Methods for the Characterization of Deep-Sea Benthic Megafauna in the Vicinity of the Deepwater Horizon Macondo Well

Soft-sediment benthic environments are amongst the largest marine ecosystems in the world and play important roles in many ecosystem functions. In recent years, exploitation of resources and unintentional impacts on deep-sea benthic environments has increased. The Deepwater Horizon oil spill of 2010 in the northern Gulf of Mexico (GoM) represented a prime example of this. The oil spill not only highlighted deficiencies of data and information on baseline conditions, but also represented an opportunity to learn more and develop better methods for the future. Deep-sea imaging platforms such as autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) have been growing in popularity as a minimally invasive means of exploring the deep-sea; and the use of industrial resources has increased due to availability of these technologies in the GoM region. This dissertation explores the use of industrial-based AUVs and ROVs as a means of studying benthic megafauna in the vicinity of the Deepwater Horizon Macondo well, and outlines a methodology that can be applied to current and future environmental monitoring efforts. Industrial ROVs were found to be generally superior to AUVs for specifically studying benthic megafauna. Simulations comparing different radial survey designs found that designs featuring longer transects with smaller transect spacing were more effective at estimating animal populations. In particular, the 15°, 250 m long transect radial survey design employed by the ROVs in this study was found to perform well for surveying benthic megafauna. To improve collection and analysis of the wealth of data extracted from the imagery, a customized database system was developed for use in this study and for similar future studies. Data collected via ROV one year after the oil spill was used to characterize benthic megafaunal communities and evaluate potential influences on them. It was found that community composition was primarily related to depth and, to a lesser degree, location in the northern GoM and anthropogenic disturbance to the seafloor. Overall, the methodology and results explored here represent an opportunity to standardize and improve future environmental monitoring efforts of this kind in the GoM and beyond

Exploration of the Southern California Borderland

E/V Nautilus cruise NA075 returned to the Southern California Continental Borderland, an area that remains largely unexplored. Part of the broader North America-Pacific plate boundary, this region extends ~300 km west of the San Andreas Fault and displays an unusually rugged physiography. During the cruise, the multibeam sonar mapped ~5,200 km2 of seafloor, and ROVs Hercules and Argus were deployed for 16 dives to explore geological and biological targets (Figure 1) and collect samples

Workshops Report for Mesophotic and Deep Benthic Community Fish, Mobile Invertebrates, Sessile Invertebrates and Infauna

Two workshops with subject matter experts in the appropriate fields, were held in November and December 2021 to elicit guidance and feedback from the broader mesophotic and deep benthic scientific community. These workshops focused on best practices/approaches and identifying data gaps relative to habitat assessment and evaluation goals of the Mesophotic and Deep Benthic Community (MDBC) restoration portfolio. The first workshop was a combined effort of the Habitat Assessment and Evaluation (HAE) Project Team and the Deepwater Horizon (DWH) Program. Industrial Economics, Inc. (IEc) provided extensive workshop planning, organizing, execution, and facilitation support during all stages of the workshop. Based on a questionnaire sent to scientists in August, 2021, the workshop focused on fish and mobile invertebrate habitat associations, abundance trends, community metrics, and food web functionality. Topical presentations and discussions focused not only on demersal fish and mobile invertebrates that are directly associated with mesophotic and deep benthic habitats, but also considered water column species and communities that benefit from these habitats more broadly. The second workshop, intended to complement the first workshop, focused on identifying best practices and critical information gaps for key community metrics, larval dispersal modeling, connectivity, effects and variability of environmental parameters, and recovery trajectories of corals, infauna, and other sessile invertebrates. Through literature review, internal HAE scientists considered these topics to be critical for restoration success. Products from the literature review included topical summaries (see Appendix B) that summarized the current state-of-the-science and provided the framework for the workshop. Information generated from the workshops will assist the MDBC HAE Project, and more broadly the DWH Program, identify data gaps and develop a suite of best practices for restoration activities