II.
Introduction
This work is an effort towards characterization of deep reefs and associated marine
communities from Puerto Rico (PR) and the U. S. Virgin Islands (USVI). It includes an
assessment of their geographic distribution, bathymetric features, benthic habitat types, and
a taxonomic inventory of species previously reported from deep reefs in this region, with
particular emphasis on corals. Available geo-physical, hydrographic and biological
information has been geo-referenced and included on a GIS map atlas of the U. S.
Caribbean EEZ. A pilot field survey of marine communities associated with a deep
hermatypic reef system in Isla Desecheo (west coast of PR) forms part of this investigation,
and expands upon an ongoing program of coral reef community characterizations and
monitoring sponsored by NOAA through the Department of Natural and Environmental
Resources of Puerto Rico (DNER) (García-Sais et al., 2001 a, b, c, d) and the Division of
Coastal Zone Management of the USVI (Nemeth et al., 2002, Jeffrey et al, 2005).
Deep reefs are hard ground structures that provide underwater topographic relief and serve
as important habitats for marine communities, influencing ecosystem biodiversity and
productivity beyond the shelf edge. The reef habitat at depths between 60 – 150 meters has
been defined as the “twilight zone”, the upper limit being the approximate maximum depths
to which hermatypic corals dominate reef structure, and the lower limit the maximum depth
to which the coral reef extends (Pyle, 2000). In Jamaica, and perhaps other islands of the
northern Caribbean, hermatypic (reef building) corals occur down the insular slope to
maximum depths of about 100 meters (Goreau and Wells, 1967), but are mostly present as
isolated colonies without contributing significantly to the formation of reefs. Still, the deep
hermatypic coral fauna represents an important genetic reservoir that may serve for
replenishment of the declining shallow water scleractinian coral assemblage.
At depths below the range of hermatypic coral and algal growth, available hard primary
substrate is the basis for attachment and growth of sponges, ahermatypic (azooxanthellate)
corals, echinoderms, and other encrusting (sessile-benthic) biota. Ahermatypic corals are
known to create true “coral reefs” in deep cool waters of the oceans in regions of strong
currents and/or zones of upwelling. Reefs formed by ahermatypic corals are also called
lithoherms, bioherms, or coral banks. The ivory tree coral, Oculina varicosa Leseur forms
massive coral banks along the upper edge of the Florida-Hatteras slope at depths between
70 – 100 m, and water temperatures ranging between 7.5 – 26.5 °C (Reed, 1980). The
geographic distribution of the Oculina banks appears to be confined to the Florida shelf.
4
Introduction
This work is an effort towards characterization of deep reefs and associated marine
communities from Puerto Rico (PR) and the U. S. Virgin Islands (USVI). It includes an
assessment of their geographic distribution, bathymetric features, benthic habitat types, and
a taxonomic inventory of species previously reported from deep reefs in this region, with
particular emphasis on corals. Available geo-physical, hydrographic and biological
information has been geo-referenced and included on a GIS map atlas of the U. S.
Caribbean EEZ. A pilot field survey of marine communities associated with a deep
hermatypic reef system in Isla Desecheo (west coast of PR) forms part of this investigation,
and expands upon an ongoing program of coral reef community characterizations and
monitoring sponsored by NOAA through the Department of Natural and Environmental
Resources of Puerto Rico (DNER) (García-Sais et al., 2001 a, b, c, d) and the Division of
Coastal Zone Management of the USVI (Nemeth et al., 2002, Jeffrey et al, 2005).
Deep reefs are hard ground structures that provide underwater topographic relief and serve
as important habitats for marine communities, influencing ecosystem biodiversity and
productivity beyond the shelf edge. The reef habitat at depths between 60 – 150 meters has
been defined as the “twilight zone”, the upper limit being the approximate maximum depths
to which hermatypic corals dominate reef structure, and the lower limit the maximum depth
to which the coral reef extends (Pyle, 2000). In Jamaica, and perhaps other islands of the
northern Caribbean, hermatypic (reef building) corals occur down the insular slope to
maximum depths of about 100 meters (Goreau and Wells, 1967), but are mostly present as
isolated colonies without contributing significantly to the formation of reefs. Still, the deep
hermatypic coral fauna represents an important genetic reservoir that may serve for
replenishment of the declining shallow water scleractinian coral assemblage.
At depths below the range of hermatypic coral and algal growth, available hard primary
substrate is the basis for attachment and growth of sponges, ahermatypic (azooxanthellate)
corals, echinoderms, and other encrusting (sessile-benthic) biota. Ahermatypic corals are
known to create true “coral reefs” in deep cool waters of the oceans in regions of strong
currents and/or zones of upwelling. Reefs formed by ahermatypic corals are also called
lithoherms, bioherms, or coral banks. The ivory tree coral, Oculina varicosa Leseur forms
massive coral banks along the upper edge of the Florida-Hatteras slope at depths between
70 – 100 m, and water temperatures ranging between 7.5 – 26.5 °C (Reed, 1980). The
geographic distribution of the Oculina banks appears to be confined to the Florida shelf.
4