Mass extinction has shuffled Ocean's basic ecology- Study

The mass extinction of the Earth’s land and sea creatures that occurred some 250 million years ago not only wiped out an estimated 95% of marine species and 70% of land species, but has also changed the basic ecology of the world's oceans, a new research carried out by the Australian and US researchers revealed.

Peter J Wagner, associate curator of fossil invertebrates at the Field Museum in Chicago along with his fellow experts from James Cook University in Townsville, Queensland, examined the new Paleobiology Database, a repository of fossil occurrence data, to reach at a broad objective assessment of changes in the complexity of marine ecology.

Although the researchers are still ambiguous about causes behind the largest extinction, called the ‘Great Dying’ occurred at the end of the Permian Era, but in their new study they said one of the cause was oceans’ dominancy which shifted from ocean’s ecologically simple communities to a complex one.

“We think these are the first analyses of this type at this large scale,” said Wagner, who worked with Matthew Kosnik of James Cook University. “They show that the end-Permian mass extinction permanently altered not just taxonomic diversity but also the prevailing marine ecosystem structure.”

The research published in journal Science on November 24, 2006 unveiled that before extinction, the seas were home to a balance of both ecologically simple communities and complex ones, but after the phenomenon, complex communities displaced simple ones. In that shuffle the complex ones outnumbered their counterpart nearly 3:1, a ratio that still prevails.

That shuffle gives evidence of the current dominance of, higher-metabolism, mobile organisms, like snails and crabs that go out and find their own food, and the decreased diversity of low-metabolism, stationary organisms such as lamp shells and sea lilies, which filter nutrients from the water.

The species that did not move or search for food were largely wiped out, they concluded, while more complex life forms that went in search for food seized the ocean.

"It's a simple system when everyone comes in and they grab their portion of the pie, and the pie doesn't change," said Wagner. "The other is a more complicated system, where organisms come in and they take a piece of the pie, but then they put something back into the pie for other organisms to take"

The ecologists have also threatened that current changes stimulated by humans to the ecosystem could have a similar impact.

Calling their study as a wake-up call for the world, Wagner says, "Studies by modern marine ecologists suggest that humans are reducing certain marine ecosystems to something reminiscent of 550 million years ago, prior to the explosion of animal diversity. The asteroid that wiped out the dinosaurs couldn't manage that."