Jellyfish have caused a major problem in Oman and marine environmentalists fear that the menace could spread to other parts of the region, including Iran and the UAE.

After disrupting the Ghubra Desalination Plant output recently, the problem seems to have ebbed. However, according to Dr Barry P. Jupp, an Oman-based Marine Ecologist, the danger is lurking and could cause damage anywhere in the Gulf.

"There are millions of jellyfish in the Gulf waters at the moment," Dr Jupp told Gulf News yesterday. Swarms of jellyfish blocked seawater cooling intakes at the Ghubra Desalination Plant and Birka Power and Desalin-ation Plant.

This badly affected water supply to Muscat city in mid-March. In the case of Ghubra Desalination Plant, 300 tonnes of jellyfish had damaged intake screens at GDP causing a 50 per cent reduction in output.

Last year, a large number of jellyfish blocked Oman LNG's seawater cooling system intake. If jellyfish cause a shutdown of Oman LNG, it could cost the company about $7 million a day.

"Therefore, the possibilities of jellyfish causing damage to the national economy is also high," Jupp remarked.

These jellyfish also pose a danger to the offshore oilfields. "Yes, the possibility of offshore oilfields being affected by jellyfish could not be ruled out," the scientist agreed, adding that the jellyfish were reported from Dhofar but have been most common along the Omani coast.

The species causing problems in Oman reaches around 20 cm in diametre with a rigid concave bell, which is dark olive-brown in colour, possibly from commensal algal cells. There are eight pinkish oral arms trailing behind and a fringe of small, brown swimming "frills" on the umbrella margin.

Dr Jupp sad the jellyfish swarming Omani shores are so far unidentified, but resemble a Crambionella. "We are sending samples to the United States to identify the type of jellyfish," he said. He believes this could also turn out to be a new type of jellyfish.

"A behaviourial trait of this jellyfish, of potential great importance in prediction of ingress problems, is that of apparently congregating at the thermocline in stratified water," he pointed out.

The thermocline is a layer between upper, mixed seawater with higher temperatures separated from a lower, cooler layer.

The reason why these jellyfish congregate at, or near, the thermocline might be related to the possible presence of commensal algae.

"If indeed the jellyfish benefits from thephotosynthetic activity of these cells then the maximum photosynthesis is often at or near the thermocline," said Dr Jupp.

He advised taking precautions now as the sea is warming and, once stratification sets in, the thermocline may again be down near the intake with risk of ingress of jellyfish.