Amy R. Baco’s research while affiliated with Florida State University and other places

Cold-water corals (CWC) form reef structures in continental margin and seamount settings at tropical, temperate, and even some polar latitudes. This global distribution makes them more widespread than shallow-water reefs, while their role in these regions is no less important than the influence that shallow-water coral reefs have on shallow, tropical systems. They create habitat structure, host endemic species, enhance elemental cycling, alter current flow, sequester carbon, and provide many other ecosystem services that we are just beginning to understand. This introductory chapter to The Cold-Water Coral Reefs of the World reviews historical and recent information, reveals new findings from reefs that have been discovered only recently, and presents key avenues for future research. Global distribution and environmental data are synthesized into an ensemble model that described the niche of key species of framework-forming corals. Using an algorithm to distinguish coral colony occurrence from coral reef and mound occurrence, we further describe the subset of conditions under which CWC form reefs. This effort reveals new areas that are highly likely to host undiscovered CWC reef habitats and provides a framework for future ocean exploration. We are on the cusp of understanding the critical role that CWC reefs play in the world ocean, and this chapter and this book helps to set the stage for future efforts to determine their global impact and potential threats to the ecosystem services they provide.

The North and Central Pacific are home to a number of major archipelagos including Hawaii, the Marianas, Samoa, Line Islands, Phoenix Islands, and Marshall Islands, and numerous seamounts associated with each of these island groups. These islands span from 14°S, the latitude of American Samoa in the South Pacific, to Kure Atoll at 28°N latitude in the Central North Pacific, with seamounts continuing along the Hawaiian Ridge northwest into the Emperor Seamount Chain. Although all are generally remote, some of these island and seamount chains are so isolated (Hawaii and the Northwestern Hawaiian Islands) that they have some of the world’s highest levels of marine endemism. Differences across the Central Pacific have been documented in the extensive shallow tropical coral reef communities through two decades of directed assessment and monitoring efforts for the subgroup of sites that include the US Pacific Islands. It is likely that deeper coral communities also differ across this region, however, broader explorations of mesophotic and deep-sea communities are needed to document these patterns. Extensive explorations have been undertaken in the Hawaiian Archipelago and started to expand to the rest of the Central Pacific in 2015. Within the North and Central Pacific, deep-sea scleractinian reefs are so far only known to occur from the far end of the Northwestern Hawaiian Islands (NWHI) and lower end of the Emperor Seamount Chain (ESC), and from the Phoenix Islands, thus this chapter will focus on those regions. In all areas of the North and Central Pacific so far explored, dense beds of octocorals and antipatharian corals are instead generally the dominant benthic megafaunal taxa on deep-sea hard substrates, occupying the same functional roles and niche as scleractinian reefs, but far more common and extensively distributed, thus they will also be frequently mentioned.

Marine Areas Beyond National Jurisdiction (ABNJ) are the common heritage of humankind and require coordinated protection, conservation, restoration, and sustainable use by the international community. A common first step in marine area-based management is the identification of Ecologically or Biologically Significant Marine Areas (EBSAs) using the United Nations Convention of Biological Diversity (CBD) scientific criteria. While possessing many EBSA qualities, a published EBSA assessment for the Northwest (NW) Pacific seamounts is lacking. Herein, the CBD EBSA criteria are applied to a seamount complex within ABNJ between the United States (Mariana Islands, Guam, Wake Island Marine National Monument), Federated States of Micronesia, Marshall Islands, and Japan (Ogasawara and Minamitori Island). The EBSA assessment concluded that these Magellan, Marcus-Wake, and Marshall seamounts rank High for all EBSA criteria except one (Medium ranking) and strongly identify these NW Pacific seamounts as an EBSA, including their surrounding water. Existing or anticipated threats to the seamounts include but are not limited to seabed mining and climate change. This NW Pacific Ocean Seamounts EBSA identification synthesizes the best available science and provides a robust assessment and thorough review to support marine area-based management and future CBD workshops on the region.

Marine Areas Beyond National Jurisdiction (ABNJ) are the common heritage of humankind and require coordinated protection, conservation, restoration, and sustainable use by the international community. A common first step in marine area-based management is the identification of Ecologically or Biologically Significant Marine Areas (EBSAs) using the United Nations Convention of Biological Diversity (CBD) scientific criteria. While possessing many EBSA qualities, a published EBSA assessment for the Northwest (NW) Pacific seamounts is lacking. Herein, the CBD EBSA criteria are applied to a seamount complex within ABNJ between the United States (Mariana Islands, Guam, Wake Island Marine National Monument), Federated States of Micronesia, Marshall Islands, and Japan (Ogasawara and Minamitori Island). The EBSA assessment concluded that these Magellan, Marcus-Wake, and Marshall seamounts rank High for all EBSA criteria except one (Medium ranking) and strongly identify these NW Pacific seamounts as an EBSA, including their surrounding water. Existing or anticipated threats to the seamounts include but are not limited to seabed mining and climate change. This NW Pacific Ocean Seamounts EBSA identification synthesizes the best available science and provides a robust assessment and thorough review to support marine area-based management and future CBD workshops on the region.

Management of deep-sea fisheries in areas beyond national jurisdiction by Regional Fisheries Management Organizations/Arrangements (RFMO/As) requires identification of areas with Vulnerable Marine Ecosystems (VMEs). Currently, fisheries data, including trawl and longline bycatch data, are used by many RFMO/As to inform the identification of VMEs. However, the collection of such data creates impacts and there is a need to collect non-invasive data for VME identification and monitoring purposes. Imagery data from scientific surveys satisfies this requirement, but there currently is no established framework for identifying VMEs from images. Thus, the goal of this study was to bring together a large international team to determine current VME assessment protocols and establish preliminary global consensus guidelines for identifying VMEs from images. An initial assessment showed a lack of consistency among RFMO/A regions regarding what is considered a VME indicator taxon, and hence variability in how VMEs might be defined. In certain cases, experts agreed that a VME could be identified from a single image, most often in areas of scleractinian reefs, dense octocoral gardens, multiple VME species’ co-occurrence, and chemosynthetic ecosystems. A decision flow chart is presented that gives practical interpretation of the FAO criteria for single images. To further evaluate steps of the flow chart related to density, data were compiled to assess whether scientists perceived similar density thresholds across regions. The range of observed densities and the density values considered to be VMEs varied considerably by taxon, but in many cases, there was a statistical difference in what experts considered to be a VME compared to images not considered a VME. Further work is required to develop an areal extent index, to include a measure of confidence, and to increase our understanding of what levels of density and diversity correspond to key ecosystem functions for VME indicator taxa. Based on our results, the following recommendations are made: 1. There is a need to establish a global consensus on which taxa are VME indicators. 2. RFMO/As should consider adopting guidelines that use imagery surveys as an alternative (or complement) to using bycatch and trawl surveys for designating VMEs. 3. Imagery surveys should also be included in Impact Assessments. And 4. All industries that impact the seafloor, not just fisheries, should use imagery surveys to detect and identify VMEs.

The deep-sea precious red coral Hemicorallium laauense has long been overharvested in the North Pacific for the jewelry and curio trades. An understanding of the population structure and connectivity of these octocorals has been limited due to the difficulty of sampling and taxonomic challenges within the Family Coralliidae. We report on population genetics of 270 H. laauense individuals from 16 populations throughout the Main Hawaiian Islands (MHI) and the Northwestern Hawaiian Islands (NWHI) using nine microsatellite loci. Observed heterozygosity (0.69–0.85) was generally lower than expected heterozygosity (0.71–0.85) except for the population at Twin Banks. Moderate FIS values (0.01–0.20) were present in nearly half of the populations. Global G’ST (0.166) and pairwise values were moderate to high ( – 0.003 to 0.489). G’ST values also show moderate genetic structuring among populations within seamounts (0.12–0.22) for populations separated by as little as 3 km. DAPC indicated separation of the MHI from the NWHI, but two NWHI sites fall into the MHI clusters and samples from Ka’ena Point (an MHI site) appear to form their own cluster. Membership assignments showed moderate admixture between some locations, while three locations showed almost no admixture. Within-seamount admixture was surprisingly limited for populations on the same seamount. A pattern of isolation by distance, with exchange primarily among adjacent seamounts, was supported by MIGRATE results but not by Mantel tests. These results suggest a mixed pattern of connectivity, with some distant locations well connected and others more isolated. The inconsistent connectivity of these corals is likely amplified by their patchy distributions.

Deep-sea fishes on seamounts have recently been shown to have strong changes in assemblage patterns with depth. However, horizontal variability patterns within a single seamount and among seamounts remain drastically understudied. The Papah¯anaumoku¯akea Marine National Monument (PMNM) is part of an extensive seamount chain that is relatively unimpacted by human activity as well as highly variable in physiographic and oceanographic characteristics. Three PMNM seamounts, Necker Island, French Frigate Shoals (FFS), and Pioneer Bank, were explored using Autonomous Underwater Vehicle surveys to document the deep-sea fish assemblages and their horizontal patterns of distribution at three different depths. Quantitative comparisons were made among the sides of the seamount and among the three seamounts while controlling for depth. The Gadiformes were the most abundant order with the highest number of individuals at 300 and 450 m on Pioneer and FFS. At 600 m the Myctophiformes showed the highest number of individuals overall and were the most abundant on FFS. Significant differences in abundance by seamount, side, and their interaction were observed at 300 and 600 m. Significant differences in some diversity metrics occurred in one, both, or the interaction of the factors of seamount and side at each depth. At all depths, the structure of the fish assemblage showed significant variation among seamounts and sides, which was explained mostly by the interaction term. After accounting for the variability explained by the confounding factor of time of day, the most common environmental factors related to assemblage structure for at least two depths were the east-west component of currents (u), latitude, chlorophyll a (chl a), and particulate organic carbon (POC). At 300 m, oxygen and salinity were also important, at 450 m mean direction of the substrate was an additional factor that was correlated with assemblage structure. At 600 m the factor that explained the most variation in community structure was percent rugosity. The results obtained in this study show significant horizontal variability in seamount fish assemblages within a given depth range; this variability should be taken into consideration in the management and conservation of the Monument and other seamounts.

This annex to the U.S. Pacific Islands chapter in “The State of Deep-Sea Coral and Sponge Ecosystems of the United States” (Parrish et al. 2017) provides a revised and updated list of deep-sea coral taxa in the Phylum Cnidaria, Classes Anthozoa and Hydrozoa, known to occur in U.S. waters around the Hawaiian Archipelago and Johnston Atoll. This list is an update of the peer-reviewed 2017 list, and includes taxa recognized through 2021.