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Marine biological investigations in the bahamas 22. Litioral zonation at three Bahamian beachrock localities

1992; Taylor & Francis; Volume: 77; Issue: 2 Linguagem: Inglês

10.1080/00364827.1992.10413495

1503-1128

Hans Brattström,

Marine Biology and Ecology Research

Abstract The three localites are described and the vertical distribution of the species found is illustrated in diagrams. The stations were slightly sloping and fairly sheltered because wide and shallow reef flats off the shore acted as breakwater. The outer part of the shore consisted of rocks and slabs, the inner of sand. The lowest rocks belonged to the yellow zone, the upper to the black, the limit between the zones being found at a height of 60–75 cm. The upper limit of the black zone varied more depending on where the sand began. A division of the yellow zone into two subzones as known from Florida and the Bimini Islands, was more or less distinct. Lowest down the rocks were covered with a felt of small, sand-encrusted algae, in which felt also larger algae occurred. Except farthest out few animals were seen on the surface of the rocks. Those present there were mainly found in crevices and under overhangs, and distinct horizontal belts were seldom developed. Most animals lived hidden. Lowest down boring organisms were common, and under the rocks and slabs was a system of water-filled or moist cavities with a teeming animal life higher up and farther in than would have been possible otherwise. Many of these hidden animals had either lower or upper limits in common, resulting in a zonation pattern. A comparison is made with some earlier described localities in the Bimini Islands and the Florida Keys. These localities were topographically different from the beachrock stations described in this paper. In spite of this the fauna composition and levels of occurrence were fairly similar at all localities, a similarity which was closer at the highest level. The greatest difference was the lack at Bimini and in Florida of the system of cavities below the rocks, which was typical of the stations described in this paper, and accordingly the lack of the organisms living in such cavities.