The Lung of the World Posidonia Ocenia

Flowering plants separated from algae by root, stem, leaf differentiation, and developed reproductive organs are included in the phanerogame branch1. They cover the floor in a carpet-like manner, that’s why they are called seagrass meadows and sea forests. Posidonia Oceanica is endemic to the Mediterranean Sea, and it is also known as Neptune grass or Mediterranean tapeweed. It has an important part of the ecosystem because it forms large underwater meadows. It covers an area of about 50.000 km2 on the Mediterranean coast. It is stated that it spreads in an area of 1150 km2 only on the coast of Franch2. It is located on the coasts of our country in the Mediterranean, Aegean, and partially in the Sea of Marmara. But it does not spread in the Black Sea region. In general, its geographical distribution is specified as the Mediterranean and Aegean Seas. For their living areas, they cannot survive below 0.33% salinity2. Because of the inability to find P. oceanica on some coasts is attributed to the lower salinity of the rivers and underground water sources that mix with the sea. It is shown as an indicator type of clean and sensitive area, especially since it is sensitive to pollution and anthropogenic effects; is used to define the status of regions.

P.oceanica populations are the most abundant in the ecosystem. Their great feature is that they are primary producers. Less than 10% of its primary production is utilized by herbivores. It mixes into the ecosystem as 24-85% of dead leaves3. These dead leaves accumulate at the base to form a mat layer, creating a great food source. While the mat layer formed at the bottom is very thin (1-2 cm) in the summer period, it is observed that the water-suspended materials increase in the autumn and winter seasons; It was determined that the mat layer with a thickness of 3-5 cm increased in the autumn period and became thicker (16-20 cm) in the winter period and finally medium thickness (10-12 cm)2. While marine organisms are rarely encountered in both dunes and rocky areas in both sampling regions, many sessile species such as sponges and macrobenthic algae are found in and around the areas where P. oceanica populations are found. It has been determined that sedentary organisms such as sea snails and sea urchins and nektonic organisms such as fish and squid live4.

Figure 1: Grass bed (Posidonia Oceanica).
Figure 2: Posidonia Oceanica with fishes.

P.oceanica, which is one of the endemic secondary plants of the Mediterranean, is an ecologically important aquatic plant with features such as forming the first link of the food chain, providing the CO2-O2 balance with photosynthesis, sheltering various flora and fauna species, and preventing erosion on the ground5,6. It is reported that many living species, especially macrobenthic algae, invertebrates, and fish, live in and around the P. oceanica population. However, there are few species that directly use these plants as food, and the sea turtles (Chelonia mydas), sea urchins (Paracentrotus lividus), and hungry fish (Siganus rivilatus, S. luridus) species can be given as examples4. According to a UNESCO report published in March by Carlos Duarte, a marine biologist at King Abdullah University in Saudi Arabia, one hectare of seaweed can absorb as much carbon dioxide as 15 hectares of rainforest5. Therefore, the importance of the Posidonia Oceanica on living phenomena is very great.

References:

  1. https://en.wikipedia.org/wiki/Posidonia_oceanica
  2. TURNA, İ.İ., ATİK, Ü. & YILDIRIM, U.G. (2017). Deniz çayırlarından Posidonia oceanica (L.) Delile’nın Alanya kıyılarındaki mevsimsel değişimleri.Süleyman Demirel Üniversitesi Eğirdir Su Ürünleri Fakültesi Dergisi, 13(1), 1-11.
  3. Tursi, F. Mastrototaro, F. Montesanto and G. Chimienti, “Monitoring the seagrass Posidonia oceanica to understand the effects of local disturbances in a marine protected area,” 2021 International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea), 2021, pp. 86-90, doi: 10.1109/MetroSea52177.2021.9611572.https://ieeexplore.ieee.org/document/9611572?arnumber=9611572
  4. UNESCO, Marine World Heritage: custodians of the globe’s blue carbon assets, https://unesdoc.unesco.org/ark:/48223/pf0000375565
  5. Dünya’nın Akciğeri Neptün Otu:Ağaçtan daha fazla karbondioksit depolayan mavi karbon ekosistemi.01/06/2021 https://tr.euronews.com/green/2021/06/01/dunyan-n-akcigeri-neptun-otu-agactan-daha-fazla-karbondioksit-depolayan-mavi-karbon-ekosisEuropean Zoological Journal, December 1, 2021, https://eds.p.ebscohost.com/eds/pdfviewer/pdfviewer?vid=4&sid=486628ed-93df-4ad7-93ac-a762a48dc4e4%40redis
  6. Seed photosynthesis enhances Posidonia oceanica seedling growth 30/12/2013. https://doi.org/10.1890/ES13-00104.1

Figure References:

  1. https://search.ebscohost.com/login.aspx?direct=true&db=imh&AN=imh2331854&site=eds-live&authtype=uid
  2. https://search.ebscohost.com/login.aspx?direct=true&db=imh&AN=imh1369801&site=eds-live&authtype=uid

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