BULLETIN FLORIDA STATE MUSEUM


0. "







FIGURE 5.-Typical fringing reef:, lagoon, and sand-coral beach, Grand Cayman.

 A distinctive feature of Grand Cayman is its immense North Sound
(Fig. 1), embracing some 64 km2 and partially separated from the open
sea to the north by a broken reef and shoals. The greatest depth of the
sound (near its center) is only about 6 m; much of its shallow floor
abounds in turtle grass (Thalassia testudinum). Although the boundary
of the North Sound with land is not always clear-cut, nonetheless much
of its periphery is composed of red mangroves (Rhizophora mangle),
with occasional mangrove islands in the sound. The sound and its fring-
ing red mangroves are not generally used by aquatic birds, but at least
one island (Booby Cay) is a well-known heron rookery, whereas other
small mangrove islands provide temporary roosting sites for frigate birds,
herons, and egrets.
 SAND-CORAL BEACH.-The coastlines of the islands are composed of
coral cobbles, sandy beaches, or steep bluffs. The beaches are best de-
veloped for about 5 km on the western end of Grand Cayman, a popular
resort area. Steep bluffs (6-30 m) dropping off into deep water are best
developed along the northeast coast of Grand Cayman and at the eastern
end of Cayman Brac.
 The sand-coral beach formation (Fig. 5) consists of blown coral sand
and well-rounded coral fragments piled up and worn by winds, waves,
storms, and hurricanes. This formation, some 3-10 m wide, has little
covering vegetation, but some pioneer plants grow on it including


Vol. 19, No. 5