CANCELLED - A rapid estimation method for assessing reef habitat provided by sponges and octocorals on shallow and deep water reefs

Background/Question/Methods Shallow and deep-water reefs are important habitats in the Atlantic, and impart essential ecological functions for maintaining human economies. As reports of reef habitat degradation proliferate, the integrity, biodiversity and habitat sustainability of reef ecosystems are threatened. Ecologists are responding to the mounting evidence of reef decline by developing rapid assessment methods to evaluate changing environmental conditions. This information must be quickly provided to marine managers and policy makers to respond with decisions to mitigate habitat decline. Many assume scleractinians or stony corals are the only organisms that sustain important functions to fish and macroinvertebrate populations on oceanic reefs, but other organisms can contribute significant structural biomass and provide essential ecological functions. Marine sponges (Porifera) and octocorals (Gorgonaceae) contribute important structure-forming functions, particularly in areas where scleractinian corals are relatively rare or absent. A rapid assessment method was developed to evaluate the potential of octocorals and sponges to provide habitat and serve ecological functions to other invertebrates and fishes.

Results/Conclusions The total surface area of octocorals and sponges was estimated by considering their complex morphologies as three-dimensional shapes analogous to bushes, domes, flat crusts, among others. Morphologies were adapted to geometries that matched the shape of the organism. Conversion factors (CF) were assigned to each morphological type to account for the organism’s exposed surface reflected by its topographical structural complexity and vertical projection. Octocoral morphologies can resemble bushes with varying numbers of branches, two and three dimensional fans, hemispheres or encrusting forms. Sponge morphologies can resemble barrels, vases, spheres, tubes, or encrusting forms. In underwater surveys, octocorals and sponges were classified into basic shapes, with maximum height and diameter recorded. Total surface area for each organism was estimated by application of the morphologically appropriate CF to the underwater height and diameter measurements. Currently, total surface areas of scleractinian corals are being evaluated for use as biocriteria by the US Environmental Protection Agency. Protocols for employing sponge and octocoral surface areas will be evaluated as additional coral reef condition metrics for developing biocriteria to assess coral reef condition under the Clean Water Act.