Posidonia oceanica - Life cycle

Posidonia oceanica represents the submerged habitat with the biggest distribution of the marine ecosystems in the coast of the Pitiusas islands. Without a doubt, it is an important species with high ecological value. It forms meadows that cover and structure the sea bed. Over the years, it creates a natural reef. This reef serves as a shelter, food and reproduction site for a high diversity of plants and animals (approximately 400 spp. of plants and 1.000 of animals). Controls the erosion of the coast line at different levels:

• In shallow waters, the reef-barriers have a filtering function that maintains the sedimentary equilibrium of the coastline.
• The dead leaves floating in the water reduce the force of the waves.
• The bed banks located on the beach hold the sand avoiding its loss during storms.

Posidonia oceanica is a superior plant that belongs to the group of flowering plants adapted to marine environment. It has roots, stem, leaves, flowers and fruits like terrestrial plants. Its life cycle generates landscape changes, due to their stages of flowering, fruiting and renewal of leaves. Posidonia oceanica grows mainly on soft bottoms between the break zone and 40 m depth approximately. It is the main source of supply of oxygen to the Mediterranean, producing between 4 and 20 liters of oxygen per square meter in a day. l

Posidonia oceanica - Life cycle

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Summer

Winter

Autumn

Spring

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Summer landscape Meadows acquire whitish shades due to the large number of organisms (hydrozoans, bryozoans, mollusks, etc.) that colonize the leaves during the warmer months of the year. In the Posidonia oceanica meadows, these organisms found an ideal substrate that offers protection and food. At the same time, these colonizer organisms represent an attraction and a source of food for a multitude of species. In this season, facing the difficulty of the leaves to breathe and perform photosynthesis, Posidonia oceanica does not grow in height. Whitish appearance of Posidonia oceanica meadows due to organisms that colonize the surface of the leaves. Picture: Xisco Sobrado.

Autumn landscape The plant starts losing its leaves alongside with the animals and vegetable organisms, which have colonized the meadow. During this time, the bed banks appear on the beaches. These bed banks are vital to protect the coastline. Moreover, in sandy beaches during episodes of strong swell. In autumn, new leaves of an intense green color begin to sprout. These new leaves give the landscape appearance of freshness and cleanliness. The leaf growth continues until the beginning of spring. In this season, the flowering of the meadow also begins. If the flowering is very intense, there is a spectacular transformation of the landscape, ranging between deep green and yellowish colors. Stem with new leaves torn off by the storm and deposited on the beach. Picture: GEN-GOB Archive.

Winter landscape. During the winter the temperatures are still falling. This slows down the growth of the leaves started in autumn. At the same time, the flowering process of the meadow continues. During this season, it is when the meadow exhibit lush, with shorter leaves with intense green color. Curiously, winter is the most beautiful season to visit Posidonia oceanica meadows. Posidonia oceanica meadows showing the typical winter coloration. Picture: Xavier Mas.

Spring landscape In spring, the gradual increase in the temperature of the water accelerates the growth of the leaves. It is when the meadows are lush and resemble a submerged forest. At this moment, it is when the organisms start colonizing the meadow. Also, in this season the plant germinates, matures, and the first fruits emerges. These fruits are called sea olives. The fruits of Posidonoa oceanica arrrive at the beach washed by the waves. Picture: GEN-GOB Archive.