Toxic algae rapidly kills coral

revhtree · Oct 8, 2010

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.

Dead coral (Pocillopora) under algae
The toxic algae starves coral of light 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.
Coral reef, Gulf of Oman
The reef was rich in life before the algal bloom

Gulf parrotfish (Scarus persicus), pearly goatfish (Parupeneus margaritatus) and blackspot snapper (Lutjanus ehrenbergii) were among the affected species.

Analysis showed that hard corals were particularly vulnerable to the presence of the algae Cochlodinium polykrikoides.

"We were surprised at the extent and speed at which changes to the coral reef communities were affected," says marine ecologist Andrew Bauman.

In recent times, the increased occurrence of rapidly growing areas or 'blooms' of algae have been attributed to human activities.

Eutrophication, excess nutrients in coastal areas caused by run-off from agricultural fertilisers and human sewage, is often cited as the trigger for these phenomena.

Read More: BBC - Earth News - Toxic algae rapidly kills coral

jcom · Oct 8, 2010

The only way to slow this from happening (and I mean "slow" and not "prevent") is to create more and more marine/reef sanctuaries much like has been done on land with preserves, national parks, etc. Unfortunately, with reefs systems, there's no way to prevent the phosphates and other contaminates from entering these areas through tidal currents, weather patterns, etc. The increasing threat of polution on this planet will, I believe, unfortunately decimate our world's reef systems well before we see the more extreme effects above the surface. Actually, it's already the case. The oceans, while massive in size, can only be so resilient against nearly 7 billion people, most of whom don't really care.

Sad but true.