Biology of Posidonia
Gobert, S.; Cambridge, M.L.; Velimirov, B.; Pergent, G.; Lepoint, G.; Bouquegneau, J.-M.; Dauby, P.; Pergent-Martini, C.; Walker, D.I. (2006). Biology of Posidonia, in: Larkum, A.W.D. et al. (Ed.) Seagrasses: biology, ecology and conservation. pp. 387-408
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| Trefwoorden |
Biology
Flora > Weeds > Marine organisms > Seaweeds > Sea grass
Posidonia König, 1805 [WoRMS]
Marien/Kust |
| Auteurs | | Top |
- Gobert, S., meer
- Cambridge, M.L.
- Velimirov, B.
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- Pergent, G.
- Lepoint, G., meer
- Bouquegneau, J.-M., meer
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- Dauby, P., meer
- Pergent-Martini, C.
- Walker, D.I.
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| Abstract |
The nine species of Posidonia occur in two separate biogeographic regions: the Mediterranean Sea and the temperate southern coasts of Australia. Probably separated during the Late Eocene, Mediterranean and Australian species of Posidonia show large divergences in the DNA sequences and in shoot phenology and growth characteristics. They are all perennial plants, with linear leaves attached to a leaf-sheath which remains underground after the leaf-blade has been shed. The genus consists of large seagrasses with long leaves, and low rates of leaf and shoot turnover compared to smaller, fast growing seagrasses. They are monoecious, and have hermaphrodite inflorescences without a perianth. They inhabit exposed to moderately sheltered areas, in nutrient-poor waters with low tidal ranges. They colonize a great range of depths (0-45 m) and can settle on fine sand to rocky substrate. Species of Posidonia have high biomasses, with distinct seasonal variations in productivity and are influenced by light, temperature, nutrients, and water movement. Despite their high biomass, species of Posidonia appear to be a minor food source, as direct grazing is relatively unimportant but the presence of Posidonia can greatly alter species diversity and food webs by the provision of substrata for other organisms to settle and grow on. Posidonia meadows are regressing in many regions as a direct result of anthropogenic activities. Pollution and nutrient enrichment have been linked to impacts such as overgrazing, shading of seagrass leaves by excessive growth of epiphytic algae or phytoplankton. Deleterious effects are often difficult to detect in time: the health status of the interconnected Posidonia shoots, generally expressed in terms of biomass and production, does not directly reflect the environmental degradation, and by the time Posidonia is showing signs of regression, the rest of the ecosystem is already largely affected. The transplantation of these long-live species is slow and costly, and it is wiser to ensure their preservation by protection, rather than by the difficult process of ecosystem restoration. |
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