Florida's Deep Reefs

Introduction

A long swathe of hundreds of high-relief mounds and pinnacles, constructed chiefly by Lophelia pertusa, extend along the base of the Florida-Hatteras slope in 500-866 m from southern Georgia into the Strait of Florida as far south as Jupiter, FL. Topographic highs, most with at least some coral development, are abundant and nearly continuous from the Jacksonville area to south of Cape Canaveral. John Reed and others have mapped over 300 features from 8 to 168 m in vertical relief along a 222-km stretch from Jacksonville to Jupiter. So far, over ten percent have been ground-truthed via submersible or ROV, confirming the presence of L. pertusa and/or E. profunda. Those in the northern portion of this area off Jacksonville and southern Georgia are primarily rock mounds capped with coral, coral rubble and other attached fauna.

Geology

The features from south of St. Augustine to Jupiter appear to be chiefly sediment and coral rubble mounds capped with dense 1-m tall thickets of L. pertusa and E. profunda, some M. oculata and varying amounts of coral debris and dead standing coral.  As an example, a L. pertusa mound off Cape Canaveral is 44 m high and rises to a series of ridged peaks in 713-722 m. The lower southern flank is a 10-20o sandy slope with 1-3 m-high ridges supporting ~50% cover of L. pertusa thickets, chiefly 1-m tall dead standing colonies topped by ~1-10% cover of living colonies on the outer edges. Most of the coral is intact with little broken dead coral rubble in the rippled sand between.  The upper slope steepens first to 45o and then 70-80o near the top. The pinnacle crest is a narrow 5-10-m-wide ridge with covered with dead coral thickets and up to 20% living colonies, both L. pertusa and E. profunda, up to 90 cm tall.

Along the deep axis of the Strait, at least as far south as Miami, E. profunda builds low muddy sand and coral rubble mounds up to 50 m across and 0.3-4.5 m high with 0-10% living coral cover. They occur as shallow as 719 m off Miami, but begin in 773 m off Fort Lauderdale. The deepest reach 825 m in the center of the Strait. These features are separated by areas of dense to sparse coral rubble and flat or rippled sediment. AUV and submersible observations have also revealed five areas of high-relief coral mounds and pinnacles closer to the Great Bahama Bank between the base of the Miami Terrace and Bimini I.

Biology

In addition to the stony corals, deep coral mound fauna includes stylasterid lace corals, octocorals (Plumarella pourtalesi, Isidella sp., Keratoisis flexibilis, Eunicella modesta, Anthomastus sp. and Pseudodrifa nigra), demosponges (Pachastrellidae, Desmacellidae and fan Phakellia sp.), hexactinellid glass sponges (Aphrocallistes beatrix, Hertwigia falcipera, Heterotella sp. and Hyalonema sp.), pencil urchins (Cidaridae), pancake urchins (Araeosoma sp.), feather stars (Zenometra columnaris, Comatilia iridometriformis)and decapod crustaceans (Chaceon fenneri, Eumunida picta). These sites appear to support a more diverse invertebrate fauna than those further north (Steve Ross, unpubished). The dominant fishes are eels (Synaphobranchus spp.) andrattails (Nezumia sclerorhynchus).

Although substantial trawling and dredging records exist throughout the Strait, most results are scattered throughout the literature for individual taxonomic groups, and neither the invertebrate nor fish fauna of deep coral habitats has been adequately surveyed. Known species richness is almost certainly much greater than currently recognized.

Habitats

Porifera

HEXACTINELLIDA

Cnidaria

SCLERACTINIA

ANTIPATHARIA

OCTOCORALLIA

Crustacea

Fishes