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Estimating Surface Area of Sponges and Marine Gorgonians as Indicators of Habitat Availability on Caribbean Coral Reefs
Citation:
SANTAVY, D. L., L. A. COURTNEY, W. S. FISHER, R. L. QUARLES, AND STEVE J. JORDAN. Estimating Surface Area of Sponges and Marine Gorgonians as Indicators of Habitat Availability on Caribbean Coral Reefs. Hydrobiological Journal. Begell House Incorporated, New York, NY, 707:1-16, (2013).
Impact/Purpose:
The goal was to develop a field method to determine SA of the dominant marine gorgonian and sponge morphologies in the shallow water reefs of the Central Western Atlantic Ocean. An approach was sought that could be applied rapidly and effectively by non-specialists with limited resources. Because the objective was to estimate SA generated by taxa with complex morphologies, a morphological, rather than a taxonomic approach was used to classify organisms and generate simulated composite images. It is known that in the same species of sponges and some octocorals, a high level of morphological plasticity can occur (West et al. 1993; Kaandorp 1999; Kim et al. 2004), so taxonomic classification is inappropriate. Regression models and geometric surrogates were developed to determine the best models to estimate SA for different morphological classes based on measurements of height and diameter in the field. To our knowledge, this is the first application of three dimensional computer modeling to classify and analyze gorgonian and sponge morphologies.
Description:
Surface area and topographical complexity are fundamental attributes of shallow tropical coral reefs and can be used to estimate habitat for fish and invertebrates. This study presents empirical methods for estimating surface area provided by sponges and gorgonians in the Central Western Atlantic Ocean using only colony height, diameter and morphology. Application of these methods can augment surface area estimates of scleractinian corals in field studies. Computer simulated colony images with known surface areas were developed for different morphological classes of sponges and of gorgonians. Images were generated from morphometric data compiled from existing taxonomic descriptions in the literature and from field data collected at reefs in southeastern Florida and southern Puerto Rico. Three-dimensional modeling software was used to determine the actual surface area of each simulated image. Stepwise regression analysis was used to generate models for estimating colony surface area using height and diameter as variables. Regression models and geometric surrogates were examined for similarity to a composite mean of simulated images for each morphology type using covariate analyses. Results indicated that the best estimates were generated by regression models, which exhibited forecast errors less than 20%. Using these models, colony height, diameter and morphology can be used to estimate surface area contributions of gorgonians and sponges to evaluate habitat availability for fish and invertebrate assemblages on shallow- and deep-water reefs.
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Estimating Surface Area of Sponges and Marine Gorgonians as Indicators of Habitat Availability on Caribbean Coral Reefs