CONOCIENDO EL TERRITORIO

Yet another important aspect of vulnerabi 1 iH^y^ to oil pollution which has to be taken into accoount, is the biological aspect i.e. the impact of oil on the living

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resources iri the marine environment.

The Norwegian Nature Conservation Act defines the basic goal for a pollution control policy as the maintenance of quality and biological productivity of nature. This is particularly applicable, to the marine environment, where

life generally depends on the maintenance of ecosystems in

balance. . .

Some of the most important ecosystems in the tropical region may be found in mangrove swamps. The impor­ tance to the marine environment of the mangrove swamp, can­ not be overemphasized.. They provide nurseries and feeding

grounds for commercially important species of fish and crustaceans. Their roots and lower trunks support a variety of crabs, oysters, barnacles and other invertebrates. Mangroves protect shorelines and river banks from erosion and generally assist in land reclamation. They offer protec­

tion from siltation to coral reefs, which may be generally found growing beyond the mangroves. The area of the mangrove swamp is richer in nutrients than the land or sea around them and this contributes to their fertility.

To date, very little scientific research has been conducted to assess the effects of oil on mangroves. It has been observed, however, that in the short term there is

likely to be high mortalities of turtles, invertebrates and fish in the event of a spill. In the longer term i.e. over 5 years, the oil may weather comparatively quickly and recolo­ nisation of both mangrove and invertebrates has been

observed. (4) In cases of chronic pollution, it has been found that mangrove? are irreparably destroyed. .

The treatment of oil in mangrove swamps is also difficult due to the type of soil found there. The nature of the mangroves automatically rules out the use of dispersants and/or manual methods of collection. The use of dispersants, even those which are very slighlty toxic, may cause great harm to-the communities of marine life within the swamp. It can also smother the breathing pores of the mangroves them­ selves, causing widespread death among trees. Manual collection, because of the tangle of roots, the mud, etc. may cause more destruction than solve the problem. In other words, with these systems prevention is better than cure.

Both Trinidad and Tobago possess extensive areas of mangroves. In Trinidad, the Caroni Swamp has the biggest acreage, but there are also important areas in the Oropouche and Nariva/Mayaro Swamps. During the last decade or so, the productivity of the Caroni Swamp has been affected by certain practices which have led to increased pollution, often by oil. The effect of continuous spillage in these areas, as well as preventive measures which may be employed, need to be investigated and utilised.

In Tobago, the mangrove complex at the south western point of the island, provides protection for the Buccoo Reef - the island's most extensive reef system. The Bon Accord lagoon, as it is known, is representative of an oceanic*mangrove community with predominant vegetation being the red mangrove. The roots act as suitable substrate for oysters, sponges, algae and corals. Among the roots are found conch, crabs, shrimps, snails and other micro­ organisms. The aerial parts of the mangrove provide good roosting for sea and land birds. The entire lagoon serves as

a nursery for several species of commercial and sport fish, by providing the juveniles with food, cover and protection. The lagoon is crucial to the maintenance of the physical stability and productivity of the land/sea interface, inclusive of the reef.

Other resources which are also at risk, if the marine environment becomes polluted by oil include the wild

life sanctuaries situated on off shore islands, such as Soldado Rock, St. Giles Islands and Little Tobago. The St. Giles Islands supports one of the most important sea bird breeding colonies, in the southern Caribbean, especially with reference to the larger species of birds, such as the Magnificent Frigate bird and the Red-footed Booby. Except for Soldado Rock, which lies almost in the middle of the off shore marine fields in the Gulf of Paria, the greatest threat to these sanctuaries would be from an incident of accidental pollution - either a tanker collision or a well blowout. In the case of the Soldado Rock sanctuary, the effect, if any, of- chronic pollution on the inhabitants of the Rock would have to be evaluated, in any calculations of the island's vulnerability.