Alternate Title

A Note on the Distribution of Some Sponges and Corals in a Seagrass Bed, Long Key, Florida


The ecology of sponges and corals in Florida reefs and on other hard bottoms has received attention in the literature, but in some tropical environments, such as seagrass beds, these organisms are less well known. Surveys reported here provide quantitative baseline estimates of the densities and distributions of some of the common sponges (Tedania ignis, Chondrilla sp., Chalinula sp.) and corals (Manicina areolata, Porites sp., Cladocora arbuscula). A seagrass bed dominated by turtle grass, Thalassia testudinum, directly off the eastern coast of Long Key State Park in the Florida Keys was monitored. The numbers of corals and sponges were recorded by snorkelers using 3X3 m random individual quadrats or quadrats in a continuous tract. Seagrass density was recorded on an ordinal scale. Of the organisms examined, only Manicina sp. numbers showed a significant, although negative, correlation with seagrass; weak positive relationships between the numbers of Chondrilla sp. and Chalinula sp. sponges and between the C. arbuscula and Porites sp. corals were observed. Based on a comparison of the observed numbers with those in Poisson and negative binomial distribution models, all six species that appear have aggregated distributions. The degree of clumping was also quantified using several mathematical indices and was in general agreement with the Poisson probabilities, although when Morista’s index is calculated, M. areolata clumping resulted in what is probably a high estimate. The data from the continuous grids were used to estimate the size and discreteness of the clumps; the species that had shown positive correlations had radii that were very similar.