There are more coral species around Puerto Rico than further north. There are many ‘coral’ species, that include 117 hard corals, 99 soft corals and gorgonians, 13 corallimorphs, 3 fire corals, and 5 hydrocorals making the Puerto Rico reefs the richest in the U.S. Caribbean. It is now clear that reefs surrounding the main island are degraded, because of nearby coastal developments, whereas the reefs near Descheo Island are probably the best- developed and healthiest in Puerto Rico, with about 70% coral cover and very clean water; however there are few long-term monitoring data available. The main branching elkhorn and staghorn corals (Acropora palmata and A. cervicornis) have declined in most places over the last 25 years due to hurricane damage, white-band disease, and coral-eating molluscs. Hurricane Georges heavily damaged A. palmata on the outer reefs in 1998 such that only one thicket remains between Margarita and San Cristobel. A. cervicornis has recovered considerably since Hurricane Georges and flourishes in shallow back-reef sites off San Cristobel, despite the presence of white-band disease. However, up to 10% of the A. palmata near La Paguera is affected by white-band disease and has not recovered, nor have the A. cervicornis around Mona Island recovered after Hurricane Georges. There are extensive seagrass beds in the shallow water around Puerto Rico and mangroves fringe the southern coast.

Fringing coral reefs with a total area of 3,370 km2 occur off the east, south and west coasts, around the 2 inhabited (Culebra and Vieques) and 3 uninhabited (Mona, Monito, Desecheo) small islands off Puerto Rico. Other areas of the shelf consist of hard ground and reef rock with scattered coral colonies and coral patches. The reefs have high hard coral diversity (125 species) along with 112 species of soft corals and gorgonians. The reefs have suffered major losses in coral cover through bleaching and disease, but stands of high coral cover (e.g. 70%) remain on some reefs which are remote from the land.

Modern shelf-edge reefs formed in Puerto Rico some 8,000 years ago (Adey, 1978). Inner reefs, formed on top of submerged banks and sandy bottoms of the flooded shelf are believed to be about 5,000 years old (Adey, 1978). The rise in sea level associated with the last Pleistocene glaciation (Wisconsin) flooded the lower limestone ridges of the shelf, providing appropriate sites for coral growth and subsequent reef development (Goenaga and Cintrón, 1979). Cross-shelf seismic profiles provided by Morelock et al. (1977) support the theory of Kaye (1959), which states that reefs on the southwest coast developed on drowned calcarenite cuestas formed as eolianite structures parallel to the coastline during the Wisconsin glacial period. Proper substrate, depth, and water transparency conditions in the southwest coast allowed for extensive development of coral reefs during the mid-Holocene period (Goenaga and Cintrón, 1979). At least three major types of reefs (rock reefs, hard ground reefs, coral reefs) are recognized within the Puertorrican shelf (García- Sais et al., 2003) although different coral reef formations have been reported (Goenaga and Cintrón, 1979; Hernández-Delgado, 1992; Morelock et al., 1977).

Rock reefs are submerged hard substrate features of moderate to high topographic relief with typically low to very low coral cover, mostly colonized by turf algae and other encrusting biota (Figure 5.2). Coral colonies are abundant in some cases (e.g., Diploria spp., Siderastrea spp., Montastrea cavernosa, Porites astreoides) but grow mostly as encrusting forms, providing minimal topographic relief. These types of reefs fringe the west and northwest coasts and are believed to be the main components of deep reef systems beyond the shelf-edge. Rock reefs are important habitats for fishes and macroinvertebrates since they are usually the only available structure providing underwater topographic relief in these areas. Some have developed atop of submerged rocky headlands and are characterized by the development of coralline communities adapted for growth under severe wave action and strong currents.

There are deep basaltic rock reefs; an extensive and complex system of slabs, boulders, crevices; and vertical walls associated with the insular slope. The most extensive deep reef formation is the great southern Puerto Rico fault zone (Glover, 1967; Garrison and Buell, 1971), a submerged section of the Antillean Ridge that extends across the entire Mona Passage. The ridge rises from a mean depth of 4,600 m and includes the islands of Mona, Monito and Desecheo, as well as submerged seamount peaks that rise to depths of less than 100 m, such as Bajo de Cico and Bajo Esponjas

Hard ground reefs are mostly flat platforms ranging in depth from 5-30 m and largely covered by turf algae, encrusting sponges, and scattered patches of stony corals (Figure 5.2). Coral colonies are typically encrusting forms, an adaptation to the extremely high wave energy that prevails seasonally on the north coast. Many of the encrusting coral colonies grow over vertical walls in crevices among the hard ground. The barrel sponge, Xestospongia muta, is usually abundant in hard ground reefs, where it represents one of the main features contributing topographic relief. Low-relief sand channels aligned perpendicular to the coast cut through the hard ground platform in many areas and provide topographic discontinuities. The sand is generally coarse and mostly devoid of biota, reflecting short deposition times and highly dynamic movements across the shelf due to the high wave action. These systems are found off the north central and northeast coastlines (García- Sais et al., 2003).

Coral reefs are mostly found as fringing, patch, and shelf-edge formations in Puerto Rico. Fringing coral reefs are by far the most common. These are located throughout most of the northeast, east, and southwestern coastlines associated with erosional "rocky" features of the shelf. In most instances, coral is not the main constituent of the basic reef structure, but its development has significantly contributed to topographic relief, influencing the sedimentation of adjacent areas and providing habitat for a taxonomically diverse community that is consistent with a coral reef system (García-Sais et al., 2003). On the south coast, coral reefs fringe many small islands or keys, and are found as extensive coral formations associated with the shoreline at the mouths of coastal embayments. In some instances, coral growth has been primarily responsible for the formation of emergent island reefs, or keys, such as the reefs off La Parguera (García-Sais and Sabater, 2004). Fringing reefs are also found off the northeast coast, mostly on the leeward section of the islets off Fajardo (in the Cordillera de Fajardo Natural Reserve).

Shelf-edge reefs are the best developed (but least studied) coral reef systems in Puerto Rico. An extensive reef formation is found at the shelf-edge off the southwest coast in La Parguera. This reef displays the typical "spur-and-groove" growth formation with sand channels cutting through the shelf perpendicular to the coastline (Figure 5.2). Also, the reef formations at the shelf-edge of Ponce (Derrumbadero), Guánica, and Desecheo and Mona Islands are characterized by structurally and taxonomically complex communities. The shelf break on the north coast is characterized by a more gentle slope than on the south coast and the substrate is generally sandy or a flat, hard ground with low relief. Scattered rock reefs occur throughout many sections of the north coast. Some are present down the insular slope and represent the main substrate for deep reef communities with live hermatypic and ahermatypic corals providing important physical habitat.

The Coral Reef Monitoring Program for Puerto Rico, which is sponsored by the National Oceanic and Atmospheric Administration (NOAA) and administered by the Puerto Rico Department of Natural and Environmental Resources (DNER), is now fully implemented and has achieved its initial goals in collaboration with Federal and local governmental agencies and marine scientists from research institutions.

Puertorrican coral reefs were initially described in terms of their taxonomic composition by Almy and Carrión-Torres (1963). This initial survey identified a total of 35 species of scleractinian corals from La Parguera, on the southwest coast of Puerto Rico. Later surveys were reported by Rogers et al. (1978), Armstrong (1980), Goenaga and Boulon (1991), Hernandez-Delgado (1992, 1994a,b), and Hernandez-Delgado and Alicea- Rodriguez (1993a,b).

Goenaga and Cintrón (1979) prepared the first geographical inventory of Puertorrican reefs. This work, along with subsequent qualitative surveys of reef geomorphology and community structure (Cintrón et al., 1975; Canals and Ferrer, 1980; Canals et al., 1983), established criteria for designation of marine areas with coral reef development as natural reserves by the government of Puerto Rico.

Puerto Rico: The Commonwealth of Puerto Rico comprises the main island of Puerto Rico plus Culebra, Vieques, Monito, and Desecheo offshore islands in the northern Caribbean. Surrounding the islands and cays are a complex mosaic of coral reefs, seagrass beds and mangrove forests. There are also deep coral formations, including the ‘Deep Terrace’, ‘Drop-off Wall’ and ‘Rhodolith’ reefs down to 90 m depth. These are critical habitats for fish and invertebrates.

Deep Hermatytpic Coral Formations (Mesophotic reefs)



Deep hermatypic coral formations recently described in Puerto Rico include the "Deep Terrace", "Drop-off Wall" and "Rhodolith" reefs, which contain nodules of unattached, branching, coralline algae. "Deep Terrace" reefs have been found at depths between 30-90 meters growing over flat or gently sloping terraces in very clear water. The dominant coral species is a flattened plate morphotype of Montastraea annularis complex; lettuce corals (Agaricia lamarki, A. grahame) and Porites astreoides are also common. García-Sais et al. (2004) described one of these reefs, locally known as Black Jack, off the south coast of Isla de Vieques (Figure 3.2). The reef is similar to those reported by Nemeth et al. (2004), and Armstrong et al. (2006) within the Marine Conservation District off the south coast of St. Thomas, U.S. Virgin Islands (USVI), a known spawning aggregation site for red hind (Epinephelus guttatus; Nemeth et al., 2005). Similar reef formations may be present off the east and south coasts of Vieques, north-east coast of Culebra, and on deep terraces of the outer insular shelf of the USVI. Some of these reefs are important spawning aggregation sites for groupers. El Seco, an undescribed deep terrace reef formation located off the east coast of Vieques is a known spawning aggregation site for tiger grouper (Mycteroperca tigris; Sadovy et al., 1994).



A total of 25 species of scleractinian corals, two antipatharians and one hydrocoral were identified during the snapshot survey of Black Jack Reef by García-Sais et al. (2004). Live coral cover averaged 28.8% (range 25.0-40.4%) within videotransect areas. The Montastraea annularis complex was the dominant coral species in terms of substrate cover (mean: 21.9%), representing 76% of the total live coral cover at depths between 36-40 m., and generally exhibited laminar or flattened growth with closely spaced colonies of moderate size and low relief. Corals grow mostly from a pedestal of unknown origin, creating protective habitat underneath the coral. The laminar growth pattern appears to be an adaptation for optimum light utilization. Other coral species that presented substrate cover above 1% and that were present in at least four out of five transects surveyed include Porites astreoides, Agaricia grahamae and M. cavernosa. One large colony of the bushy black coral (Antipathes caribbeana) was present at the deep terrace of Black Jack Reef. Turf algae was the dominant biological assemblage in terms of reef substrate cover with 57.4 %. Fleshy (Lobophora variegata) and calcareous algae (Halimeda sp.) were also present within transect areas. The combined mean reef substrate cover by benthic algae within transect areas surveyed was 64.2% (García-Sais et al., 2004).An extensive Deep Terrace reef formation associated with the submerged seamount at Bajo de Sico (Mona Passage) has been recently described (García-Sais et al., unpub. data). The reef extends across the entire northwest section of the seamount at depths between 45 and 90 meters over a relatively flat, gently sloping, hard bottom terrace. Biological characterization and benthic habitat mapping efforts of this reef system are ongoing at present as part of a project sponsored by the CFMC and NOAA, with the support of NOAA’s Center for Coastal Monitoring and Assessment Biogeography Branch (CCMA-BB).



A total of 54 reef fishes were identified from Black Jack Reef, 33 of which were present within three (3 x 10 m) belttransects surveyed between 10:00-12:00 AM (García-Sais et al., 2004). The mean abundance of fishes was 549.3 individuals/30 m² and the mean number of species per transect was 16. An assemblage of three species represented 95% of the total fish abundance within belt-transects. The numerically dominant species was the masked goby (Coryphopterus personatus) with a mean abundance of 390 individuals/30 m². This is the highest density ever reported for a demersal fish within a belt-transect from a reef surveyed in Puerto Rico. Following in abundance were the Creole wrasse (Clepticus parrae) with 93.0 individuals/30 m² and the blue chromis (Chromis cyanea) with 36.7 individuals/30 m².

Johnston Atoll

Drop-off Wall Reefs



Deep hermatypic reefs have developed on drop-off walls at the upper slope of oceanic islands, such as Isla Desecheo (García-Sais et al., 2005b), and on the reef top and upper slope of the seamount at Bajo de Sico in Mona Passage (García-Sais et al., in review). The Southwest Wall reef of Isla Desecheo is found at depths between 30-40 m and is dominated by benthic macroalgae (mostly Lobophora variegata), sand, sponges and massive scleractinian corals (García-Sais et al., 2005b). Sponges are highly prominent (mean surface cover: 17.3%), growing mostly as large erect and branching forms that provide substantial topographic relief and protective habitat for fishes and invertebrates. In many instances, sponges grow attached to stony corals forming sponge-coral bioherms of considerable size. One of the most common associations consists of brown tube (Agelas conifera, A. sceptrum) and row pore sponges (Aplysina spp.) with star corals (Montastraea cavernosa, M. annularis). A total of 25 scleractinian corals, three hydrocorals and two antipatharian (black coral) species were identified from the Southwest Wall Reef at Isla Desecheo. Great star corals (M. cavernosa, M. annularis complex) were the dominant species of scleractinian corals at the site (García-Sais et al., 2005b).



A total of 70 fish species were identified from depths below 30 m at southwest Wall reef (García-Sais et al., 2005b). The numerically dominant ichthyofauna within belt-transects surveyed was comprised by zooplanktivorous taxa, suggesting that planktonic food webs are most relevant on deep hermatypic reefs. Drop-off wall reefs studied at Isla Desecheo are the natural habitats of many exploited commercially important food fishes, such as large groupers (Epinephelus striatus, E. guttatus, Mycteroperca venenosa) and snappers (Lutjanus spp.), and target species of the aquarium trade (Chromis cyanea, Gramma loreto, Centropyge argi, Chaetodon spp., Opistognathus spp.). Densities of adult red hind (E. guttatus) from 40 m at the southwest Wall are the highest reported for Puerto Rico (García-Sais et al., 2005b).

Rhodolith Reefs



Rhodolith reefs have developed along gently sloping terraces below depths of 40 m at Isla Desecheo and Bajo de Sico. Agelas Reef is a crustose algal rhodolith formation colonized by encrusting brown algae (Lobophora variegata), large erect and branching sponges (Agelas spp., Aplysina spp.) and lettuce corals (Agaricia spp) found at depths of 40-70 m in Isla Desecheo (García-Sais et al., 2005b; Figure 3.2). The sessile-benthic biota, including corals, grows attached to a vast deposit of rhodolite nodules that are loosely anchored to the bottom. Reef substrate cover by live biota is over 95%. Agelas Reef has very low topographic relief and massive corals do not contribute significantly to its rugosity. A total of 18 species of scleractinian corals, two hydrozoans (Millepora alcicornis and Stylaster roseus) and the antipatharian black wire coral (Stichopathes lutkeni) have been reported from Agelas Reef (García-Sais et al., 2005b). The combined mean substrate cover by the nine species of scleractinian corals present within video-transects at Agelas Reef was 13.1% (range: 7.4-36.4%). Irregular sheets or laminar growth by lettuce corals prevailed at depths between 45 and 53 meters, with a combined reef substrate cover of 8.9%, representing 70% of the total cover by scleractinian corals. Lamark’s sheet coral (Agaricia lamarki) and Graham’s sheet coral (A. grahamae) were the main coral species present within transects surveyed (García-Sais et al., 2005b).