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Grass in the sea?

Nimashi Amaleeta
Ever heard of grasses growing in the sea-bed? But, believe it or not, there are plenty. Letís find out.
They are called sea-grasses because they resemble grasses growing on land. Like terrestrial plants, sea-grasses have leaves, roots, conducting tissues, flowers and seeds, and produce some of their food via photo-synthesis. Unlike terrestrial plants, however, sea-grasses do not possess the strong, supportive stems. Sea-grass blades are supported by the natural buoyancy of water, remaining flexible when exposed to waves and currents.
Sea-grasses form extensive beds or meadows under water. They can be either mono-specific (made up of one species) or multi-specific (where more than one species co-exist). In temperate seas, usually one or a few species dominate the environment, whereas tropical beds usually are more diverse, with up to 13 species recorded in the Philippines.
Like all other green plants, sea grasses also photo-synthesize. They need sunlight to grow. Therefore, they are limited to growing submerged in the upper marine zone and most occur in shallow and sheltered coastal waters, anchored in sand or mud. They undergo pollination while submerged and complete their entire life cycle under-water. There are about 60 species worldwide.
Their importance?
Sea-grass beds are highly diverse and productive ecosystems, and can harbour hundreds of associated species from marine genera. These include juvenile and adult fish, epiphytic and free-living macro- and micro-algae, shell-fish, bristle, cylindrical worms. Juvenile stages of many fish species spend their early days in the relative safety and protection of sea-grasses.
The complexity of sea-grass habitats is increases when several species of sea-grasses grow together. Many hundreds of species feed on sea-grasses ocean-wide, including dugongs, manatees, fish, geese, swans, sea-urchins and crabs.
Sea-grasses are sometimes labelled eco-system engineers, because they partly create their own habitat. The leaves slow down water-currents, increasing sedimentation, and the sea-grass roots and shoots stabilize the seabed. Their importance for associated species is the shelter they provide and for their extraordinary high rate of primary production.
Threats
Sea-grasses are subject to a number of stresses such as storms, excessive grazing by sea creatures, disease, and human threats due to pollution, decreasing water clarity, excessive nutrients in run-offs, by propellers and scarring.

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