Weinstein et al. 2014

scientific article | Geomorphology | open access Open access small

Mesophotic bioerosion: Variability and structural impact on US Virgin Island deep reefs

Weinstein DK, Smith TB, Klaus JS

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Mesophotic reef corals, found 30–150 m below sea level, build complex structures that provide habitats for diverse ecosystems. Whereas bioerosion is known to impact the development and persistence of shallow reef structures, little is known regarding the extent of mesophotic bioerosion or how it might affect deeper reef geomorphology and carbonate accretion. Originally pristine experimental coral substrates and collected coral rubble were both used to investigate the variation and significance of mesophotic coral reef bioerosion south of St. Thomas, U.S. Virgin Islands. Bioerosion rates were calculated from experimental coral substrates exposed as framework for 1 and 2 years at four structurally distinct mesophotic coral reef habitats (between 30 and 45 m) as well as at a mid-shelf patch reef (21 m) and a shallow fringing patch reef (9 m). The long-term effects of macroboring were assessed by examining coral rubble collected at all sites. Overall, differences in bioerosional processes were found between shallow and mesophotic reefs. Increases in bioerosion on experimental substrates (amount of weight lost) were related to both decreasing seawater depth and increasing biomass of bioeroding parrotfish. Significant differences in coral skeleton bioerosion rates were also found between the transitional mesophotic reef zone (30–35 m) and the upper mesophotic reef zone (35–50 m) after 2 years of exposure, ranging from − 19.6 to 3.7 g/year. Total coral rubble macroboring was greater at most deep sites compared to shallower sites. Bioerosional grazing was found to dominate initial substrate modification in reefs 30.7 m and shallower, but sponges are believed to act as the main time-averaged long-term substrate bioeroders in reefs between 35 and 50 m. Although initial substrate bioerosion rates of a uniform substrate were relatively homogeneous in the 35–50 m depth zone, comparison of site composition suggests that mesophotic bioerosion will vary depending on the amount, location, and type of available substrate, and the duration both coral rubble and in situ coral framework are exposed on the seafloor. These variations may exaggerate pronounced structural differences in mesophotic reef habitats that experience few other methods of erosion.

Research sites

10.1016   j.geomorph.2014.03.005
Meta-data (pending validation)
Depth range
9- 45 m

Mesophotic “mentions”
84 x (total of 6692 words)

Ecology Geomorphology Long-term monitoring

Research focus
Overall benthic (groups) Fishes Other invertebrates

US Virgin Islands

Research platforms
Diving - Technical Open-Circuit Diving - Technical Rebreather
Author profiles
Tyler Smith ( 21 pubs)
David Weinstein ( 5 pubs)