The planet's oldest organism
Beneath the clear waters of the Mediterranean, there lives an organism of immense age. The seagrass meadows you can see from the shores of Alcudia Bay belong to the species Posidonia oceanica, and genetic research has revealed its extraordinary lifespan. While sexual reproduction by flowering does occur, Posidonia primarily expands by asexual cloning. Its underground stems, called rhizomes, spread horizontally, creating genetically identical shoots. This process allows a single individual to grow for millennia.
In 2006, scientists discovered a clonal colony of Posidonia oceanica stretching 8 kilometers between the islands of Ibiza and Formentera. Genetic analysis of samples from across the Mediterranean confirmed that some of these clones are between 80,000 and 100,000 years old. This means a single plant has been growing continuously since the Pleistocene epoch, surviving multiple ice ages. This incredible longevity makes Posidonia oceanica a candidate for the oldest known living thing on Earth. The meadows in Alcudia Bay are part of this same ancient lineage, dates back to a time before modern humans inhabited these islands.
An engine of the ecosystem
Posidonia oceanica is not an alga, but a true flowering plant with roots, stems, and leaves that adapted to life underwater. These underwater meadows are a major ecosystem in the Mediterranean. They generate large amounts of oxygen through photosynthesis, often called "the lungs of the Mediterranean". Per unit of area, they can absorb up to 15 times more carbon dioxide annually than a similar patch of the Amazon rainforest. This "blue carbon" is stored in the dense mat of rhizomes and sediment, where it can remain locked away for thousands of years.
The meadows are a habitat, providing shelter, food, and nursery grounds for thousands of species of fish, crustaceans, and other marine life. The dense network of leaves and rhizomes stabilizes the seabed, preventing coastal erosion by dampening the power of waves. The clarity of Mallorca's famous turquoise waters is a direct result of the filtering action of these vast underwater forests.