Bodrum Underwater Park Project

Seagrasses are flowering plants that have established root, stem, and leaf systems underwater. They form extensive beds on the seabed, where they photosynthesize and provide oxygen and nutrients to the sea. While originally living on land, these plants have adapted to aquatic life and exhibit characteristics of terrestrial plants, such as flowering.

Seagrasses are considered the “lungs” of the marine ecosystem. They enrich the water by producing 14–20 liters of oxygen per square meter per day. They also create habitats, breeding grounds, and feeding areas for many fish, crustaceans, and other marine creatures. They weaken waves and currents, prevent coastal erosion, clarify the water, and sequester atmospheric carbon by burying it in the soil with their deep roots. These ecosystem services play a critical role in combating climate change while supporting sustainable fisheries.

Seagrasses, primarily the species Posidonia oceanica, live only in the Mediterranean Sea and surrounding warm seas. In Turkey, the known distribution of P. oceanica is limited to the area around the Marmara Sea Islands, while it covers our Aegean and Mediterranean coasts as far as Iskenderun. Other seagrass species (Cymodocea nodosa, Zostera marina, Z. noltii) can be found in all our seas, including the Black Sea. On the other hand, seagrasses are widespread along the coasts of all Mediterranean countries such as Spain, France, Italy, Greece, and North Africa. Posidonia oceanica is found to cover approximately 25% of the Mediterranean coast.

Yes, seagrass meadows have significantly decreased globally in recent years. For example, in the Mediterranean, their distribution or area has declined by more than 30% in 50 years. The biggest threats are human-induced factors such as coastal development, pollution (waste discharge), bottom trawling, boat anchoring, and agricultural fertilizer runoff. Along with these factors, increasing nutrient salt concentrations, harmful invasive algae (e.g., Caulerpa racemosa), and invasive animals reduce the competitiveness of seagrass meadows. In Turkey, due to these reasons, Posidonia oceanica has shifted the bottom depth limit by several meters, and it has been determined that the healthy meadow condition index in Gökçeada has decreased from "good" to "moderate". Although seagrass meadows are officially protected (EU Habitat Directive, Bern Convention, Law No. 1380, etc.), they are still threatened by local pollution and degradation.

Everyone can contribute to protecting seagrass meadows. First, boats should be moored in clean sediment areas instead of buoyed moorings, and anchoring bans should be observed. Preventing marine pollution, not dumping waste into the sea, and reducing domestic/agricultural waste are also essential. You can also provide volunteer support through diving, cleaning activities, and scientific observation studies. You can also contribute to the protection of seagrass meadows by participating in awareness campaigns, informing your surroundings, and donating to conservation projects.

The Origin of Seagrasses

Seagrasses have a very long scientific and cultural history. The name of the species Posidonia oceanica, which is widespread in the Mediterranean today, comes from Poseidon, the god of the seas in ancient Greek mythology. This naming shows that seagrasses were perceived as having a strong connection with the sea even in antiquity.

Ancient Greek and Roman sources mention fibrous plant remains washed ashore. These remains are thought to be clumps of seagrass leaves shaped by waves, which we now call "Posidonia balls." Archaeological and written indirect evidence exists that these fibrous materials were used in ancient port cities for insulation, filling, and even animal bedding.

Although the concept of "seagrass" was not defined in its current ecological sense in antiquity, it is known that people observed and benefited from these plants. This shows that seagrasses have been part of the human-nature relationship for thousands of years.

What are the functions of seagrasses in the ecosystem?

Oxygen Production and Habitat

Photosynthetic seagrasses enrich the water with oxygen through their stems and leaves. They also provide habitat, breeding grounds, and feeding areas for many organisms, from schools of reptiles and fish to crustaceans.

Prevention of Waves and Erosion

Extensive seagrass beds weaken wave energy, aiding in water refraction, and clarify the water by holding underwater sediments with their roots. Dead leaves washed ashore form natural barriers, slowing coastal erosion. Thus, seagrasses protect coastlines primarily from the destruction caused by waves and storms.

Biodiversity and Economic Contribution

Seagrass meadows are a major producer in the Mediterranean and provide habitat for millions of juvenile fish. These areas contribute to sustainable fisheries by serving as breeding grounds for species important to the fisheries. The highly biodiverse meadow ecosystems support the lives of many protected species.

Carbon Sequestration

Seagrasses, with their thick rhizomes and foliage, form blue carbon sinks. Measurements in the UK show that one hectare of Posidonia beds traps an average of 1,000 tons of carbon dioxide per year. This makes them even more effective than forests (15 times more effective than the Amazon rainforest) in combating climate change.

Distribution in Türkiye and Neighboring Countries

Along the Turkish coasts, Posidonia oceanica has a wide distribution in the Mediterranean and Aegean Seas. In Türkiye, P. oceanica is absent from the Black Sea; in the Sea of Marmara, it is found only in limited areas around the Marmara Islands. It is widespread along our Aegean and Mediterranean coasts, from Adana/Mersin to the Gulf of Iskenderun (approximately 14,500 hectares of registered area). Other seagrass species in our country (C. nodosa, Z. marina, Z. noltii) are found throughout our seas, including the Marmara and Black Sea coasts from Gökçeada to Ordu.

Outside of the Turkish mainland, seagrasses are endemic to the Mediterranean Sea, not extending into the Eastern Atlantic. These plants range from the far Atlantic coast of Spain to France, Italy, all the Italian islands, Greece, Turkey, and North Africa (Tunisia, Algeria, Libya). The best-preserved Posidonia meadows in the Mediterranean are concentrated in western Mediterranean islands such as Ibiza and its surroundings. The extensive, dry Mediterranean coasts, with their clear and salty waters, provide an ideal habitat for this plant. Therefore, Posidonia oceanica is the main and most widespread seagrass species throughout the Mediterranean region, including Turkey.

Seagrass Conservation Efforts

Restricting anchoring and mooring activities in areas with dense seagrass beds, and installing buoy systems.

Coastal development, dredging, and landfill activities should be monitored through scientific impact assessments.

Strengthening wastewater management and plastic and solid waste control efforts to reduce marine pollution.

Conducting long-term scientific monitoring and mapping studies to track the distribution and health of seagrass meadows.

Expanding marine literacy and awareness-focused training programs for local people, fishermen, and students.

Implementing seagrass restoration and revitalization practices in damaged areas based on scientific criteria.

ECOLEGACY MEDİTERRANEAN