Mesophotic Coral Ecosystems

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MESOPHOTIC CORAL ECOSYSTEMS – A LIFEBOAT FOR CORAL REEFS? 45
Studies of the MCEs off La Parguera on the southwest coast of
Puerto Rico have been focused along the insular slope, located
approximately 10 km offshore (Figure 1). This area is located
within the La Parguera Natural Reserve, an area under nominal
management by the Puerto Rico Department of Natural and
Environmental Resources (Schärer-Umpierre et al. 2014). The
insular platform extending to the slope has an average depth
of 20 m and supports an extensive development of coral reefs,
seagrass beds andmangrove forests.The entire shelf and the shelf
edge have karst topography (Morelock et al. 1977). The shelf
break occurs at 20–35m in depth and supports a barrier reef with
spur and groove formations through which sand is transported
over the shelf edge (Morelock et al. 1977). Deep buttresses are
common between 45 and 65 m in depth, and a prominent
terrace occurs at approximately 80–90 m. Below 90 m, a steep
wall drops precipitously to 160 m (Sherman et al. 2010).
Geomorphology and geological processes strongly influence the
distribution and development of MCEs off La Parguera. Along
a 20 km stretch off La Parguera, only five sites were found to
have well-developed MCEs (Figures 1 and 2). As with shallow
coral reefs, sedimentation and bedload transport can restrict
reef development. At mesophotic depths, sedimentation is
generally low, but bedload transport down steep slopes plays a
significant role, limiting extensive coral development to areas
of topographic highs, where benthic organisms can settle
and survive. Off La Parguera, southeast-facing slopes were
exposed to direct wave impacts during past sea level rise. They
consequently have a shallower slope and are less rugose. In
contrast, southwest-facing slopes are steeper and have greater
rugosity, which helps channel sediment away from coral
outcrops. For this reason, well-developed MCEs off La Parguera
were found only on southwest-facing slopes (Figure 1).
3.10. La Parguera, Puerto Rico, USA
Richard S. Appeldoorn, University of Puerto Rico at Mayagüez, USA
David Ballantine, National Museum of Natural History, Smithsonian Institution and University of Puerto Rico at Mayagüez, USA
Ivonne Bejarano, University of Puerto Rico at Mayagüez, USA
Héctor Ruiz, University of Puerto Rico at Mayagüez, USA
Nikolaos Schizas, University of Puerto Rico at Mayagüez, USA
Wilford Schmidt, University of Puerto Rico at Mayagüez, USA
Clark Sherman, University of Puerto Rico at Mayagüez, USA
ErnestoWeil, University of Puerto Rico at Mayagüez, USA
Figure 1. Shelf edge and upper insular slope off La Parguera, Puerto Rico. Red arrows show those sites containing well-developed MCEs.
Primary study sites were Hole-in-the-Wall, a southwest-facing slope, and El Hoyo (blue arrow), a southeast-facing slope (sources Richard
S. Appeldoorn and Clark Sherman .
Puerto Rico - La Parguera shelf edge
0 2
Kilometres
1
Precipicio
Black Wall
Hole-in-the-Wall
El Hoyo
Buoy Baranca
La Parguera Shelf Edge
Puerto Rico