Spatial distribution of epibenthic bryozoans found on the roots of Rhizophora mangle, Kingston Harbour, Jamaica, W.I.

The abundance and distribution of the bryozoan species on the prop roots of the red mangrove, Rhizophora mangle, at diverse locations around Kingston Harbour is described. The study was carried out in four mangrove areas (Port Royal, Great Salt Pond, Dawkins Pond and Hunts Bay) over a 15 mo period between September 1994 – December 1995 and included a total of 12 stations. Five roots from each sample station were collected each month and analyzed. Water depth, root density, root length, transparency, dissolved oxygen, temperature, suspended solids, and salinity were measured for each station. The estimate of abundance of the bryozoan species and other sessile invertebrates was carried out using a modified point intercept method in which a template of transparent Perspex with 100 points arranged in a 5 × 20 grid was placed over the roots. Twelve categories (Bryozoa, Hydrozoa, Amphipoda, Cirripedia, Porifera, Ascidiacea, Bivalvia, Anthozoa, Polychaeta, Algae, Other and Bare Root) were selected for classification of the sessile community. Of the environmental parameters measured, salinity showed the expected pattern with greatest variability and lowest mean values (24.0–24.2) in Hunts Bay. A diverse assemblage of organisms with a total of 86 species colonized the submerged portions of the mangrove prop roots. Dawkins Pond and Hunts Bay had fewer taxonomic groups. Bryozoan species were found at all stations with relative abundances ranging from 2–70%. The bryozoan species were, however, not well represented in the sessile community of the Great Salt Pond while they dominated that of Hunts Bay. There were a total of 18 bryozoan species identified. In Port Royal, which contained the most extensive red mangrove stands, a total of 17 species were discovered. This compared to eight species found in the Great Salt Pond and three species each in Dawkins Pond and Hunts Bay. The species composition found in the Great Salt Pond was similar to that found in Port Royal while Dawkins Pond and Hunts Bay had fewer species including a new undescribed species of Bowerbankia. The salinity levels, although a contributing factor, do not fully explain all the differences observed in the composition of the communities. The history of the community probably played an important role in the variability observed with the added interaction of such factors as seasonal growth, predation, physical disturbances, larval dispersal and recruitment.