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Seagrass medow

Seagrass may be 'uncharismatic' but it still needs protecting

It may be not be as visible as tropical rainforests or wetlands but seagrass plays a vital role in the global ecosystem, filtering pollution and providing food to fish.

Whilst it’s commonly accepted that the world’s coastal and ocean ecosystems are at risk from the activities of man, uncharismatic habitats, namely ‘seagrass meadows’, are often forgotten about and marginalised in conservation agendas.

Seagrasses survive in a range of conditions, from the upper estuarine to marine environments, and are of relatively few species globally (about 70). These flowering plants that grow in the near-shore environment of most of the world’s continents, although not extremely biodiverse in their own right, support a vast array of biodiversity. 

They also provide a range of services to mankind. Amongst these biodiverse communities are a multitude of species that are classified as endangered, vulnerable or threatened with extinction (IUCN Redlist), including species of seahorse, turtle and dugong.

Ecologest Oct 2010

Seagrass the natural alternative to carpet

Seagrass is a strong resistant floor covering that is grown in paddy fields in china and during the growing season, the fields are flooded with sea water - once harvested and dried it is spun into yarn which is used to make carpets.

The yarn has impermeable property's and so it is very hard to dye - so in most cases it comes in it natural green colour or a slight brown shade

Most seagrass has a latex backing this makes the floor covering more durable and also stops any adhesive that is used durring the installation from coming through

Being a natural product there can be inconsistencies in colour and the weave - similar to knots found in wood this is normal and is considered part of its natural charm

Sea grass is woven into a few styles - natural weave herringbone both in standard and fine versions and a chunky basket weave the herringbone is also available with a coloured weft of sisal that brings colour to the seagrass

Seagrass is recommended for medium domestic and light contract situations and can be laid throughout your home -but please note - office roller chairs tend to dig into the weave and damage the flooring in a very short period of time - if you do have a roller chair in the room where your seagrass is being installed.

 Seagrass matting


These enormous vegetarians can be found in warm coastal waters from East Africa to Australia, including the Red Sea, Indian Ocean, and Pacific.

Dugongs are related to manatees and are similar in appearance and behavior— though the dugong's tail is fluked like a whale's. Both are related to the elephant, although the giant land animal is not at all similar in appearance or behavior.

Dugongs graze on underwater grasses day and night, rooting for them with their bristled, sensitive snouts and chomping them with their rough lips.

These mammals can stay underwater for six minutes before surfacing. They sometimes breathe by "standing" on their tail with their heads above water.

Dugongs spend much of their time alone or in pairs, though they are sometimes seen gathered in large herds of a hundred animals.

Female dugongs have one calf after a yearlong pregnancy, and the mother helps her young reach the surface and take its first breath. A young dugong remains close to its mother for about 18 months, sometimes catching a ride on her broad back.




You are here: Home > Marine Science > Marine Ecology > Marine Habitats > Seagrass


Seagrasses are not seaweeds but flowering plants that can live fully immersed in seawater. They are found in a few shallow sheltered bays and estuaries around our coasts (UK). They have long grass-like leaves that can be over a metre (3 feet) in length and form vast dense green meadows under the sea. Because they grow in the shallows close to the shore they are very vulnerable to damage by human activities.

Unlike algae which evolved in the sea, seagrasses have evolved from land plants which have colonised the margins of the oceans. Because these plants must photosynthesize, they are limited to growing submerged in the photic zone, and most occur in shallow and sheltered coastal waters anchored in sand or mud bottoms. They undergo pollination while submerged and complete their entire life cycle underwater - they have waterproof pollen!

Adaptations to Colonize the Sea

The colonization of the sea required a number of key adaptations including blade or subulate leaves with sheaths, fitted for high-energy environments;  hydrophilous pollination, allowing submarine pollination (except for the genus Enhalus) and subsequentpropagule dispersal; and extensive lacunar systems allowing the internal gas flow needed to maintain the oxygen supply required by their below-ground structures in anoxic sediments. Seagrass species are all clonal, rhizomatous plants, a necessary adaptation for angiosperm growth in the high-energy marine environment. The rhizome is responsible for the extension of the clone in space, as well as for connecting neighboring ramets, thereby maintaining integration within the clone. The growth rates of seagrass rhizomes vary from a few centimeters per year in the larger, slow growing species, to more than 5 m yr-1 in the smallest species. These horizontal extension rates result in estimated times to develop seagrass meadows ranging from less than 1 year, for fast-growing species (HalophilaSyringodium and Cymodocea species), to centuries for the slowest growing ones (e.g.Posidonia oceanica, phto below)

Seagrass Marine Algae
Complex root structure to anchor plant in the sediment, and extract nutrients and minerals Simple holdfast to anchor to hard substrate such as rocks or shells
Photosynthesis restricted to cells in leaves Photosynthesis undertaken by all cells
Transport minerals and nutrients in aerenchyma and the lacunae (veins) Uptake of minerals and nutrients from water column via diffusion
Reproduction via flowers, fruits and seeds Reproduction via spores


Seagrasses are sometimes labelled ecosystem engineers, because they partly create their own habitat: the leaves slow down water-currents increasing sedimentation, and seagrass  the  roots  and rhizomes stabilize the seabed.

Their importance for associated species is mainly due to provision of shelter (through their three-dimensional structure in the water column), and for their extraordinarily high rate of primary production.

As a result, seagrasses provide coastal zones with a number of ecological benifits such as fishing grounds, wave protection, oxygen production and protection against coastal erosion.

Seagrass meadows account for 15% of the ocean’s total carbon storage. 

Seagrasses were collected as fertilizer for sandy soil. This was an important activity in the Ria de Aveiro, Portugal, where the plants collected were known as moliço.

In the early 20th century, the French and to a lesser extent the Channel Islands used seagrasses as a mattress (paillasse) filling, and it was in high demand by French forces during World War I. It was also used for bandages and other tools.

Currently seagrass is being used in carpets and furniture woven like rattan.

Seagrass id diagram
Click on image to go to seagrass id

Posidonia oceanica meadow in the NW Mediterranean.


Why are they so important?

Seagrass meadows have long been recognised as an important habitat for marine wildlife. Underwater, the dense cover of leaves acts as a nursery for juvenile fish and crustaceans, like shrimps and crabs, and provide shelter from strong currents and predators. Seahorses favour these areas and anchor to the plants using their tails. These elusive creatures, although rare, are believed to live in meadows around the South East of England.

As well as providing havens for certain species, seagrass is food for birds like brent geese, teal and swans especially when it is exposed at low tide. Its dense network of roots and rhizomes also acts to bind the sediment together. In this way seagrass beds can stabilise areas of sand or mud and act to protect the coastline from erosion.

Tropical seagrasses are important in their interactions with mangroves and coral reefs. All these systems exert a stabilizing effect on the environment, resulting in important physical and biological support for other communities.

What are the threats to Seagrass?

Seagrass can be seriously damaged by coastal development and pollution, but people also damage the seagrass by:

Mooring in it - anchors pull up roots, allowing storms and currents to wash away large areas,

Travelling at high speed over it - boat propellers, keels and jet ski jets can cut through the leaves and roots, scarring and killing the seagrass.

Discharging waste and rubbish over it - waste in the water cuts out light and allows algae to smother the seagrass.

Fishing with scallop dredges and other mobile fishing gear through it - this breaks up the seagrass bed.

Using gill and tangle nets in the seagrass - the footropes, weights and anchors can damage the seagrass.

Walking on the seagrass - this tramples the plants and breaks the leaves.
How you can help

Don’t anchor over the seagrass beds - anchor on sand or raft up.

Don’t travel at high speed with speedboats or jet skis over shallow seagrass areas at low tide - watch out for seagrass and observe speed restrictions.

Don’t discharge waste or rubbish into the sea - use proper disposal sites.

Don’t use scallop dredges or other mobile fishing gear in seagrass areas - observe voluntary
‘no scalloping’ areas.

Don’t set nets over the seagrass - set nets outside the seagrass beds; this also avoids
overwintering diving bird areas.

Don’t walk on the seagrass or dig for bait in it - keep to the sand.

What is the Solent Seagrass project?

Seahorse by Colin Froud


seahorses mating


This project has been studying seagrass around the coasts of Hampshire and the Isle of Wight to learn more about its distribution and the health of the local populations. In partnership with Southampton's National Oceanography Centre and with the help of volunteer Seasearch divers they have been mapping seagrass beds and recording information about the wildlife that inhabits them.

They have gathered historical records of seagrass from numerous sources to compile an inventory of seagrass for the area. By learning about where seagrass exists and where it has been lost they are better able to understand and protect it. Download a copy of the Seagrass Inventory.


Studland Bay's Seahorses Future Uncertain!

There are a group of stakeholders who do not want Studland bay protected and wish to continue negative activities on on the site, damaging the seagrass and threatening the future of the Seahorses in the area.

Please help the seahorse trust and the MCS help protect these wonderful creatures by showing public opinion and voting on the Marine Conservation Societies Yours Sea Your Voice page.

Conservation Issues

Seagrass meadows are believed to be experiencing a world-wide decline, with global loss rates estimated at 2-5% year-1, compared to 0.5% year-1 for tropical forests. The causes for seagrass loss are multiple and include disease, extreme events, such as hurricanes and typhoons, burial by shifting sand, excess nutrient inputs to coastal waters and a reduction of water and sediment quality associated to eutrophication, and overgrowth by opportunistic algae, leading to seagrass loss, excess organic supply fromaquaculture and effluents, water quality deterioration by excess sediment inputs, mechanical damage from fishing activities, coastal engineering and boat activities; climatic extremes, such as heat waves and associated hypoxic events; displacement by invasive species, and excessive herbivory. Whereas actions are being taken to curb these trends, including legislation to protect seagrass meadows, transplanting efforts, and monitoring efforts to detect change, there is, as yet, no evidence that the associated recoveries compensate for the losses.

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