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Richard S. AppeldoornClark Sherman, PhD, UPRM

Department of Marine Sciences
University of Puerto Rico
Mayaguez, Puerto Rico  00681‑9013

PHONE: (787) 899-2048 ext. 250
FAX: (787) 899-5500


Clark's research is focused on examining the geomorphology, physical structure and sediment dynamics of mesophotic coral ecosystems (MCE). NOAA multibeam bathymetry and diver observations are the primary tools for characterizing and analyzing the geomorphology of these habitats. Geomorphology of these settings exerts a fundamental control on downslope sediment transport and consequently the occurrence and distribution of MCEs. Data collected thus far for southwest Puerto Rico reveal a relationship between slope gradient, rugosity (or roughness) and orientation of the shelf margin, where more protected southwest-facing exposures are typically steeper with more irregular topography and have more abundant, extensive and diverse MCEs. The geomorphology of other areas around Puerto Rico and the US Virgin Islands is currently being examined so that a general model can be established to help predict likely MCE habitats for future research and protection.

There is little data on the physical structure of mesophotic coral ecosystems and the nature of lithic substrates in the mesophotic zone, which are necessary for the recruitment and settlement of the sessile organisms that make up MCEs. Lithic substrate samples collected by divers at depths of ~50 to 90 m are being examined to determine the varying roles of corals, calcareous algae and microbialites (lithified micritic crusts) in forming mesophotic lithic substrates. Future research efforts will focus on coring of these habitats to reveal their internal structure and formational history.

Sediment transport is known to exert an important control on the development of both shallow shelf reefs and deeper MCEs on insular slopes. However, little data exists that characterizes and quantifies rates and patterns of downslope sediment transport in the mesophotic zone. To this end, an array of sediment traps has been deployed at MCE sites at depths of ~50 and 70 m to characterize and quantify spatial and temporal patterns in both vertical sedimentation from the water column and downslope bedload transport of sedimentary material. In combination with benthic cover data, sediment trap data will document the interrelationships between slope geomorphology, sediment transport and the distribution of MCEs.

Other CCRI-Sponsored Research (Link)