oceans became rich in oxygen as we know now about 600 million years ago, during the last phase of the Ediacaran Period. Now a team of biogeochemical has found evidence that the oceans were re-anoxic (oxygen-poor) some 499 million years ago, shortly after the appearance of animals on Earth. And it remained so for a period of between 2 and 4 million years . Researchers at the University of California, Riverside, suggest that such anoxic conditions could exist even for a much wider range of time.
Timothy Lyons's team argues that such fluctuations in oxygen levels of the oceans are the most likely cause of the explosive diversification life forms that marked the Cambrian period, made between 540 and 488 million years.
The transition from a sea usually rich in oxygen during the Cambrian, until fully oxygenated sea that we have today was not as simple as has been widely accepted until now. New research shows that the ocean had fluctuations between different degrees of oxygenation. Such fluctuations played an important, perhaps primary in shaping the early evolution of animals on the planet, to promote certain extinctions and clearing the stage for the new bodies take their place. Researchers now
working to find an explanation for this lack of oxygen in the oceans 499 million years ago.
may seem of little interest to society to investigate the causes of a phenomenon so long ago, but the truth is that investigations are made could be useful now and in the near future. Currently, some parts of the world's oceans are becoming poor in oxygen. Chesapeake Bay (surrounded by Maryland and Virginia) and the "Dead Zone" in the Gulf of Mexico are two examples.
"We know that the Earth had similar situations in the past. Knowing the causes and consequences can provide clues essential to what the future has in store for our oceans, "says Benjamin Gill, the research team.
Carla Gallo
0 comments:
Post a Comment