07 February 2012


Posidonia oceanica. Via.

 A new paper in PLoS ONE reports that a patch of Mediterranean seagrass of the species Posidonia oceanica is the oldest known living organism on Earth.

The researchers sequenced the DNA of seagrasses from 40 underwater sites between Spain and Cyprus, covering 3,500 kilometers/2,175 miles of seafloor.

Map via Wikimedia Commons.
They found one genetically identical 15-km/9-mile-long meadow off the island of Formentera in the Balearic Islands.

Seagrasses reproduce by cloning and individuals can reach great size and age.

Based on the annual growth rate of P. oceanica, the researchers calculated the Formentera meadow's age as between 80,000 and 200,000 years old.

Clearly P. oceanica are good adaptors. Yet the next few decades may prove more taxing to than anything encountered in the past 200,000 years. From the paper:

The finding of P. oceanica clones.. that are extreme in size (km-sized) and age (multi-millenary old) across the Mediterranean indicates that some meadows are the result of ecological and evolutionary processes integrated over long time scales. Time scales such as these are in a stark contrast to the current rapid and acute impact caused directly or indirectly by human pressure on this species... [E]ven though such phenotypic plasticity possibly evolved across millennia, it may well be challenged by the unprecedented rate of environmental change imposed by current global climate change, including temperature increase and ocean acidification, and recent anthropogenic pressure on coastal areas resulting in changes in water quality, eutrophication, and nutrient load, particularly in seagrass meadows.

The paper:

  • Arnaud-Haond S, Duarte CM, Diaz-Almela E, Marbà N, Sintes T, et al. 2012 Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica. PLoS ONE. DOI:10.1371/journal.pone.0030454
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