Gulf of Mexico Science Volume 33 Article 3 Number 1 Number 1 2016 Validation of Image-Based Species Identifications of Black Corals (Order Antipatharia) on Mesophotic Rocks Marissa F. Nuttall Flower Garden Banks National Marine Sanctuary Dennis M. Opresko Smithsonian Institution Emma L. Hickerson Flower Garden Banks National Marine Sanctuary DOI: 10.18785/goms.3301.03 Follow this and additional works at: https://aquila.usm.edu/goms Recommended Citation Nuttall, M. F., D. M. Opresko and E. L. Hickerson. 2016. Validation of Image-Based Species Identifications of Black Corals (Order Antipatharia) on Mesophotic Rocks. Gulf of Mexico Science 33 (1). Retrieved from https://aquila.usm.edu/goms/vol33/iss1/3 This Article is brought to you for free and open access by The Aquila Digital Community. It has been accepted for inclusion in Gulf of Mexico Science by an authorized editor of The Aquila Digital Community. For more information, please contact [email protected]. Nuttall et al.: Validation of Image-Based Species Identifications of Black Corals Gulf of Mexico Science, 2016(1), pp. 26–37 Validation of Image-Based Species Identifications of Black Corals (Order Antipatharia) on Mesophotic Reefs MARISSA F. NUTTALL,DENNIS M. OPRESKO, AND EMMA L. HICKERSON Biodiversity, an important measure of ecosystem health, is challenging to ascertain using sampled specimens in remote deep-sea environments. As image-based identifica- tions become a predominant method for deep-sea species characterizations, there is a need to evaluate the accuracy of species- and genus-level identifications from video and still images to provide a reliable measure of biodiversity. This study presents a validation of the ability to make accurate image-based identifications of black coral species in the northwestern Gulf of Mexico from standard-definition video collected by a remotely operated vehicle. Results indicate that the greatest number of misidentifica- tions occurred at species-level groupings (42.2% error), whereas genus-level groupings possessed 12.0% error, and identifications to kappa groupings had no error. We recommend genus-level groupings to maintain accurate identifications while maximiz- ing estimates of biodiversity. INTRODUCTION (ROVs), further advancements in characterizing and understanding these habitats are being made cosystem health is valuable in understanding every year. Historically, specimen collections E the stressors, identifying causes, and poten- and distribution information of mesophotic and tially improving environmental management of deep-sea corals has primarily come from fisheries an ecosystem (Rapport et al., 1998). A “healthy” records, bycatch, and museum collections (Bryan ecosystem is considered stable and sustainable and Metaxas 2007). Although current technolo- (Costanza, 1992). Although there are multiple gies allow for direct sampling of specimens, measures that aim to assess ecosystem health, specimen sampling is still limited by the capacity biodiversity is considered a valuable measure, as of the sampling tool and by a conscious conser- high biodiversity is considered to enhance the vation as we understand the fragility of many of stability, resilience, and productivity of some these organisms. However, these same sampling ecosystems (Johnson et al., 1996; Folke et al., tools often have the ability to collect vast amounts 2004). Species composition is also an important of image-based data, with improving resolution, component in understanding ecosystem health, as technology improves, over time. The avail- as a community comprised of multiple opportu- ability, ease of collection, and noninvasive nature nistic species may be an indicator of stress. In of image-based data are helping to accelerate remote environments, these measures can be estimates of biodiversity in mesophotic and deep- challenging to ascertain. sea habitats. However, before image-based iden- Mesophotic coral ecosystems (MCEs) occur tifications can be applied in research, their in the lower portion of the photic zone in tro- accuracy needs to be tested. A validation process pical and subtropical regions, ranging from 40- to is presented in this paper for black corals on 150-m depth (Puglise et al., 2009). The upper mesophotic reefs in the northwestern Gulf of depth limit of this zone represents the region Mexico. in which a shift is observed in the biological Black corals (Cnidaria: Anthozoa: Hexacorallia: assemblages (Kahng et al., 2010). Because of Antipatharia) are slow-growing sessile species, their unique depth range, MCEs are considered potentially representing some of the oldest living to be extensions of shallow-water coral ecosys- animals on Earth, with colonies dated to over tems and deepwater assemblages, in addition to 4,000 yr old (Roark et al., 2009). Black corals are possessing their own unique biotic assemblages important components of the mesophotic and (Hinderstein et al., 2010). Like deep-sea habitats, deep-sea benthic communities throughout the MCEs have received relatively little attention in world. They are considered ecosystem engineers, comparison with shallow-water habitats because providing valuable three-dimensional habitat for of the challenges associated with accessing numerous associated fauna, fish, and invertebrate these environments. However, with the growing species (Jones et al., 1994; Hourigan et al., 2007). accessibility of resources needed to study these Because of their life history and complex mor- environments, such as remotely operated vehicles phology, these corals are particularly vulnerable E 2016 by the Marine Environmental Sciences Consortium of Alabama Published by The Aquila Digital Community, 2016 1 Gulf of Mexico Science, Vol. 33 [2016], No. 1, Art. 3 NUTTALL ET AL.—VALIDATION OF IMAGE-BASED IDENTIFICATIONS 27 Fig. 1. Map showing the eight locations from which samples were collected in the northwestern Gulf of Mexico. Sites shown are 1. West FGBNMS, 2. Horseshoe Bank, 3. East FGBNMS, 4. 29 Fathom Bank, 5. 28 Fathom, 6. Rankin Bank, 7. Bright Bank, and 8. Geyer Bank. to unsustainable harvesting and environmental skeletal branching mode and pinnulation, polyp threats (Bo et al., 2009). Worldwide, black corals structure and size, and, in particular, spine mor- are threatened by harvesting for the commercial phology (Warner 1981; Perez et al., 2005; France jewelry trade and oriental medicinal purposes, et al., 2007). The ability to obtain high-resolution deepwater fishing practices, dredging, and hy- images through scanning electron microscopy drocarbon exploration and dispersion chemicals (SEM) of the skeleton has enhanced the use (Fossa et al., 2002; Hall-Spencer et al., 2002; of spine morphology as a taxonomic character Mortensen and Buhl-Mortensen, 2004; Roark et al., (Wagner et al. 2010). However, this technique of 2009; Bai et al., 2011, Silva et al., 2015). Established species identification requires that a tissue sample black coral fisheries exist in the Caribbean, of the colony be collected. For slow-growing, com- Hawai‘i, and Asia (Grigg, 1975, 1976, 1993; mercially valuable, and protected species, like black Castorena and Metaca, 1979; Guitart et al., 1997; corals, the ability to make noninvasive image-based Huang and Ou, 2010). Although recent manage- identifications is particularly valuable. As technol- ment strategies aim to make these fisheries sustain- ogy improves, the ability to capture high-resolution able, historically, they have been overexploited images of the seafloor is also improving, allowing (Bruckner et al., 2008; Tsounis et al., 2010). researchers to obtain clear in situ images of Multiple studies have noted the presence and organisms. National Oceanographic and Atmo- distribution of black corals on reefs and banks spheric Administration’s (NOAA) Flower Garden throughout the northwestern Gulf of Mexico Banks National Marine Sanctuary (FGBNMS) has (Rezak et al., 1985; Opresko and Cairns, 1992; been working to develop image-based identifica- Cairns et al., 1994; Brooke and Schroeder, 2007; tion catalogs for multiple mesophotic and deep-sea Robbart et al., 2009). However, no comprehen- species for the northwestern Gulf of Mexico. This sive study of this order has been conducted in paper represents a validation process for FGBNMS the region to date. Of the 39 species of black black coral catalog (Hickerson et al., 2007, coral reported from the western Atlantic, 30 of Opresko et al., 2016). those have been documented in the Gulf of Mexico (Opresko 2009). MATERIALS AND METHODS Black corals are noncalcareous corals with Black coral specimens were collected using organic skeletons comprised of chitin and protein. a Phantom S2 ROV on four research cruises to Traditional species descriptions of black corals eight banks in the northwestern Gulf of Mexico focus on morphological characters, including (Fig. 1) between 2011 and 2012. Specimens were https://aquila.usm.edu/goms/vol33/iss1/3 2 DOI: 10.18785/goms.3301.03 Nuttall et al.: Validation of Image-Based Species Identifications of Black Corals 28 GULF OF MEXICO SCIENCE, 2016, VOL. 33(1) TABLE 1. Comparison of image-based identification and laboratory identification. Table shows sample size, based on in situ identification, and the percent composition of image-based identifications by laboratory identification. Laboratory species identifications In situ Sample Antipathes Antipathes Elatopathes Acanthopathes Acanthopathes sp., Aphanipathes Tanacetipathes identification size furcata gracilis/atlantica abietina thyoides cf. A. thyoides