Discussion

The southwest part of Puerto Rico, reaching from Añasco to Ponce, has three broad carbonate platforms and two areas of very narrow shelf. The three platforms - Boquerón, La Parguera and Peñuelas - have very little river sediment influx and the bottom sediments are calcareous. The shelf at Añasco-Mayagüez has three river discharges and the Guánica-Guayanilla-west Ponce shelf also has river discharge; they have large terrigenous sediment facies with common resuspension of fine grained terrigenous sediments.

High sediment influx, resuspension and turbid water conditions at Añasco-Mayagüez and Guánica-Guayanilla-West Ponce have resulted in low coral cover on the reefs (Figure 83) . At the surveyed sites, the bottom is hard dead coral rock which indicates that these once had cover comparable to that on the platforms of Boquerón, La Parguera and Peñuelas. It is therefore a reasonable assumption that much of the insular shelf and slope of southwest Puerto Rico has turned from coral reef to "hard ground" condition with a loss of more than 35 percent of the original Modern coral cover. This is especially evident if we compare the total cover by species at the 20 m level for sites (see figure 55) discussed in this paper. The La Parguera and Peñuelas platforms are the only areas of "normal" coral cover at 20 m. The western platform insular slope has low coral cover due to some natural process. The Añasco-Mayagüez and Guayanilla-west Ponce reefs have very low total coral cover at 20 m compared to the La Parguera and Penuelas reefs at this depth (Figure 84) . The shelf edge reef at Guánica still has a moderate cover of living coral at 20 m.

Individual reefs on the carbonate platforms show loss of coral cover by areas of dead coral rock. Continued rapid urbanization and development has contributed to sheet runoff and influx of terrigenous sediments even into areas without river discharge. The development of the coastal area has also increased discharge from the sewer outfalls at Ponce, La Parguera, Boquerón and Añasco. This untreated sewage has raised nutrient levels and promoted the growth of algae on the reef.

And finally, overfishing and drastic reduction of the biodiversity around the reefs is leading to rapid loss of coral to a shift in competition balance favoring algae and destroyers of coral such as corallavore, fire worms, echinodermatra and damsel fish. Along with this we are finding increased coral disease and invasion by sponge.

Specific members of the reef-building coral community have suffered higher loss under present conditions. The two major reef building species - Acropora palmata and Montastraea annularis have been drastically reduced in percent of cover on the stressed reefs. At depths greater than 12 to 15 meters, dead coral is all that remains of reefs that must have once had a cover comparable to the magnificant shelf edge reefs at La Parguera.