Posidonia oceanica, commonly known as Neptune Grass or Mediterranean tapeweed, is a marine flowering plant endemic to the Mediterranean Sea. Like other seagrasses, it forms large underwater meadows in the submerged photic zone of sheltered coastal waters (Pirog 2011). Due to its high rate of primary production and its ability to structure and stabilize the seabed, Neptune grass creates habitat for many other marine organisms and thus plays a significant role in littoral Mediterranean ecosystems (Gobert et al. 2006, Kendrick et al. 2005, Pergent et al. 1994).
Posidonia oceanica is one of the largest, slowest growing, and longest-lived plants. In a recent genetic study of 40 P. oceanica populations across the Mediterranean, Arnaud-Haond et al. (2012) found individual clones spanning up to 15 km (9.3 miles). Based on the plant's known growth rate, such individuals are likely to be thousands, possibly tens of thousands of years old (Arnaud-Haond et al. 2012) .
With their origin possibly dating back to the Pleistocene, some P. oceanica meadows have shown great resilience, persisting through great environmental changes over millennia. Yet, today P. oceanica populations are declining rapidly due to human-induced disturbances (Ardizzone et al. 2006, Duarte 2002, Marbà et al. 1996, 2005, Montefalcone et al. 2007, Waycott et al. 2009). Major threats include coastal construction (Badalamenti et al. 2006, Ruiz & Romero 2003), trawling (Gonzalez-Correa et al. 2005), fish farming (Díaz-Almela et al. 2008, Pergent-Martini 2006), and climate change (Marbà & Duarte 1997, 2009). Arnaud-Haond et al. (2012) warn that "the ancient meadows of P. oceanica are declining at a rate several hundred-fold faster (about 5%.yr−1, Marbà et al 2005, Waycott et al. 2009) than the rate over which they spread when forming (Doyle & Doyle 1987, Sintes 2006), a situation that this slow growing, long-lived species is poorly capable of recovering from."
Posidonia oceanica is endemic to the Mediterranean Sea. Posidonia oceanica is the dominant seagrass in the Mediterranean Sea covering about 50,000 km2 of coastal to offshore sandy and rocky areas to depths of 45 m.
Distribution in Egypt
Habitat and Ecology
Posidonia oceanica is a large, long-living but very slow-growing seagrass. Its shoots, which are able to live for at least 30 years, are produced at a slow rate from rhizomes which grow horizontally by only 1-6 cm each year. Over centuries the rhizomes form mats which rise up into reefs that help to trap sediment and mediate the motion of waves, thus clarifying the water and protecting beaches from erosion (Boudouresque et al. 2006).
Posidonia oceanica is a monoecious species, with male and female flowers in the same inflorescence. The biological characteristics of P. oceanica are not conducive to a rapid recolonization of dead matte: sexual reproduction is rare, natural reestablishment is not common, and horizontal growth of rhizome edges from a contiguous bed is very slow (Meinesz et al. 1991). For more detailed information, a synthesis of the current knowledge is available in Boudouresque et al. (2006).
The meadows composed of this species are considered the basis of the richness of Mediterranean coastal waters, due to the surface area they occupy and to the essential part they play at biological level in maintaining the coastal equilibrium and their concomitant economic activities (Boudouresque et al. 2006). The role of Posidonia oceanica meadows in marine coastal environments is often correctly compared to that of a forest.
Posidonia oceanica is an important habitat forming species and provides habitat for many species. Nursery grounds for the juveniles of many commercially important fishes and vertebrates, such as several species of the family Sparidae (e.g., Diplodus annularis), Serranidae (e.g., Serranus cabrilla), Labridae (e.g., Coris julis and Crenilabrus maculatus) and Scorpaenidae (e.g., Scorpaena scrofa and Scorpaena porcus), and the sea urchin Paracentrotus lividus. Posidonia oceanica is also grazed on by the Green Sea Turtle (Chelonia mydas). A recent study by Thomas et al. (2005) found that urchins have a relatively minor impact on the seagrass, while grazing by the fish Salpa salpa can outstrip locally the plants' leaf production.
Usually forming an extensive massive turf on sand, in deep seawater, abundant on sandy beaches.
Water temperature and chemistry ranges based on 384 samples.
Depth range (m): 1.6 - 7
Temperature range (°C): 16.269 - 16.269
Nitrate (umol/L): 1.692 - 1.692
Salinity (PPS): 37.969 - 37.969
Oxygen (ml/l): 5.382 - 5.382
Phosphate (umol/l): 0.229 - 0.229
Silicate (umol/l): 1.778 - 1.778
Depth range (m): 1.6 - 7
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Life History and Behavior
Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica
Arnaud-Haond S, Duarte CM, Diaz-Almela E, Marbà N, Sintes T, et al. (2012) Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica. PLoS ONE 7(2): e30454. doi:10.1371/journal.pone.0030454
Editor: Hans Henrik Bruun, University Copenhagen, DenmarkAbstract The maximum size and age that clonal organisms can reach remains poorly known, although we do know that the largest natural clones can extend over hundreds or thousands of metres and potentially live for centuries. We made a review of findings to date, which reveal that the maximum clone age and size estimates reported in the literature are typically limited by the scale of sampling, and may grossly underestimate the maximum age and size of clonal organisms. A case study presented here shows the occurrence of clones of slow-growing marine angiosperm Posidonia oceanica at spatial scales ranging from metres to hundreds of kilometres, using microsatellites on 1544 sampling units from a total of 40 locations across the Mediterranean Sea. This analysis revealed the presence, with a prevalence of 3.5 to 8.9%, of very large clones spreading over one to several (up to 15) kilometres at the different locations. Using estimates from field studies and models of the clonal growth of P. oceanica, we estimated these large clones to be hundreds to thousands of years old, suggesting the evolution of general purpose genotypes with large phenotypic plasticity in this species. These results, obtained combining genetics, demography and model-based calculations, question present knowledge and understanding of the spreading capacity and life span of plant clones. These findings call for further research on these life history traits associated with clonality, considering their possible ecological and evolutionary implications. The maximum size and age that clonal organisms can reach remains poorly known, although we do know that the largest natural clones can extend over hundreds or thousands of metres and potentially live for centuries. We made a review of findings to date, which reveal that the maximum clone age and size estimates reported in the literature are typically limited by the scale of sampling, and may grossly underestimate the maximum age and size of clonal organisms. A case study presented here shows the occurrence of clones of slow-growing marine angiosperm Posidonia oceanica at spatial scales ranging from metres to hundreds of kilometres, using microsatellites on 1544 sampling units from a total of 40 locations across the Mediterranean Sea. This analysis revealed the presence, with a prevalence of 3.5 to 8.9%, of very large clones spreading over one to several (up to 15) kilometres at the different locations. Using estimates from field studies and models of the clonal growth of P. oceanica, we estimated these large clones to be hundreds to thousands of years old, suggesting the evolution of general purpose genotypes with large phenotypic plasticity in this species. These results, obtained combining genetics, demography and model-based calculations, question present knowledge and understanding of the spreading capacity and life span of plant clones. These findings call for further research on these life history traits associated with clonality, considering their possible ecological and evolutionary implications.
Molecular Biology and Genetics
Barcode data: Posidonia oceanica
Statistics of barcoding coverage: Posidonia oceanica
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
Eutrophication (fertilizer from agriculture and urban waste) and pollution, especially in coastal regions that are heavily populated, is a problem. Fish farm activities and aquaculture affect surrounding Posidonia meadows. Only meadows greater than 800 m away from the fish farms showed no impact from the fish farming activity and meadows up to one km from large fish farms may be affected (Marba et al. 2006). Invasive species also compete for habitat (e.g., seaweeds species such as Caulerpa taxifolia and Caulerpa racemosa). Climate change will be an additional threat through warming of waters (in excess of 28°C) and erosion from sea level rise.
The lack of genetic variability and slow growth makes Posidonia oceanica less resilient to disturbance.
Posidonia oceanica is protected by EU legislation (Habitat directive), the Bern and Barcelona Conventions and national legislation (Spain, Algeria, etc.). Fishing regulations limit trawling activities near the shore (either above 50 m or a certain distance from the coast), which constitute an indirect protection measure for the species (EC Council Regulation N° 1967/2006 and national regulations).
Posidonia oceanica is present in various marine parks in the countries along the Mediterranean Sea (Green and Short 2003). Efforts have been made to prevent physical damage caused by trawler-fishing by placing artificial reefs, consisting of spiked concrete blocks, along certain stretches of the coast, and also by mounting a coastal watch to prevent illegal trawling.
Research into potential species conservation plans is needed, as is site protection and management, habitat restoration, increased awareness, and legislation at local, national and international levels.
Posidonia oceanica (commonly known as Neptune Grass or Mediterranean tapeweed) is a seagrass species that is endemic to the Mediterranean Sea. It forms large underwater meadows that are an important part of the ecosystem. The fruit is free floating and known in Italy as "the olive of the sea" (l'oliva di mare). Balls of fibrous material from its foliage, known as egagropili, wash up to nearby shorelines.
P. oceanica is a flowering plant which lives in dense meadows or along channels in the sands of the Mediterranean. It is found at depths from 1–35 metres (3.3–114.8 ft), according to water clarity. Subsurface rhizomes and roots stabilize the plant while erect rhizomes and leaves reduce silt accumulation.
The leaves are ribbon-like, appearing in tufts of 6 or 7, and up to 1.5 metres (4.9 ft) long. Average leaf width is around 10 millimetres (0.39 in). The leaves are bright green, perhaps turning brown with age, and have 13 to 17 parallel veins. The leaf terminus is rounded or sometimes absent because of damage. Leaves are arranged in groups, with older leaves on the outside, longer and differing in form from the younger leaves they surround.
The rhizome type stems are found in two forms: one growing up to 150 centimetres (59 in) beneath the sand and the other rising above the sand. All stems are approximately 10 millimetres (0.39 in) thick and upright in habit. This arrangement of the rhizomes eventually forms a mat; the surface contains the active parts of the plant, whereas the center is a dense network of roots and decomposing stems.
The flowering plant's common name is Neptune grass. In 2006 a huge clonal colony of P. oceanica was discovered south of the island of Ibiza. At 8 kilometres (5.0 mi) across, and estimated at around 100,000 years old, it may be one of the largest and oldest clonal colonies on Earth.
Range and habitat
This species is found only in the Mediterranean Sea where it is in decline, occupying an area of only about 3% of the basin. This corresponds to a surface area of about 38,000 square kilometres (15,000 sq mi). Posidonia grows best in clean waters, and its presence is a marker for lack of pollution. The presence of Posidonia can be detected by the masses of decomposing leaves on beaches. Such plant material has been used for composting, but Italian laws prohibit the use of marine algae and plants for this purpose.
The genus Posidonia is named after Poseidon, the Greek god of the seas, while oceanica refers to its former wide distribution. Carl Linnaeus gave the first botanical description of this species in Systema Naturae, although the genus was then named Zostera. The APG system (1998) and APG II system (2003) accept the genus as constituting the sole genus in the family Posidoniaceae, which it places in the order Alismatales, in the clade monocots. The Angiosperm Phylogeny Website concludes that the three families Cymodoceaceae, Posidoniaceae and Ruppiaceae form a monophyletic group. Earlier systems classified this genus in the family Potamogetonaceae or in the family Posidoniaceae but belonging to order Zosterales.
To date 51 natural products have been reported from P. oceanica, including natural phenols, phenylmethane derivatives, phenylethane derivatives, phenylpropane derivatives and their esters, chalkones, flavonols, 5-alpha-cholestanes, and cholest-5-enes. Many of the compounds reported for P. oceanica were, however, not detected by appropriate phytochemical methods and some most probably represent artifacts and are not genuine natural products of P. oceanica.
- Pergent, G., Semroud, R., Djellouli, A., Langar, H. & Duarte, C. 2010. Posidonia oceanica. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 9 January 2013.
- "Posidonia oceanica" (in Italian). "Dopo essere fecondato, in estate fa crescere e maturare il suo frutto, l’oliva di mare (si chiama così perché ha una forma arrotondata)."
- "Posidonia oceanis".
- "Portuguese scientists discover world's oldest living organism".
- Ibiza Spotlight (28 May 2006). "Ibiza's Monster Marine Plant". Retrieved 2007-05-09.
- Pearlman, Jonathan (7 February 2012). "'Oldest living thing on earth' discovered". The Telegraph. Retrieved 11 February 2012.
- Arnaud-Haond, Sophie; Duarte, Carlos M.; Diaz-Almela, Elena; Marbà, Núria; Sintes, Tomas; Serrão, Ester A.; Bruun, Hans Henrik. "Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica". PLoS ONE 7 (2): e30454. doi:10.1371/journal.pone.0030454. PMC 3270012. PMID 22312426.
- "Alismatales". Mobot.org. Retrieved 11 February 2012.
- Heglmeier, A; Zidorn, C (October 2010). "Secondary metabolites of Posidonia oceanica". Biochemical Systematics and Ecology (Amsterdam, The Netherlands) 38 (5): 964–70. doi:10.1016/j.bse.2010.07.001. ISSN 0305-1978.
- This article incorporates information from
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