Metal pollution triggered world's largest extinction events

London: Metal poisoning caused the malformation observed in fossil remains of marine plankton from the late Silurian (415 million years ago) and may have contributed to their extinction and that of many other species, new research suggests.

Several Palaeozoic mass extinction events during the Ordovician and Silurian periods (ca. 485 to 420 million years ago) shaped the evolution of life on our planet. Although some of these short-lived, periodic events were responsible for eradication of up to 85 percent of marine species, the exact kill-mechanism responsible for these crises remains poorly understood.

An international team led by Thijs Vandenbroucke, researcher at the French CNRS, and Poul Emsbo from US Geological Survey initiated a study to investigate a little known association between 'teratological' or 'malformed' fossil plankton assemblages coincident with the initial stages of these extinction events.

They said that malformed fossil remains of marine plankton from the late Silurian contain highly elevated concentrations of heavy metals, such as iron, lead, and arsenic.