Drifting across the world’s oceans are a group of unicellular marine microorganisms that are not only a crucial source of food for other marine life — but their fossils, which are found in abundance, provide scientists with an extraordinary record of climatic change and other major events in the history of the earth.

Now, planktonic foraminifera — single-celled shell building members of the marine microplankton community — have given up a secret of their very own.

It had been thought that all modern planktic foraminifers were descended from the few lucky survivors of the meteor impact that wiped out the dinosaurs and 65 to 70 per cent of life on earth 65 million years ago. However, this might not be the case.

Dr. Chris Wade from the Institute of Genetics, said: “Using genetic data we have been able to prove that the planktonic species Streptochilus globigerus and the benthic — sediment living — foraminiferan Bolivina variabilis are one and the same biological species. Moreover, geochemical evidence shows that this species actively grows within the open-ocean surface waters, thus occupying both planktonic and benthic domains. Such ecologically-flexible species are eminently suited to the recolonisation of the extinction-susceptible planktonic domain following mass extinctions events, such as the end-Cretaceous event.”

Their surprising discovery suggests that planktonic foraminifera may have survived the end Cretaceous mass-extinction by abandoning the poisonous oceans for a refuge in the relative safety of the sea-floor. When the oceans returned to normal, the survivors were able to recolonise the ocean surface once more.

Source: http://communications.nottingham.ac.uk/News/Article/Surviving-mass-extin...