Monitoring stations
The Mediterranean Conservation Foundation establishes monitoring stations to determine the distribution and development of the Posidonia oceanica species.
Species · Marine Species
Seagrass
Seagrass has the highest carbon storage capacity amongst all plant habitats in the world, at 2000 tonnes/ha.
Photo: Akdeniz Koruma Vakfı Arşivi
At a glance
Posidonia oceanica is endemic to the Mediterranean.
Seagrass has the highest carbon storage capacity amongst all plant habitats in the world, at 2000 tonnes/ha.
90% of seagrass habitats in the Mediterranean have been damaged.
The formation and development of seagrass meadows take many years.
The Mediterranean Conservation Foundation establishes monitoring stations to determine the distribution and development of the Posidonia oceanica species.
- 2000 ton/ha
- Carbon storage capacity of seagrass — the highest of all plant habitats
- %90
- Seagrass habitat damaged in the Mediterranean
- 94'ten fazla
- Species of micro and macro algae living on Posidonia oceanica leaves
About
Seagrass meadows are flowering plants that are widely scattered globally, and that have adapted to live rooted in the ocean floor (sediment). They form structures resembling roots, stems, and leaves, anchoring themselves to the seabed and producing their own food through photosynthesis with the help of sunlight. As a result of photosynthesis, they serve as a source of oxygen and nutrients in the oceans and provide critical spawning grounds for many fish species that lay their eggs among these plants. The formation and development of seagrass meadows take many years. Scientific studies have shown that attempts to artificially replant seagrass meadows have not been successful.
Read in depth
10-30 metreAverage depth to which Posidonia oceanica has receded along our coasts
- A wide temperature range
Posidonia oceanica meadows can support a relatively wide range of temperatures, as deduced from the wide latitudinal range of their distribution. Therefore, although no specific experiments have been conducted, from this latitudinal distribution we can deduce that the plant endures temperatures from approximately 10°C to 29°C.
- Light transparency
Since visibility is crucial for photosynthesis, Posidonia oceanica needs transparent, oligotrophic and oxygenated waters to survive. Its vertical distribution is limited by light. Posidonia oceanica can live within a narrow salinity range of 33-39‰, but populations in the Eastern Mediterranean Basin may also be living at higher salinity levels.
- Balance of sedimentation and erosion
Seagrass uses its roots to anchor itself to the seabed and to take up nutrients. Sediments must be relatively anoxic. It can grow on rocky or sandy bottoms. Muddy layers are unsuitable for its growth, because the seagrass cannot anchor itself to the ground and the water is too turbid for it to grow. In this respect, the balance between sedimentation and erosion greatly limits meadow development. Wave action is another important criterion: in shallow bays, seagrass can grow up to the water surface and form fringing reefs, but on open coasts it generally begins to grow a few metres below the surface.
Species living in seagrass meadows
- On the leaves of Posidonia oceanica
A conspicuous and complex epiphytic community lives on the leaves of Posidonia oceanica. Within this community there are more than 94 species identified as micro and macro algae. More than 44 species of sessile animals such as hydroids have also been identified, and more than 90 species of accumulating bryozoans have been found, which are also a common component of the leaf epiphytic community. The presence of the large fan mussel Pinna nobilis, listed as “Critically Endangered” (CR) on the Red List published by the International Union for Conservation of Nature (IUCN), is a good indicator of water quality and mechanical stability within the meadows (owing to its filter-feeding habits, long lifespan and slow growth).
- On the rhizomes
More than 70 algae species (mostly red algae), adapted to low light intensity, colonise Posidonia oceanica rhizomes. 185 species of molluscs and 120 species of crustaceans (copepods, decapods and amphipods) are the most abundant faunal groups in Posidonia oceanica meadows. Polychaeta are very abundant in the meadows; more than 180 species have been identified. Sponges are abundant in the rhizome substrate (more than 15 species). The meadows are also home to 16 species of sea cucumbers, which play a significant ecological role as sediment filterers.
- Refuge
Seagrass meadows provide a refuge for fish species to protect themselves. Many fish species live in the meadows until they reach adulthood. The herbivorous green turtle Chelonia mydas also feeds on seagrass.
Why are seagrass meadows important?
2000 ton/haCarbon storage capacity of seagrass — the highest of all plant habitats
Are seagrass meadows protected?
90% of seagrass habitats in the Mediterranean have been damaged.
What are the threats to seagrass meadows?
- Anchoring of boats
- Bottom trawling
- Sedimentation
- Erosion
- Eutrophication (seawater and sediment)
- Salinity increase (water treatment plants)
- Algal invasive species and invasive herbivores
- Climate change (seawater temperature)
- Marine pollution (plastic, ballast water, urbanisation, etc.)
- Coastal destruction
- Tourism pressure (artificial beaches, dredging, marina and port construction, etc.)
What can be done to protect seagrass meadows?
- Protection of the meadows against bottom trawling and other illegal fishing activities
- Establishing mooring buoy systems to prevent anchoring
- Management of marine litter (including sewage treatment systems)
- Taking action to control and combat invasive and alien species
- Preventing the introduction of organic matter
- Ecosystem restoration actions (e.g. no-take zones)
- Monitoring seagrass meadow areas
- Regulation and enforcement
References
- Akçalı, B., Kaboğlu, G., & Güçlüsoy, H. (2019). A review on Posidonia oceanica (Linnaeus) Delile coverage along the Turkish coasts until 2019. Journal of the Black Sea/Mediterranean Environment, 25(1).
- Pergent-Martini C., Rico-Raimondino V. & Pergent G. 1994. Primary production of Posidonia oceanica in the Mediterranean Basin. Marine Biology 120: 9–15.
- Monnier, B., Pergent, G., Mateo, M. Á., Clabaut, P., & Pergent-Martini, C. (2022). Quantification of blue carbon stocks associated with Posidonia oceanica seagrass meadows in Corsica (NW Mediterranean). Science of The Total Environment, 838, 155864.
- Pergent-Martini C., Pasqualini V., Pergent G. & Ferrat L. 2002. Effect of a newly set up wastewatertreatment plant on a marine phanerogam seagrass bed - A medium-term monitoring program. Bulletin of Marine Science 71: 1227-1236.
- Pasqualini V., Pergent-Martini C., Clabaut P. & Pergent G. 1998. Mapping of Posidonia oceanica using aerial photographs and side scan sonar : application off the Island of Corsica (France). Estuarine, Coastal and Shelf Science 47: 359-367.
- Díaz-Almela E. & Duarte C.M. 2008. Management of Natura 2000 habitats. 1120 *Posidonia beds (Posidonion oceanicae). European Commission.
- Marbà, N., Díaz-Almela, E., & Duarte, C. M. (2014). Mediterranean seagrass (Posidonia oceanica) loss between 1842 and 2009. Biological Conservation, 176, 183-190.
- Pergent-Martini, C., Pergent, G., Monnier, B., Boudouresque, C. F., Mori, C., & Valette-Sansevin, A. (2021). Contribution of Posidonia oceanica meadows in the context of climate change mitigation in the Mediterranean Sea. Marine Environmental Research, 165, 105236.
- Abadie, A., Pace, M., Gobert, S., & Borg, J. A. (2018). Seascape ecology in Posidonia oceanica seagrass meadows: Linking structure and ecological processes for management. Ecological Indicators, 87, 1-13.
- Montefalcone, M. (2009). Ecosystem health assessment using the Mediterranean seagrass Posidonia oceanica: a review. Ecological indicators, 9(4), 595-604.
- RAC/SPA - UNEP/MAP, 2014. Field Manual for Monitoring of Posidonia oceanica Seagrass Meadows (Posidonia Meadows). By Prvan M., Jakl Z. and Guala I. Ed. RAC/SPA - MedMPAnet Project, Tunis. 12 pages.
For this species
What we do
Ghost net clean-up
Through ghost net clean-up efforts, fishing gear and other solid waste that cover seagrass beds, reducing light and oxygen permeability, are being removed from this habitat.
Research on carbon stored in the roots
In addition, the Foundation investigates the amount of carbon that seagrass (Posidonia oceanica) stores in sandy sediment through its roots.
Anchoring warnings for boats
Through the Marine Ranger System, it warns boats not to anchor on seagrass beds within Marine Protected Areas.
Awareness-raising activities
Through its awareness-raising activities, it aims to increase knowledge about the species.
01Monitoring stations+
The Mediterranean Conservation Foundation establishes monitoring stations to determine the distribution and development of the Posidonia oceanica species.
02Ghost net clean-up+
Through ghost net clean-up efforts, fishing gear and other solid waste that cover seagrass beds, reducing light and oxygen permeability, are being removed from this habitat.
03Research on carbon stored in the roots+
In addition, the Foundation investigates the amount of carbon that seagrass (Posidonia oceanica) stores in sandy sediment through its roots.
04Anchoring warnings for boats+
Through the Marine Ranger System, it warns boats not to anchor on seagrass beds within Marine Protected Areas.
05Awareness-raising activities+
Through its awareness-raising activities, it aims to increase knowledge about the species.
