Polluted Water Caused Coral Death in Great Barrier Reef

First Posted: Nov 13, 2012 12:54 AM EST

A new study suggests that a large number of Europeans settling in Australia caused a massive coral collapse at the Great Barrier Reef nearly five decades ago.

The study published in the Proceedings of the Royal Society, Biological Sciences, found that water from farms corrupted the ocean waters off Queensland coast and replaced the clear natural branching of coral species with corals that were scrawny in size. It is also found that the damage had been caused by humans had been done much before the promotion of reef tourism and climate change.

"There was a very significant shift in the coral community composition that was associated with the colonization of Queensland," said study co-author John Pandolfi, a marine biologist at the University of Queensland, Australia, according to Live Science.

European settlers began invading Queensland in the 1860's, cut down forests for sugar plantations and grazing of domesticated sheep. By the early 1900's fertilizers and pesticides from the farmlands and factories drained into the rivers and nearby ocean.

The disappearance of nearly half of the Great Barrier Reef in the last 30 years has raised many questions in the minds of the researchers. Snorkeling and climatic change were the obvious reasons earlier studies had targeted.

But Pandolfi and his team doubt these reasons and boldly say that the Great Barrier Reef began to die much earlier than thought. As a part of their experiment, Pandolfi and the team dug out the sediment cores from a depth of 6.5 feet to16.5 feet from the seafloor at Pelorus Island. Pelorus Island is surrounded with coral reefs off the coast of Queensland.

Corals have a mechanism that is rather fascinating. When a coral dies, another coral sprouts out on the dead skeleton and ocean matter buries it consequently. By dating different layers of that sediment they had extracted, the marine biologists reconstructed the story of the reef, the Live Science report said.

Acropora coral dominated the reef for a millennium. This massive, three-dimensional coral can grow to 16 feet (5 m) high and span 65 feet (20 m) across, forming a labyrinth of nooks and crannies for marine life to hide in, Pandolfi said. "They're like the big buildings in the city, they house a lot of the biodiversity. ''

Somewhere between 1920 and 1955, the fast growing Acropora stopped growing altogether and long and lean Pavona coral took its place. Pavona coral is said to be a slow grower. This spelled trouble for the array of animal species which took shelter in the reef.

The Acropora c oral provides resistance from waves to these animal species and the slow growing Pavona could not be of much help to these species in providing shelter. Pandolfi's team believes that the corrupted waters from the farmlands poisoned the native species of corals and this water also caused the algae to thrive and gagged the native coral species when they tried to grow back.

Pandolfi and his team believe that humans have been damaging the coral reefs far longer than previously thought and the only solution to this problem is to stop or reduce the polluted water from entering the ocean floor.

"Acropora coral weren't able to come back after the 1950's. Any kind of measures that are going to improve the water quality should help those reefs to recover," Pandolfi said.

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