environment.

Professor Duarte said most theories that seek to explain increased jellyfish blooms focus on jellyfish at their more mature swimming stage and factors such as a lack of predators or competitors due to overfishing.

But the new study examined the tiny polyp phase of jellyfish and found they congregate in millions on the underside of man-made structures.

"We call this new proposition the '' hypothesis," Professor Duarte said.

"The proliferation of such as harbours, shipping facilities and aquaculture structures provides a habitat for jellyfish polyps and may be an important driver in explaining the global increase in jellyfish blooms."

Professor Duarte said jellyfish larvae typically settle on a hard surface and grow into polyps as part of a colony.  The polyps are generally inconspicuous because they are very small - usually only a millimetre or so in length.

The study examined polyps growing on a variety of man-made structures around the world - including in Japan, Britain, Spain and Slovenia - and looked under docks, piers, pontoons and , and on the underside of oysters attached to piers.

"Jellyfish existed on the underside of such artificial structures at densities of more than 10,000 individuals per square metre, and sometimes up to 100,000 per square metre," Professor Duarte said.

Research was also conducted in Chesapeake Bay in the US and in a laboratory with a Mediterranean jellyfish species to examine how larvae settled on oyster shells, flagstones and 16 other surfaces, including bricks, ropes, cans, wood, concrete and plastic.

Explore further: Europeans have unknowingly contributed to the spread of invasive plant species in the US

Related Stories

Dutch zoo breeds own jellyfish

Sep 29, 2007

Marine biologists at a Dutch zoo say they have succeeded in the difficult task of breeding jellyfish in captivity.

Jellyfish on the rise: study

Apr 18, 2012

Jellyfish are increasing in the majority of the world's coastal ecosystems, according to the first global study of jellyfish abundance by University of British Columbia researchers.

Spanish resort in jellyfish alert

May 27, 2011

Authorities in the Spanish tourist hotspot of Benidorm said Friday they have reopened its beaches to tourists after removing more than a tonne of dangerous jellyfish.

Jellyfish joyride a threat to the oceans

Jun 08, 2009

Early action could be crucial to addressing the problem of major increases in jellyfish numbers, which appears to be the result of human activities.

Recommended for you

Restored streams take 25 years or longer to recover

6 hours ago

New research has found that the number of plant species growing just next to restored streams can take up to 25 years to increase above those channelized during the timber floating era. This is according ...

Why haven't Madagascar's famed lemurs been saved yet?

9 hours ago

Lemurs are cute – there is no denying it. Their big eyes and fluffy faces mean they really are the poster animals of Madagascar, an island known internationally for its unique flora and fauna. But the plight ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.