MEPS 583:121-136 (2017)  -  DOI: https://doi.org/10.3354/meps12336

ABSTRACT: The mesophotic coral ecosystem (MCE) of the eastern Gulf of Mexico hosts diverse invertebrate and fish fauna across an array of hard-ground features. However, the extent of the potential MCE habitat in the region is poorly constrained. Maximum entropy modeling was used to predict the spatial extent of mesophotic azooxanthellate octocorals and antipatharians within the mesophotic area located between Mississippi (Pinnacle Trend Area) and the mid-continental shelf and upper slope of Florida, eastern Gulf of Mexico. Habitat prediction models were generated using geo-referenced, coral-presence records obtained by classifying photographic samples with co-located geophysical data, oceanographic variables, and atmospheric variables. Resulting models were used to predict the extent of suitable habitat in the study area. An independent set of presence records was used to test the model performance. Results (general and by taxon) predict that suitable areas for MCE exceed 400 km² and occur along carbonate mounds and paleo-shoreline ridges (hard substrata and high surface rugosity). Reduced amounts of fine sediments, surrounding waters rich in chromophoric dissolved organic matter (CDOM), and downwelling currents also increased predicted suitability. The model significantly exceeded random performance and predicted that surface rugosity and CDOM are the most important variables contributing to coral habitat. Areas of hard substrate within the study area that were not identified as coral habitat by the model suggest that mesophotic sea fans and sea whips apparently depend as much on the chemical and physical conditions (e.g. currents that transport oxygen and food) as on hard substrata for settlement.

KEY WORDS: Habitat suitability · Mesophotic · Maximum entropy modeling · Corals · Octocorals · Antipatharian · Eastern Gulf of Mexico · Maxent