Abstract

The Pinnacle reefs are deep water (60–110 m) natural rock reefs that project up to 20 m from the seafloor on the edge of the continental slope in the northern Gulf of Mexico. These mesophotic reef habitats are home to a diverse invertebrate and fish community. From September to October 2014, a stratified random ROV video survey was used to count and identify benthic invertebrate species from 3 reef types: low (0-3m), medium (4-10m) and high (>10m) vertical relief, and from 2 reef habitats: reef top and reef slope. Still photos taken from video transects were analyzed to obtain percent cover and density per m2 of invertebrate species. The ahermatypic, heterotrophic benthic community is dominated by gorgonians, antipatharians, scleractinian corals, comatulid crinoids, and sponges. Mean total benthic percent coverage was 28.0%, with a maximum of 60.3% coverage. Primary taxa include Rhizopsammia manuelensis (mean: 4.9%), Antipathes atlantica (1.9%), Bebryce sp. (1.2%), Swiftia exserta (1.1%), and Nicella sp. (1.1%). Benthic community composition differed among reef relief types (PERMANOVA, Pseudo-F = 2.66, p = 0.002) with high relief reefs supporting greater abundances than low relief reefs (Z = -4.49, p < 0.0001). Benthic communities also differed between reef top and slope habitats (PERMANOVA, Pseudo-F = 8.87, p = 0.001). Environmental factors of depth, sedimentation, and geographical location also contributed to variance in community composition (RELATE, Rho = 0.36, p = 0.001). Total benthic percent cover was correlated with total fish abundance (r = 0.37, n = 140, p < 0.0001).

PDF Preview