Why are seagrasses important?
Primary production: They produce more vegetal matter than tropical forests.
Source of food: They are at the base of numerous food chains.
Biodiversity hot spots: They provide shelter to several hundred of macro-invertebrates, and algae.
Water oxygenation: They generate over 10 litre of oxygen per m2 per day.
Protection from predators: They offer a refuge beneath the foliar shoots.
Reduction of water movement: They reduce wave and current force.
Stabilization of soft bottoms: They trap and fix sediment.
Fight against erosion in beaches: They function as barriers in the littoral zone due to the accumulation of dead leaves.
Spawning areas and nurseries: They promote the reproduction of fish and crustaceans.
Habitats for numerous species: They provide shelter for economically important fish, allowing sustainable fishing activities.
Why do seagrass beds disappear?
1- Coastal development
They are threatened by port facilities, recreational activities, and pollution.
2- Urban and industrial waste
Due to domestic/industrial discharges, they can’t utilize the light in the water column for photosynthesis.
3- Mechanical damage
Their rhizomes are removed from sediment by fishermen’s trawls and boat anchors.
They compete with epiphytic algae covering their leaves caused by nutrient increases from fish farming, agriculture and urban activity.
Studied seagrass beds on the Turkish coast
Mediterranean coastline, Turkey presents convenient conditions for the development of large seagrass beds.
Studies were conducted at the Gökçeada Island and Mersin Area, in collaboration with the Istanbul University Fisheries Faculty, and the Middle East Technical University Institute of Marine Sciences, respectively, confirmed the importance of these meadows.
The Mersin area has a particular importance as it corresponds to the limit of North-Eastern extension of the Posidonia meadows in the Mediterranean Sea. This geographical limit of extension of the species seems related to a too high water temperature during the summer season,
whereas the meadows in Gökçeada Island seem to be under the influence of water masses from the Black Sea (low water salinity) and the Mediterranean Sea (high water salinity).
Action Plan for the Conservation of Marine Vegetation in the Mediterranean Sea
Adopted in 1999, by the Contracting Parties to the Barcelona Convention, this Action Plan has several objectives:
*To implement measures for the management and protection of marine plant species
*To fight against the destruction of these formations, accepted to be key components of littoral ecosystems
*To ensure the preservation of these formations in characteristic areas.
The implementation of this Action Plan has been entrusted to the Regional Activity Centre for Specially Protected Areas (UNEP/MAP-RAC/SPA).
The MedPosidonia Project
In the framework of this Action Plan, a sub-regional project for the inventorying, mapping and monitoring of Posidonia meadows in Algeria, Libya, Tunisia and Turkey (MedPosidonia Project) has been implemented over a three-year period (2006-2008), thanks to the financial support of the Total corporate Foundation.
The Project aims at collecting information on the presence and evolution of Posidonia meadows in selected sites, and training national teams to make them able to pursue these tasks in the future.
Posidonia oceanica (Linnaeus) Delile
Common names: Seagrass (En), Deniz çayırı (Tr)
Distribution: An endemic marine phanerogame of the Mediterranean and Aegean Seas.
Habitat: It forms extensive beds in the infralittoral bottom of the basin. Most commonly on mobile and soft substrates, such as coarse sand, sometimes mixed with mud, but also on rocky sea bottoms. The plant needs strong light. The two limiting factors for the growth of P. oceanica are transparency of water and depth. These extend from the surface to depths of around 30-35 meters, reaching 40 meters (depending on water limpidity), in particularly clear waters. It is stenohaline (tolerance regarding salinity), disappears near river mouths and is completely absent in freshwater areas. Broken leaves of this seagrass may form brownish soft balls (sea-balls), when mixed with sand grains and rolled by the waves.
Life history: The primary mechanism of reproduction is vegetative from perennial rhizomes. Flowering and fruiting is considered uncommon.
Dimension: Leaves are narrow and flat, about 1 cm in width and 30 cm or more in length.
Morphology: P. oceanica is one of the most important primary producer in the Aegean and Mediterranean Seas. It consists of a root named rhizome and leaves. The rhizomes develop horizontally and vertically. Posidonia meadows are considered as the most important ecosystems along the coasts. It forms a suitable substrate and shelter area for other macro and microalgae and it constitutes a habitat for many other species. It is the main biodiversity reservoir in the Mediterranean (with the Coralligenous community); the meadows weaken the hydrodynamic force (waves swell). This species is under protection by law in Turkish waters. However, they are declining due to coastal infrastructure; bottom trawling, beach set net, gill nets, anchoring, turbidity, and pollution. Because of the particular importance of Posidonia meadows in the Mediterranean, their conservation is considered to be one of the main priorities of the present Action Plan.
SEAGRASSES ARE THE PRIMARY PRODUCERS AND BIODIVERSITY HOTSPOTS OF THE MEDITERRANEAN.
SEAGRASSES (Posidonia oceanica) ARE IMPORTANT ENDEMIC SPECIES IN THE MEDITERRANEAN.
Since 1950’s, seagrasses and seagrass habitats have been intensely studied for their ecological importance and rich biodiversity. First studies have focused on the biology, ecology and reproduction of Posidonia ocenica but recently, due to increasing threats, conservation of the species and their habitats gained importance. Today, this species is used as a bioindicator to monitor environmental quality (Dural et al. 2013).
Healthy Seagrasses, sheltering various organisms from invertebrates to fish, are indicators of a good ecological balance.
Posidonia oceanica (L.) Delile forms seagrass meadows and is a long-lived, flowering species with subsurface rhizomes. As one of the few flowering marine plants, it consists of roots, rhizomes and leaves with fruits and flowers that bloom in spring. It has gained reputation as the lung of the sea as it can produce more than 5000 litres of oxygen per square metre per year in daylight (Dural et al. 2013). Seagrass meadows are important habitats as they are home to countless marine organisms.
Fruit of the flowering plant, Posidonia oceanica
Endemic to the Mediterranean, Posidonia oceanica is distributed throughout the coastal regions of the Mediterranean and the Aegean seas in our country. The two populations found near the lower-salinity dardanelles strait, coast of south Marmara (Paşalimanı Island and Kapıdağ Peninsula) are genetically isolated populations with distinct genotypes (Meinesz et al., 2009 and Cirik and Akçalı, 2013).
Seagrass meadows house a large biodiversity as well as high oxygen production capacity. Studies have detected large quantities of Bryozoon species living on seagrass leaves and rhizomes. Despite being affected by factors such as region, leaf width and depth, approximately a hundred species of Bryozoons have been detected (Koçak, 2013). 87 taxa of macroalgea within the seagrasses in Çanakkale and the Marmara Sea (Taşkın and Öztürk 2013), 394 Polychaeta consisting of 316 species in the Aegean Sea, 55 species in the Meaditerranen and 242 species in Northern Cyprus (Çınar, 2013), 251 species of Molluscs (Doğan et al. 2013), 273 Crustacean species (Katağan and Bakır, 2013), 14 Sipuncula species on our coasts and along Northern Cyprus (Açık, 2013) and 49 species of fish in the Posidonia meadows along the coasts of Gökçeada were recorded, surpassing numbers in rocky and muddy bottoms (Keskin et al. 2013). Posidonia oceanica, in adition to the rich biodiversity it hosts, prevents bed erosion in coastal zones and housing a rich coastal fauna in its leaves and rhizomes by washing ashore and forming banquettes on the coasts postmortem.
HOW LARGE IS THE AREA COVERED BY TURKEY’S SEAGRASS MEADOWS?
Posidona oceanica seagrass meadows, also known as ‘noodles’, are not found in the Black Sea. They are distributed in a small area around Marmara islands in the Marmra Sea, along the coasts of the Aegean Sea and in the Mediterranean up until Iskenderun.
Below is the regional data published in an article of our journal. The article approximates a total area of 14 486.20 hectares of seagrass meadows but it’s likely that this number will increase and we’ll have more accurate data with further studies. Possessing an abundance of seagrass meadows and better conservation practices will lead to healthier marine environments.
Table 1: Locations of seagrass medows along Turkey’s coastlines by 2019 (Akçalı et al. 2019)
Seagrass meadows along Turkish coasts (Akçalı et al. 2019)
Fisheries equipment that uses dragging cause great harm to Posidonia medows and marine life dwelling within.
Biodiversity-rich seagrass meadows are facing various threats in our wters just like the rest of the Mediterranean. Not only bad anchoring practices, fisheries with dragnets and pollution, but also anthropological and industrial pollution are important threats to these habitats. Habitat competition with the invasive Caulerpa racemosa var. cylindracea due to global climate change is another novel threat (Cavas and Mert, 2013). Posidonia oceanica, recognized as an important habitat within the Mediterranean ecoregion in the EU Marine Strategy Framework Directive, is being studied and under protection via action plans through various institutions and organizations including RAC/SPA. Turkey is party to the biodiversity-related Barcelona and Bern Conventions as well as CITES, and this species is under protection according to the law no. 1380 of fisheries circular. Sadly, research results from the MedPosidonia program indicate that seagrass meadows have receded by 3,21 metres within the last 8 years. As a result of this study, Posidonia Biotic Index for the pilot site, the coasts of Gökçeada, has been demoted from ‘Good’ to ‘Moderate’ (from 0,63 to 0,41). Recent increase in anthropological pressure is presumed to have caused this (Güreşen et al. 2019).
Invasive species Caulerpa racemosa var. cylindracea occupy the same habitats as seagrass meadows and threaten seagrasses as they outcompete Posidonia (a). Pollution is another threat for seagrass meadows (b).
Posidonia oceanica leaves and rhizomes that drift ashore and accumulate into banquettes host a large fauna.
LET’S WORK TOGETHER
Please send us your photos, videos showing potential threats, and remarks about Posidonia meadows. Help us protect the lungs of our seas.
Let’s work together to protect seagrass meadows. Protecting this species endemic to the Mediterranean will support sustainable fisheries and conserve biodiversity. Millions of young marine organisms will have a chance at life. Oxygen production will increase. We will have valuable reinforcements in our fight with climate change.
Ship captains, please avoid Posidonia meadows while dropping anchor. Prefer buoys if possible.
Stop the coastal zones from being destroyed, do not dump construction material in marine environments. Coastal zones are the most abundant and fertile areas of marine environments and these light-filled regions are where the seagrass meadows live. These areas are also under great anthropological pressure and need ample protection.
Turkish Marine Research Foundation has organized a national workshop about the seagrass meadows, main habitats of the Mediterranean, for the first time in 2013. A proceedings book with all the aforementioned information and more has been published and is available for download for free from our website.
REFERENCES (TO BE UPDATED AS NECESSARY)
Açık, Ş.2013.Sipunculans associated with Posidonia oceanica (L.) Delile on the coasts of Turkey and Northern Cyprus. Aktan Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 132-143.
Akçalı, B., Kaboğlu, G., Güçlüsoy, H.2019. Posidonia oceanica (Linnaeus) Delile coverage along the Turkish coasts until 2019. J. Black Sea/Mediterranean Environment. Vol. 25, No. 1: 115-124
Cavas, L., Mert, N.2013. Industrial researches on Posidonia oceanica (L.) Delile. Aktan Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 160-177.
Cirik, Ş. Akçalı, B.2013. Distribution of Posidonia oceanica (L.) Delile in the Sea of Marmara. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp:37-47.
Çınar, M.E. 2013. Polychaetes (Annelida: Polychaeta) associated with Posidonia oceanica (L.) Delile along the coasts of Turkey and Northern Cyprus. Turkey. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 77-95.
Doğan. A., Öztürk, B., Önen, M., Bakır, B.B. 2013. Molluscs associated with Posidonia oceanica (L.) Delile on the coasts of Turkey. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 96-114.
Dural, B., Aysel, V., Demir, N .2013. Posidonia oceanica (L.) Delile on the coasts of Turkey. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp:1-19.
Güreşen, A., Güreşen, S.O., Sarı, E., Pergent, G., Aktan, Y. 2019. Regression Trend of Posidonia oceanica in a pilot region (Turkey) ithin the Monitoring Programme the Medposidonia. UNEP/MAP – SPA/RAC, 2019. Proceedings of the 6th Mediterranean Symposium on Marine Vegetation (Antalya, Turkey, 14-15 January 2019). LANGAR H., OUERGHI A., edits, SPA/RAC publi., Tunis, pp:59-63. ISBN 978-9938-9574-4-0
Katağan, T., Bakır, K.2013. Crustaceans associated with Posidonia oceanica (L.) Delile on the coasts of Turkey. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 115-131.
Keskin, Ç., Oral, M., İnanmaz, Ö.E. 2013. Juvenile fish assemblages around Gökçeada Island (North Aegean Sea, Eastern Mediterranean): Posidonia oceanica (L.) Delile meadows, rocky and bare sand areas. Aktan Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 144-152.
Koçak, F. 2013. Posidonia oceanica (L.) Delile epiphytes with particular reference to bryozoans. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 58-67.
Meinesz, A, Cirik, Ş¸, Akçali, B. Javel, F., Migliaccio, M. Thibaut , T. Yüksek, A, Procaccini, G. 2009. Posidonia oceanica in the Marmara Sea. Aquatic Botany 90: pp: 18–22
Taşkın, E…, Öztürk, M. 2013. Epiphytic macroalgal assemblages of Posidonia oceanica (L.)Delile in Turkey. Aktan, Y., Aysel, V. (Eds.) First National Workshop on Posidonia oceanica (L.) Delile on the Coasts of Turkey. Published by Turkish Marine Research Foundation, istanbul, Turkey. Publication Number: 39. pp: 68-76.