coral reefs pps164 165
Location Community Description A coral reef is a hardened substrate of mounded relief formed by the deposi- tion of calcium carbonate by reef-build- ing corals and other organisms, relict or ongoing. This category includes the reef crest, back reef, and fore reef areas. The reef crest is the shallow and often emergent portion of the reef, usually colo- nized by fire coral (Millepora spp.) and other wave-resistant invertebrates and emer- gent coral. It is a high-energy wave area often visible in aerial images. The back reef is that portion of the reef that is landward of the reef crest. Behind the back reef, shallow lagoons may form, creat- ing a protected area. In some cases, the back reef slope to the bottom of the back reef lagoon is steep and composed of large interlocking pieces of dead elkhorn coral (Acropora palmata), which provide good shelter for the many species of fish found here. The floor of the lagoon is usually sand and may be colonized with patches of sea- grass, algae, and the upside-down jellyfish, Cassiopeia frondosa. …
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Location Community Description A coral reef is a hardened substrate of mounded relief formed by the deposi- tion of calcium carbonate by reef-build- ing corals and other organisms, relict or ongoing. This category includes the reef crest, back reef, and fore reef areas. The reef crest is the shallow and often emergent portion of the reef, usually colo- nized by fire coral (Millepora spp.) and other wave-resistant invertebrates and emer- gent coral. It is a high-energy wave area often visible in aerial images. The back reef is that portion of the reef that is landward of the reef crest. Behind the back reef, shallow lagoons may form, creat- ing a protected area. In some cases, the back reef slope to the bottom of the back reef lagoon is steep and composed of large interlocking pieces of dead elkhorn coral (Acropora palmata), which provide good shelter for the many species of fish found here. The floor of the lagoon is usually sand and may be colonized with patches of sea- grass, algae, and the upside-down jellyfish, Cassiopeia frondosa. The upper fore reef habitat is some- times found near shore, usually in the seaward shallow portions of fringing or barrier-type reefs from the reef crest to approximately 3 meters (10 feet) in depth. It is comprised of highly branching elkhorn coral (A. palmata), but other species may be present, including finger coral (P. porites), mustard hill coral (P. astreoides), lettuce coral (A. agaricites), brain coral (Diploria sp.), and fire coral (Millepora sp.) The predominance of elkhorn coral pro- duces a structurally complex habitat with good capacity to act as refuge and shelter. As a result of this complexity, this habitat serves as a principal daytime refuge for many species of fish that forage away from the reef at night in the adjacent seagrass beds and pavement areas (e.g., grunts and snappers). It may also be used at night by many species that rest here, hidden in the many crevices and caves. CORAL REEFS: fringing, bank, barrier and linear reefs Good Examples: St. Croix––Buck Island, Turner Hole, Jack and Isaac Bays, Lang Bank. St. Thomas––Saba and Flat Cays, Great Hans Lollick, Cow and Calf. St. John––Newfound Bay, Hawksnest Bay, Waterlemon Cay. Elkhorn coral grows at the reef crest. Staghorn coral Finger coral Mustard hill coral Brain coral 165 164