Abstract

Cryptic invertebrates are a little studied part of tropical coral reef ecosystems, despite their significant contribution to coral reef biomass and biodiversity. In order to assess means of sampling these cryptofauna and begin a census of present and common taxa, coral rubble traps were deployed at three sites in St. Thomas, USVI for two durations (14 and 28 days) near the University of the Virgin Islands. Two sites were onshore fringing reefs, with one relatively flat and Montastraea sp. dominated (5 – 10 m deep) and the other of mixed coral and steeply sloping 10 – 15 m deep; a third site was a fringing reef on an offshore cay of mixed coral 10 – 15 m deep. We tested the hypothesis that invertebrate communities/relative abundances are different by site but not sampling time. From the 18 traps, 246 individual motile invertebrates were sampled, representing 31 Operational Taxonomic Units (OTUs). The ten most common OTUs accounted for 86.59% of specimens, with arthropods making up the majority of specimens (82.52%) and consisting of 13 OTUs. Shannon diversity index H’ was calculated and then analyzed in a two-way crossed ANOVA for site and time; time was a significant factor (p = 0.0146). Average H’ increased between 14 and 28 days (0.456 and 0.655, respectively). Results from PERMANOVA showed only site to have a significant effect on the number of specimens per taxon (permutation p = 0.0435). The significant effect of time on H’ implies colonization new substrate to be on going within the time of deployment, while the difference among sites is evidence that different reefs, even in close proximity to one another, are affected differently by drivers of biodiversity and relative abundances of cryptic invertebrates.

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