Giant algae bloom a worry

Photo: The Canadian Press

The Gulf of Oman turns green twice a year, when an algae bloom the size of Mexico spreads across the Arabian Sea all the way to India.

Scientists who study the algae say the microscopic organisms are thriving in new conditions brought about by climate change, and displacing the zooplankton that underpin the local food chain, threatening the entire marine ecosystem.

Khalid al-Hashmi, a marine biologist at the Sultan Qaboos University in Oman, wrinkles his nose as the research vessel nears the bloom. "Sea stench," he says, referring to the algae's ammonia secretions. "It's here, you can smell it."

He signals the boat to stop as it speeds beneath a gigantic rock arch off the coast of Muscat, the capital of Oman, an arid sultanate on the southeastern corner of the Arabian Peninsula. The captain kills the engine and drops anchor into a slick of bright green muck surrounded by crystal-clear blue water.

The swarms of microscopic creatures beneath the surface of the Gulf of Oman were all but invisible 30 years ago — now they form giant, murky shapes that can be seen from satellites.

Across the planet, blooms have wrecked local ecosystems. Algae can paralyze fish, clog their gills, and absorb enough oxygen to suffocate them. Whales, turtles, dolphins and manatees have died, poisoned by algal toxins, in the Atlantic and Pacific. These toxins have infiltrated whole marine food chains and have, in rare cases, killed people, according to the U.N. science agency.

Scientists based at the Lamont-Doherty Earth Observatory at Columbia University trace Oman's blooms to melting ice in the Himalayas. Less ice has raised temperatures in South Asia and strengthened the Indian Ocean's southwest monsoon. As this weather front moves across the Arabian Sea every year, it churned up oxygen-poor water thick with nutrients that have fueled the rise of a 1.2-billion-year old algae called noctiluca scintillans.