THE CORAL REEFS OF GOLFO-DULCE, COSTA-RICA - ECOLOGICAL ASPECTS

The coral reefs and coral communities in Golfo Dulce, southern Pacific Coast of Costa Rica, are described. The Inner Gulf reefs are characterized by a high topographic relief, low coral diversity and live coral covegage, and high dead coral coverage. The reefs can bc zoned into: 1. A reef-flat zone, where dead Pocillopora and Psammocora are predominant, together with live and dead microatolls of Porites lobata. 2. A reef-edge zone, where there is a marked change in physiognomy, from a relatively horizontal reef-flat to an almost vertical reef-front. This is the zone with highest live coral coverage and is for the most part Porites lobata. 3. A reef-front, extending from 2 to 10 m depth, made up mainly of dead Porites lobata. The Outer Gulf reefs are characterized by a low topographic relief, high live coral coverage and diversity, and low dead coral coverage. A total of nine scleractinian species were found in Golfo Dulce. Most abundant are Porites lobata, Psammocora stellata and Pocillopora damicornis, which have also been present there throughout the Holocene. Twenty four fish species were observed in two reefs. Most of them are important for the artesanal fisheries of Golfo Dulce. Other species are important reef herbivores or corallivores. Internal coral bioerosion (chiefly boring bivalves: Lihophaga) is more important than external bioerosion. Environmental conditions at Golfo Dulce were conducive to reef growth in the recent past but are now deteriorating as a result of increased sediment loads. Deforestation, pernicious agricultural practices and mining in the Golfo Dulce watershed must be brought under control and erosion reduced, lf these were possible a program of reef rehabilitation by transplanting corals could be started to recover some of the reefs.