Toxic algae 'wiped out dinosaurs'

Previous studies had claimed an asteroid impact produced devastating climate changes and rising sea levels which caused the mass extinctions over the earth's 4.5 billion year existence.

But a team of American geologists and toxicologists claim algae commonly found naturally around the world could be the culprit that led to the demise of the dinosaurs.

They say the current environmental conditions show significant similarities to times when previous mass extinctions occurred and warned that levels of toxic algae are increasing.

During the summer scientists warned of toxic in algae blooms in lakes and ponds in the North West and West Midlands.

Current thinking blames either climate changes, sea level, volcanic activity, or asteroids as primary causes for deaths of more than 50 percent of life on Earth.

However geologist James Castle and ecotoxicologist John Rodgers of Clemson University said they all contributed - but killer algae was the final straw.

The researchers spent two years analyzing data from ancient algal deposits — stromatolite structures.

They found evidence that blue-green algae, which produce poisons and deplete oxygen, were present in sufficient quantities to kill off untold numbers of plants and animals living on land or in the sea.

Their research presented to the Geological Society of America goes against the perceived theories of what caused five major extinctions and a number of minor die-offs during the 545-plus million years.

During this period life with "hard parts" — skeletons and shells — has flourished and left fossils known by the Greek Phanerozoic for "visible life."

Studying fossil remains, they claimed asteroid-caused extinction was not proven.

Mr Castle said: "The fossil record indicates that mass extinctions ... occurred in response to environmental changes at the end of the Cretaceous period.

"However, these extinctions occurred more gradually than expected if caused solely by a catastrophic event.

"This hypothesis gives us cause for concern and underscores the importance of careful and strategic monitoring as we move into an era of global climate change."

They warn the level of "modern toxin-producing algae is presently increasing, and their geographic distribution is expanding...."

Mr Rodgers added: "Scientists from around the world have been sending us data that support our hypothesis and our concern about the future.

"I look forward to the debate this work will generate. I hope it helps focus attention on climate change and the consequences we may face."

Outbreaks of blue green algal blooms are common in lakes and waterways around the world with four-mile long Bala Lake - which is known as Llyn Tegid in Welsh - in Gwynedd, being the latest affected region.

It produces toxins when it blooms causing humans or animals who come into contact with it to develop rashes or become ill if they drink it.

But it can kill fish due to lack of oxygen in the water, and toxins can kill fish, animals and birds.

The scientists' theory "Hypothesis for the role of toxin-producing algae in Phanerozoic mass extinctions based on evidence from the geologic record and modern environment" was published in journal Environmental Geosciences.