SHALLOW VERSUS DEEP BRYOZOAN ASSEMBLAGES ON EASTERN SAMBO REEF IN THE LOWER FLORIDA KEYS -- DATA FOR PALEOECOLOGIC COMPARISONS

Near the southwestern end of the Florida Keys, Eastern Sambo (at 24º 29.7' N, 81º 39.7' W) is one of the small reefs which make up the outer reef tract in that area. Sampling bryozoans in different parts of this reef adds knowledge of species distribution in this important modern reef region, and also furnishes comparative data for analyzing bryozoan contributions to fossil reefs like those in the Pleistocene near-by as well as in geologically earlier ones such as the Permian of the southwestern United States.

     The bryozoans here are cheilostomes (with one exception), underneath coral rubble, thus playing the accessory cryptic or coelobitic, hidden-encruster constructional role here. Bryozoan diversity is relatively high (22 species identified from 110 colonies), but depth differences are apparent and likely would be detectable in fossilized counterparts.

     The most common species in the Eastern Sambo shallows (0-10 m depth) are Cleidochasma porcellana*, Hippopodina feegeensis, Steginoporella magnilabris, and Stylopoma spongites*; (* indicates species which also occur rarely in the other part of this reef). In the deeps (20-30 m), Trematooecia turrita* and Reptadeonella violacea are most common.

     Additional rare species help further differentiate the depth zones on this reef. Celleporaria albirostris, Membrendoecium parvicapitatum, and the cyclostome Lichenopora radiata characterize the shallow zone. The deep zone is distinguished by Antropora granulifera, Cellepora? coronata, Crepidacantha poisonii, Cribrilaria radiata, Floridinella typica, Parasmittina signata, Smittina delicatula, S. smittiella, and Stenopsella fenestrata.

     Finally, several more species occur rarely in both shallow and deep zones here, and hence are not diagnostic of either: Crassimarginatella crassimarginata, Holoporella hemispherica, Parasmittina spathulata, and Rhynchozoon vaughani.