Determining the Extent and Characterizing Coral Reef Habitats of the Northern Latitudes of the Florida Reef Tract (Martin County)

Abstract

Climate change has recently been implicated in poleward shifts of many tropical species including corals; thus attention focused on higher-latitude coral communities is warranted to investigate possible range expansions and ecosystem shifts due to global warming. As the northern extension of the Florida Reef Tract (FRT), the third-largest barrier reef ecosystem in the world, southeast Florida (25–27° N latitude) is a prime region to study such effects. Most of the shallow-water FRT benthic habitats have been mapped, however minimal data and limited knowledge exist about the coral reef communities of its northernmost reaches off Martin County. First benthic habitat mapping was conducted using newly acquired high resolution LIDAR bathymetry and aerial photography where possible to map the spatial extent of coral reef habitats. Quantitative data were collected to characterize benthic cover and stony coral demographics and a comprehensive accuracy assessment was performed. The data were then analyzed in a habitat biogeography context to determine if a new coral reef ecosystem region designation was warranted. Of the 374 km2 seafloor mapped, 95.2% was Sand, 4.1% was Coral Reef and Colonized Pavement, and 0.7% was Other Delineations. Map accuracy assessment yielded an overall accuracy of 94.9% once adjusted for known map marginal proportions. Cluster analysis of cross-shelf habitat type and widths indicated that the benthic habitats were different than those further south and warranted designation of a new coral reef ecosystem region. Unlike the FRT further south, coral communities were dominated by cold-water tolerant species and LIDAR morphology indicated no evidence of historic reef growth during warmer climates. Present-day hydrographic conditions may be inhibiting poleward expansion of coral communities along Florida. This study provides new information on the benthic community composition of the northern FRT, serving as a baseline for future community shift and range expansion investigations.

Potential Habitat of Acropora spp. on Reefs of Florida, Puerto Rico, and the US Virgin Islands

“…in southern Martin County is unlikely due to unique hydrodynamics present in this region. A recent study by Walker and Gilliam (2013) suggests the unlikelihood of northern expansion of tropical coral communities into the Martin County region due to frequent and intense upwelling events that occur north of the Bahamas Fault Zone (Klitgord et al, 1984;Pitts, 1999;Pitts and Smith, 1997;Smith, 1983). Coral communities north of this fault zone are restricted to cold tolerant species such as Siderastrea and Oculina (Colella et al, 2012;Lirman et al, 2011;Walker and Gilliam, 2013).…”

Objective automated classification technique for marine landscape mapping in submarine canyons

“…Parameters yielded by the GIS software must be considered with care, and not simply included by default. For example, hillshade is often used to aid in the identification of seafloor features (Walker and Gilliam, 2013). Although it is a derivative of multibeam bathymetry, hillshade is not considered as an abiotic variable, even if it can be a good indicator for the correlation between the seabed and a (residual, unidirectional) current.…”

Fecundity and sexual maturity of the coral Siderastrea siderea at high latitude along the Florida Reef Tract, USA

“…). However, the high latitudinal segment of the Florida Reef Tract (FRT) from the upper Florida Keys, Key Largo (25°N), through Martin County, Stuart (27°N), is largely a continuous reef feature connected to the more developed southern reefs of the Florida Keys (24.5°N) (Walker & Gilliam ). It represents an uninterrupted transition from a typical coral reef to a sparsely populated, low diversity coral community over a small geospatial scale (~200 km) (Moulding ; Banks et al.…”

“…; Rubin et al. ; Walker & Gilliam ). In the northern terminus of the reef tract (27°N), a transition from subtropical to temperate habitat occurs (Lugo et al.…”

“…In the northern terminus of the reef tract (27°N), a transition from subtropical to temperate habitat occurs (Lugo et al. ; Walker & Gilliam ). While the general reproductive ecology of some major hermatypic corals is documented at high latitudes of the FRT ( Acropora cervicornis , Siderastrea siderea, Solenastrea bournoni , Stephanocoenia intersepta, and Oculina varicosa ) (Vargas‐Ángel et al.…”