An international team with researchers from the University of the Algarve have announced the discovery of the world’s oldest living organism, a seagrass in the Mediterranean that is at least 100,000 years old.
The discovery published this month in the Public Library of Science One journal refers to research carried out between 2005 and 2009 on the marine plant Posidónia oceânica.
“We discovered specimens of Posidónica oceânica that could be between 10,000 and 100,000 years old and possibly more. Never before has such a living organism of this age been found on earth,” said Ester Serrão from the Sea Sciences Centre of the University of the Algarve, who led the Portuguese science team.
The aim of the project was to measure the area covered by a single individual of that species, in order to calculate its age, based on the knowledge that it’s annual growth rate is four centimetres per year.
“The species has been known for a long time, but what we have now discovered is where one individual starts and ends,” said Ester Serrão, adding that “when we see a marine prairie, we don’t know straight away if it came from one seed or several.”
As such, the project aimed to determine whether one segment in an area of the Mediterranean was the same as another segment from a different area. The investigation included studying the genetic characteristics of the sampled segments in a laboratory.
“Through the genetic characteristics, we were able to see that plants in a certain area were all from the same seed and therefore the same individual, that continues to reproduce, creating clones of itself,” she said.
According to the scientist, in cases of cloning, the same specimen of Posidónia oceânica “can occupy hundreds of metres or even kilometres, without a new individual being created as it’s always the same one reproducing itself.”
Based on genetic identification methods, the international team of researchers discovered one individual that occupied seven kilometres and another 15km in length.
The researcher from the University of the Algarve considers however that some of the most extreme cases are not necessarily the result of cloning but also pieces of the seagrass that have fallen away and been transported by the currents to other locations with sediments and kept on growing. With this in mind, the 15km long specimen has been dated to around 100,000 years old, instead of 200,000 years old.
Even so, there are other individuals dated to tens of thousands of years from 1,544 samples collected at 40 different marine prairies along 3,500 kilometres of the Mediterranean sea.
Ester Serrão laments however that despite the species’ resistance and longevity, it could be dying out at a rate of 10 percent in the last 100 years. This is thought to be mostly due to maritime pollution that clouds the waters, making it difficult for photosynthesis to occur.
The field work for this study was carried out between 2005 and 2008, after which laboratory investigation was carried out in 2009 at the Sea Sciences Centre of the University of the Algarve.