Toxic algae rapidly kills coral

By Ella Davies

Harmful algal blooms have the potential to lay waste to coral reefs.

Scientists studying coral reefs in the Gulf of Oman have issued the warning after being shocked by the impact of one large-scale bloom, which destroyed a coral reef in just three weeks.

Around 95% of the hard coral beneath the algae died off and 70% fewer fishes were observed in the area. The rapidly growing patches of microscopic marine plants starve coral of sunlight and oxygen.

Coral reefs are increasingly under threat from environmental stress in the form of climate change, coastal development, overfishing, and pollution.

Climate change is suspected of causing a number of coral bleaching events, as rising sea temperatures stress coral communities. But the latest study, published in the journal Marine Pollution Bulletin, suggests that algal blooms could pose another significant threat. 

Researchers from the United Nations University Institute for Water, Environment and Health undertook studies of coral reef environments at two locations in the Gulf of Oman.

After their initial study, a large-scale algae bloom measuring over 500 square kilometres occurred in the area. When the researchers returned three weeks later they found the coral beneath the bloom had been almost completely destroyed. 

In one area, cauliflower (Pocillopora damicornis) and table top (Acropora arabensis) corals died off completely.

The sudden loss of the reef habitat had a knock on effect for the fish communities living there.

The researchers found an overall reduction of 70%, with 83% of the most abundant species severely reduced or completely eliminated from the survey site near Dibba.

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