And once more, we get to thank the globe-trekking Jackie Chambers for today’s photograph and write-up! Jackie writes:
I came across this fantastic ‘fiber ball’ on the beach while doing field work in southeastern Spain. The balls, or aegagropiles, are actually composed of the fibrous remains of Posidonia oceanica. Over time, dead fibrous tissue of individuals of this species are tossed about by waves. The constant rolling action of the sea eventually forms this material into balls which wash up on the beach.
Sea grass, or Neptune grass, is a flowering plant adapted to live underwater. It is native to the Mediterranean Sea where it forms large undersea meadows (see meadow photograph on this page). It has strap-like leaves which can be 1cm wide, and can reach up to 1m long. The species produces green flowers, and the fruit is sometimes called the “Olive of the Sea” (photograph via Forum Natura Mediterraneo). Like many true aquatics, it is the movement of the water that ensures the pollination and seed dispersal of this interesting plant.
For photos of the plant structure, clearly showing the live green leaves, the fibrous remains of old leaf sheaths, the rhizomatous root, an aegagropile, as well as flowers and fruits, see this detailed article (in French).
Posidonia oceanica is ecologically important as it provides habitat for a wealth of underwater creatures and plays a key role in the health of underwater ecosystems. Neptune grass is often called the “Lungs of the Mediterranean Sea”. Habitat destruction and pollution are threatening these populations.