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Abu Dhabi, UAETuesday 19 June 2018

Red tide returns to Saadiyat Beach days after it reopened

The beach was shut last week because of the harmful algal bloom 

Red tide washes ashore on Saadiyat public beach. Victor Besa / The National 
Red tide washes ashore on Saadiyat public beach. Victor Besa / The National 

Saadiyat Beach has been closed to swimmers again, days after the sea was declared free of a harmful algal bloom.

The beach was first shut last week due to a red tide, which is caused when a species of algae grow out of control.

It was reopened a couple of days later after tests confirmed that the bloom had cleared. On Sunday the beach was closed again after more red tide was spotted.

A red tide is the name given to a natural phenomenon which occurs when dinoflagellates, a species of algae, blooms.

Dinoflagellates contain pigments that vary in colour from brown to red during the day — giving them their name — but they can appear luminescent at night — as happened in California recently when waves containing a red tide glowed as they broke on the shore off the coast of San Diego.

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There are thousands of species of dinoflagellates — and a few dozen can be extremely toxic to people and marine life.

The species found in the waters surrounding Saadiyat both last week and this week is not toxic, but it can cause skin irritation, so authorities closed the beach as a precaution.

Red tides tend to occur more frequently in warmer waters. And the Arabian Gulf is the hottest sea in the world, making it particularly susceptible to the phenomenon.

Rising temperatures combined with a strong current and dusty winds could be acting like a fertiliser, causing the algae to bloom, say scientists.

“If you have a lot of winds coming off the land it could be enhancing the amount of iron and allowing them to bloom,” John Burt, Associate Professor of Biology at NYU Abu Dhabi told The National last week, when the beach first closed.

“We have had winds for the past week coming off the land, so it is possible that we have this iron deposition going on that is enhancing things, along with the rising temperature. So when the winds turn around and start coming off of the sea again, we will see if it disappears or not. That would be a good indication of whether dust is involved.”

Human activities such as aquaculture and the discharge of water from sewage treatment plants also play a role.

High concentrations of red tide have in the past clogged the filters of desalination plants in the UAE.

And in 2008 and 2009, a red tide caused serious damage to the UAE’s marine life, damaging coral and wiping out large populations of fish in Dibba Rock.

In 2008 and 2009 red tide devastated fish and marine life, which is only now recovering. Matthias Seifert for The National
In 2008 and 2009 red tide devastated fish and marine life, which is only now recovering. Matthias Seifert for The National

According to a study that catalogued the effect of the red tide in Fujairah on fish species 10 years ago, populations of commercial fish in Dibba and nearby East Musandam plummeted. About one-third of blackspot snappers survived, as did about 10 per cent of hammour.

Just over half of the sea floor had been covered with living hard coral, compared with less than three per cent during the bloom, according to the study. Dead coral jumped from eight per cent to about 60 per cent. The effects were similar to those of severe bleaching events, which happen when brightly coloured coral reefs turn white due to pollution or other stresses, the report said.

Shark conservationists said this year that numbers of the apex predator in the bay off Dibba Rock in Fujairah are only now recovering.