Anyone driving along the Western Main Road, near Dhein's Bay, during a downpour, can see the river of red earth flowing down the hillside, across the road and into the sea.

What they do not see is the effect that runoff has on the coastal environment into which it flows and is deposited.

Rain washes soil from slopes which have been bared by bush fires, logging and construction.

Such runoff substantially increases the amount of sand, silt and clay entering coastal waters. Sediment smothers sea grasses, reducing their food-making potential and making recovery impossible in some cases.

The loss of sea grass communities in the Gulf of Paria will only accelerate already declining fishery resources.

Sea grass beds are among the ocean's ore productive ecosystems. Most of us have encountered sea grasses on our outings to the beach - those "slimy weeds" which our feet meet when we expect to feel smooth sand beneath inviting water. Commonly referred to as "seaweed" in Trinidad and Tobago, sea grasses are actually distinct from seaweed or algae, and like their relatives, the land grasses, they develop flowers, fruit and seeds.

They form the only group of submerged flowering plants in the sea and thrive in many shallow-water coastal habitats. Together with algae they can form very extensive beds. The most commonly found sea grass species in Trinidad and Tobago is called turtle grass.

In Trinidad, extensive sea grass beds are found on the west coast, at William's Bay in Chaguaramas extending straight down to St Peter's Bay in Carenage and near to the Point Cumana River.

Smaller communities are found near the Trinidad and Tobago Yacht Club and the Pointe-a-Pierre Yacht Club. Recently, sea grass has been found in North Claxton Bay and in Sea Lots. On the east coast, sea grass beds can be found in Salybia and in north Guayaguayare Bay.

In Tobago, extensive sea grass communities are found in Bon Accord Lagoon, Kilgwyn Bay and Petit Trou Lagoon. These sea grass communities are closely associated with coral reefs and mangrove swamps. Smaller patchy communities are found in other areas.

Why are sea grass communities important to our environment and why should we preserve these natural resources? Because they have a number of important functions. Many of our popular fish and shellfish spend at least part of their lives in sea grass beds. These include immature snappers, croakers, grunts, groupers and others.

Sea grasses are also home to lobsters, serrette crabs, queen conchs, shrimp and such fascinating species as sea urchins, sea cucumbers, starfishes, and an array of snails, anemones and sponges.

Juvenile reef fish such as goatfish, hogfish, parrotfish, butterfly fish, doctor fish and even seahorses, can be found in the sea grass beds in Bon Accord Lagoon.

Turtles such as the hawksbill and green turtle graze on sea grasses, hence the name "turtle grass".

The diversity and abundance of marine species in sea grass beds are quite high, and although they do not provide the spectacle which coral reefs do, or the grandeur of a fine stand of mangroves, they can provide hours of interest to the intrepid snorkeller.

Sea grass beds are also major food manufacturers in the coastal environment.

Like land grasses, sea grasses absorb carbon dioxide and minerals from the environment, and using energy from sunlight convert them to organic material. This organic material is food for many marine species.

The sea grass blades also provide surfaces for algal growth; algae being an important food source for many fishes. Consequently, the high productivity rate of this system is linked with high yields in associated fisheries.

When the sea grasses die, they form detritus and release minerals back to the environment, making it available for other organisms.

Sea grasses are therefore nutrient sinks and sources and they help in nutrient recycling.

Paradoxically, their greatest contribution to the chain of life is death.

Sea grasses are coastal stabilizers as they provide protection against coastal erosion. The sea grass blade slows and retards current flow, reducing overall water flow. The roots and rhizomes of the grass form a complex, interlocking matrix, which binds the sediment and retards erosion.

In spite of their great importance however, sea grass beds are disappearing. Those once found in Scotland Bay, in Grand Fond Bay (Monos Island), Five Islands, Cocorite and Speyside in Tobago have already disappeared.

Many of the sea grass communities described are being threatened by coastal development. Beds in La Guira Bay were damaged when dredge material was dumped there during the Crown Point Airport extension.

In Bon Accord Lagoon, the extensive sea grass community is threatened by proposed hotel development and is constantly stressed by the release of excessive organic material (mainly sewage), and physical damage caused by boat anchors and propellers.

The numerous bush fires, which took their toll on land during the dry season, continue to take their toll on coastal vegetation during the rainy season, as unprotected soil runs off the land and into the sea, smothering these coastal systems.

Unless we understand the importance of sea grass beds and act to ensure that they are not subjected to such abuse, they will continue to disappear at an alarming rate.

Their loss will further diminish our marine environment and the animals for which they provide nurseries, shelters, and feeding places will also suffer and disappear.

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