Growth rates, densities, and distribution of Lophelia pertusa on artificial structures in the Gulf of Mexico Elizabeth A. Larcom a , Danielle L. McKean a , James M. Brooks b , Charles R. Fisher a,n a Department of Biology, The Pennsylvania State University, USA b TDI Brooks International, USA article info Article history: Received 15 April 2013 Received in revised form 26 November 2013 Accepted 2 December 2013 Available online 1 January 2014 Keywords: Lophelia pertusa Growth rates Gulf of Mexico Oil rigs Hydrocarbon installations Ship wrecks Depth range Image analysis abstract Using industry inspection video and ROV imaging, we examined Lophelia pertusa (Linnaeus 1758) on 10 artificial structures of known ages (9 to 100 years) in the northern Gulf of Mexico (GoM). Five different types deep-water energy installations with depths ranging from 320 to 995 m, and three shipwrecks with depths ranging from approximately 530 to 615 m, were examined. Density, depth ranges, and growth rates of L. pertusa colonies were calculated from video and image analysis. L. pertusa colonies were present on all structures examined. Minimum calculated growth rates for the largest colonies ranged from 0.32 to 3.23 cm/yr on the different structures. The shallowest depth at which L. pertusa was observed was 201 m and the deepest was 801 m, considerably expanding the known depth range of this species in the northern GoM. Colony density varied with structure type, age, and depth, with the highest density between 503 and 518 m on the single structure that spanned the entire depth range of occurrence of L. pertusa observed in this study. L. pertusa colonies growing on thinner and deeper installations appear to have higher colonization rates, i.e. to develop higher densities over a shorter time period, compared to those on shallower and more massive types of installations. However, on average, colonies have slower growth rates on these installations than colonies on more massive, shallower installations (compliant and solid installations). In general, the calculated minimum growth rates were higher on the installations than on the shipwrecks, which were substantially older. A continuum of colony sizes was documented on all installations, suggesting multiple settlement events. L. pertusa thickets were observed on the oldest anthropogenic structures, with most of the components of these structures covered by colonies of L. pertusa. Brown, orange, and mottled color-variants were documented for the first time in the GoM. All installations examined for this study were colonized by L. pertusa and it is likely that most artificial surfaces in appropriate depths in the GoM will be as well. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Lophelia pertusa (Linnaeus 1758) is a cosmopolitan, azoox- anthellate, cold-water, scleractinian coral. First order limits on the distribution of L. pertusa include the availability of hard substrate, presence of permanent or episodically strong currents, the depth of the storm wave base, and the location of the thermocline (Freiwald, 2002). The bottom end of L. pertusa depth distribution is limited by the oxygen minimum zone in the North Sea (Freiwald, 2002). Perhaps reflecting metabolic oxygen require- ments, L. pertusa is particularly sensitive to increased tempera- tures (Dodds et al., 2007) and has an upper temperature limit of 12 1C in the North Sea (Rogers, 1999). L. pertusa can form substantial colonies up to or greater than 2 m in height and 1.5 m across in the Northern Gulf of Mexico (GoM) (Schroeder, 2002). These single colonies often grow together to form extensive reefs. Though most recent literature has focused on natural L. pertusa reefs (Brooke and Schroeder, 2007; Freiwald, 2002; Freiwald and Henrich, 1997; Rogers, 1999; Schroeder, 2002; Sulak, 2008; Wilson, 1979), L. pertusa growth on anthropogenic substrates such as sub-sea cables (Duncan, 1877; Wilson, 1979), energy installations (Bell and Smith, 1999; Gass and Roberts, 2006; Schroeder et al., 2005) and ship wrecks (Church et al., 2007; Roberts et al., 2003), is well documented. A recent search of the Bureau of Ocean Energy Management's (BOEM) Platform Structures Query (Bureau of Ocean Energy Management, 2012) found 65 installations with surface compo- nents in the GoM in water depths greater than 200 m, (deep enough to encompass the minimum known depth range of L. pertusa in the GoM). In 1997, “deep” (depths greater or equal to 305 m (1000 ft)), or “ultra-deep” (depths greater or equal to Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dsri Deep-Sea Research I 0967-0637/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dsr.2013.12.005 n Correspondence to: Department of Biology, The Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802-5301, United States. Tel.: þ1 814 865 3365. E-mail address: cfisher@psu.edu (C.R. Fisher). Deep-Sea Research I 85 (2014) 101–109