The many faces of the red tide

Scientists worldwide are working to unravel the man-made and natural factors that create toxic algal bloom.

An aerial image showing the advance of the algal bloom on the coast of Dubai.

Scientists worldwide are working to unravel the complex interplay between the many man-made and natural factors that combine to create the ideal conditions in which the toxic algal bloom, now massing off the west coast, can spread, reports Vesela Todorova In Texas, the marine biologists call it Aureoumbra lagunensis - a tiny aquatic plant, only two millionths of a metre in diameter, which first appeared in 1990, infesting the Laguna Madre coastal lagoon in great, dense brown patches and dominating the southern Texas waterway for 17 years.

In New York's Great South Bay, it is known as Aureococcus anophagefferensm and it devastated Long Island's vibrant scallop industry within three years of appearing in the summer of 1985. Thousands of kilometres away in Bulgaria, they have as many as 20 different scientific names for the various species that from the early 1970s and throughout the 1990s devastated the northwestern Black Sea. Everywhere, it goes under a generic name - depending on the colour of the organisms involved, sometimes it is the brown tide, sometimes the green or red tide - but wherever it appears this tiny plant, a denizen of the lowest levels of the marine food chain, is feared.

Although the names differ, depending on which specific species of microscopic plant is involved, the basic mechanism of these phytoplankton, which thrive in oceans, rivers or lakes alike, is the same. Under certain favourable conditions, they can multiply so rapidly they form dense patches known as an algal bloom. According to UNESCO, about 300 species of algae are capable of blooming; of these, almost a quarter are known to produce toxins.

Important sources of food for marine creatures, phytoplankton can also turn nasty, becoming dangerous to people and causing havoc to entire eco-systems, wiping out fish, sea birds, coral and seagrass. This is the condition of the phytoplankton now massing off the west coast - seen yesterday in great swathes some 30 metres off Jumeirah Beach, stretching from the dry docks near the Creek to the Burj al Arab Hotel.

Under normal conditions, the phytoplankton are present in only small numbers, easily kept under control by diners from across the food chain, from other organisms up to fish. Last August, however, dense patches of brownish-red water were spotted in UAE water, off Dibba and Fujairah on the country's Indian Ocean coast. The bloom has persisted for months, killing off hundreds of tonnes of fish and causing coral die-offs.

Last week, a large patch of reddish water was seen off Dubai and early this week some of the bloom made landfall, prompting Dubai Municipality to close two popular beaches for fear it could be harmful to humans. Quite why such blooms are taking place is still not fully understood and scientists worldwide are still working to unravel the complex interplay between the many man-made and natural factors that combine to create the right - or wrong - conditions.

One thing that is clear, however, is that harmful algal blooms have multiplied in recent years - and there is a growing belief among many biologists that the urbanisation of coastlines may be playing a major role. "Harmful blooms are having more impact, in my view because human exploitation of the coastal zone is having more impact," says Tim Wyatt, who compiles a newsletter on behalf of the Harmful Algal Bloom Programme of UNESCO's Intergovernmental Oceanographic Commission (IOC).

Until recently, it was thought that the increase in nutrients in the sea from sewage treatment plants, agriculture and other sources was the main factor behind the boom in algal blooms, he says, but now a more complex picture is emerging. Activities such as fishing are also thought to have an impact, as do other changes in the ecosystem. For example, says Mr Wyatt, the supposed increase in bloom frequency in Chesapeake Bay in the US may be related to the near-extinction of oysters there.

Researchers are also investigating how changes in the global climate fuelled by the excessive burning of fossil fuels could be affecting phytoplankton. Last October, studies carried by the Environment Agency-Abu Dhabi (EAD) identified several micro-organisms which were present in large numbers in the waters off the east coast. The dominant strain was Gymnodinium catenatum, a phytoplankton that is toxic to people if eaten in seafood. Depending on the species, the toxins may also become airborne in sea spray. Effects can range from minor gastrointestinal problems to neurological disorders, including loss of memory, and even death, but the extent of the problem globally is not known.

"There is," says the IOC, "currently no international record of the number of incidents of human intoxication caused by contaminated seafood. The numbers appearing in presentations at international meetings are undoubtedly underestimates, as many cases and even fatalities can be assumed to pass undiagnosed and hence unreported in the official reports." To the relief of the EAD and the authorities, tests carried out later in 2008 and early this year showed that the balance had shifted, with another species, Cochlodinium polykrikoides, now dominating. Cochlodinium, which is also responsible for the current Dubai bloom, is not known to be poisonous to people.

However, people living near the water should still take certain precautions, says Dr Thabit Zahran al Abdessalaam, director of marine biodiversity management at EAD. While the micro-organism has not been known to be poisonous in the past, a bloom has never been seen in UAE waters before and some species, he says, have changed their toxicity depending on their location. But while the impact of Cochlodinium polykrikoides on people is still being established, there is no doubt about the effect it has on marine life, damaging fish gills and causing them to suffocate.

The sheer volume of algae in UAE waters - excessive concentrations of up to 27 million individuals per litre were detected in some of the worst affected areas on the east coast last year - is creating its own problems. As the micro-organisms die, they sink to the bottom of the ocean, where they rot, a process that consumes large amounts of oxygen. The foul smell reported by residents of Dibba and Fujairah is not caused by the living bloom itself, but is a result of the stagnant, oxygen-depleted water caused by its decomposition.

This same lack of oxygen makes it harder for all kinds of marine life to survive. So far, Dubai has been spared the large numbers of fish deaths and disruption to tourism that have affected Fujairah for more than six months. Nevertheless, the presence of the blooms calls for a rethink of the way people use the coastline, says Dr al Abdessalaam. Human activities such as shipping and tourism, as well as the development of large areas of coastline, all interrelate, creating potentially favourable conditions.

"Previously most management aspects were limited to mitigation of the blooms," he says. "But we need to go back and look at land use strategies and other aspects. We have to go back to proper designing and planning." It is thought that the two main species of algae that have been found blooming in UAE waters were brought to the east coast by ships that discharged ballast water taken on board in other locations. Gymnodinium catenatum, the toxic micro-organism which can paralyse people who eat infected shellfish, usually lives in cooler waters in more temperate regions and the change in environment may have been responsible for its excessive blooming.

Cochlodinium polykrikoides was recorded in Gulf waters for the first time in 2006, by scientists from the Kuwait-based Regional Organisation for the Protection of the Marine Environment. Once both these species were introduced, they needed only favourable conditions to allow them to multiply rapidly. "The two most important factors are the presence of nutrients and the hydrology of the area," says Dr al Abdessalaam.

Nutrients such as phosphorus and nitrates can find their way into the oceans by various routes. The two most important channels are effluent from sewage treatment plants and the wind, which carries particles into the sea. Rains can also wash nutrients off the land from fertilisers used in gardens and agriculture. One way to control the amount of nutrients is to time the discharge from treatment plants so that the chances of overload are reduced, says Dr al Abdessalaam. Another way is to maintain natural "barrier" areas, which act as filters.

"The best way is to try and retain some natural vegetation and habitats such as mangroves and mudflats in the coastal area." The natural profile of a body of water can be seriously affected by man-made interventions; for example, introducing new breakwaters, creating confined areas and slowing down water circulation, creates favourable conditions for blooms. "Stagnation increases the chances of nutrients accumulating," says Dr al Abdessalaam; it also aids the formation of patches of algae, since they are prevented from drifting away on currents.

The coast of Dubai and those of Fujairah and Dibba have all been affected by large developments, including many new ports, marinas and leisure or residential projects. The activities that accompany the building of these facilities can also contribute to the problem. Dredging, for example, stirs up sediment that lies on the seabed, increasing the amount of nutrients or propelling certain types of algae up the water column.

The invasion of the blooms has also brought home to decision-makers the lack of trained personnel capable of responding to the situation. Of all seven emirates, only Abu Dhabi has a harmful-bloom monitoring programme. It was set up in 2003, when EAD started sampling along the coast to identify the phytoplankton species off the emirate. In March, the federal Ministry of Environment and Water announced it was creating its own monitoring and response network of laboratories and trained scientists.