The oldest seaweed known to date, dating back to 1,403 years, has been discovered in Finland, providing a new way to determine the age of marine plants.
By measuring the number of genetic mutations over time in underwater meadows that reproduce themselves endlessly, a team of researchers from the universities of London, Davis (California), Kiel and Oldenburg in Germany were able to determine the age of the ancestor of these plants with unprecedented precision.
"It is the first reliable estimate of the age of a clone," Thorsten Ruesch, the researcher who led the study published in June in the scientific journal Nature Ecology and Evolution, told AFP.
Using the "genetic clock" method, the researchers studied 20 populations of eelgrass around the world before discovering, in the Finnish coastal waters of the Baltic Sea, the oldest seaweed bed known to date, more than 1,403 years old.
Determining the age of plants provides insights into how ecosystems work and how aging processes occur in the natural world, according to the researcher.
“It is interesting to understand how plants avoid aging over thousands of years,” said Roesch, a marine ecologist and evolutionary biologist at the GEOMAR Center at the University of Kiel in Germany. “It could provide insights into how humans manage aging.”
He predicted that in the future, the new method could make it possible to discover the oldest aquatic plants, those “100,000 years old or more.”
Eelgrass populations reproduce through flowers, seeds and roots in sediments, provide important marine habitats for other organisms and store carbon dioxide in their stems and roots.
“It is the most important ecosystem in the Baltic Sea,” explained Roesch.
Despite its ability to survive, eelgrass is an endangered species in the Baltic Sea, whose shallow, brackish waters are bordered by Germany, Poland, Finland, Sweden, the Baltic states and Russia.
Nutrient pollution from sectors such as agriculture, combined with rising sea temperatures due to climate change, poses a major threat to eelgrass. "60 percent of eelgrass has become extinct in the western Baltic Sea over the past 100 years," Ruesch noted.
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