Examples of the following habitats may often be included incidentally in MPAs. However, if reefs are to flourish, they should be deliberately identified and protected within MPA boundaries.

• Reef flats. Corals on reef flats and upper reef crests that are exposed at low tides often exhibit stress tolerance and may resist or recover rapidly from bleaching. They will be important providers of larvae that may settle in dead areas and aid their recovery.

• These reef flats often provide vital nurseries for reef fishes that will move onto the reef and help reestablish communities affected by bleaching.

• Nitrogen and organic material produced on the reef flats, or transported from there in the form of feces of herbivorous fishes and other organisms, all contribute valuable nutrients to the reef community and aid in its functioning and recovery.

• Back-reef lagoons. Coral assemblages in back-reef lagoons, especially shallow lagoons behind fringing reefs, are routinely exposed to wide temperature fluctuations (the ponding effect) and consequently may exhibit some acclimatization to temperature stress and resistance to bleaching.

• Back-reef lagoons are also important nurseries for fishes.

• Corals in naturally turbid, deeper lagoons may show higher resistance to bleaching than corals of the same species in clear waters over barrier reefs.

• Seagrass beds and sand flats. Seagrass beds and sand flats surrounding coral reefs are important feeding grounds for nocturnal feeding fishes, such as snappers and grunts, which shelter on reefs by day. When they return to the reef, these fishes deposit nutrients in the form of feces that are introduced to the reef food web and contribute to the growth and recovery of reef communities.

• Mangroves. The generally turbid waters and shading effect of mangroves may reduce the susceptibility of corals in that area to bleaching.

• Mangroves also provide nurseries for juveniles of certain reef fishes (e.g., groupers, parrotfishes, and snappers)

• Where they are close enough to reefs, mangroves provide feeding grounds to fishes that shelter on the reefs.

• Mangroves introduce fixed nitrogen and organic detritus into the food chain of reefs, as do reef flats and seagrass beds.

• Beaches and dunes. Coastlines are dynamic zones. Disturbances to them may cause beach erosion and alteration of the natural cycle of accumulation and erosion of sand along the shore, increase turbidity of inshore waters, or even smother living reefs with excessive sediment.

• This is especially true of sand cays, which have been known to move across reefs, fall off into deeper water and disappear for good, as occurred at Maziwi Island, Tanzania. Before its disappearance, Maziwi Island was the most important green sea turtle nesting beach off mainland Tanzania.