From Loh, T.-L., and Pawlik, J.R. (2014) PNAS. See paper for citations referred to below:
Study Sites and Benthic Community Surveys. Surveys were conducted on coral reefs at 69 sites from 12 countries across the Tropical Northwestern Atlantic marine province (referred to herein as "Caribbean" for brevity) from 2008 to 2012. At each location, sponge community data and fish densities were recorded at 3-11 geographically distinct sites (>2 km apart) by a team of three to four that only included personnel from among the same five surveyors to minimize interobserver subjectivity. Transect lines were laid out along a contiguous section of the reef at 10-20 m (except for the shallow reefs off Bocas del Toro, Panama, and two sites off Key Largo, FL, 2-7 m). Surveys of sponge cover were carried out using a technique adapted from past studies (35) by evenly placing a 1 × 1 m2 quadrat at 5 points along a 20-m transect line, with 5 replicate transects laid end-to-end at the same depth (total of 25 quadrats and 625 points per survey site). All sponges were identified to species (36), and when necessary, identifications were confirmed by Sven Zea (Universidad Nacional de Colombia, Santa Marta, Colombia) using microscopic examination of spicule mounts or tissue sections. Sponge species were categorized as chemically defended, consistently undefended, or variably defended based on data from laboratory feeding assays using the bluehead, Thalassoma bifasciatum, that were either conducted in the past (11, 26, 28) or performed for this study using the same methods (Table S2).