Red Algae are unsightly, block seawater intakes and their excretions kill fish and make swimmers’ eyes sting. A scourge in parts of the US and Japan, it’s been around Oman for decades, but came for the first time to the Gulf in March. It’s a warning that the marine environment essential for the eight countries with coastlines on the waterway is in jeopardy.

The Gulf, named the Persian Gulf by some and the Arabian Gulf by others, combines the characteristics of a lake and an ocean. It is connected with the Arabian Sea, but through a strait that is only 50 kilometres wide at its narrowest. Water flows into it from the rivers Tigris and the Euphrates and through waterways on the Iranian coast. But it takes up to 200 years for the water to be entirely replaced.

The Gulf is, as a consequence, one of world’s warmest and most saline seas. Coastal water temperatures can rise to 35 degrees Celsius in the summer. Salinity is more than 50 per cent higher than the average. Shallow, hot and salty, the Gulf nevertheless supported coastal fishermen for centuries and was, until the 1930s, an important source of natural pearls. The waters of the Gulf have been abused with increasing intensity ever since.

The Gulf today is one of world’s most important sea routes. About 12 million barrels of oil are exported daily by ship from the region. This takes at least six huge tankers every day. More than 20 million containers are delivered to Gulf ports every year. This involves more than 2,000 huge container ships - and at least the same number of break-bulk cargo vessels - entering and leaving the seaway annually.

Land-based pollution outstrips the shipping industry’s impact on the Gulf. At least 10 million people live in towns and cities on its Arabian coast. All depend almost exclusively on desalination plants fed by seawater. The brine produced is dumped in the Gulf. At least 10 per cent of the treated sewage effluent that results is pumped there too. The long-term consequences could be profound.

Increasing pollution

On the Iranian side of the Gulf, the population is more modest. Bandar Abbas, with a population of about 400,000 people, is the most populous Iranian Gulf city. Bushehr, the Islamic republic’s largest sea port, probably has no more than 200,000 people. Iran’s incomplete nuclear power project is close by.

The pace of change is quickening. In 2030, there could be 30 million people living in the Gulf’s coastal cities. Red algae off Dubai’s Jumeirah beach are evidence that the marine environment is already struggling to cope and pollution is probably the principal cause. But the immediate challenge is the Gulf’s increasing salinity and temperature, partly the result of massive increases in the volume of desalinated water production.

Algae may ultimately prove to be a minor issue but the consequences of failing to take into account the impact of land-based development on the sea is not. And there is not much point looking after the marine ecology along the coast of a single Gulf state if it’s being ruinously polluted by another.

There are many differences among the nations of the region. Some may be intractable. But co-operating to protect the long-term health of the Gulf’s marine environment is something everyone should be able to agree about.