deepccz_benthic Guadalupe Bribiesca-Contreras Life Sciences Department, Natural History Museum

London GB

Thomas Dahlgren University of Gothenburg, Gothenburg, Sweden Norwegian Research Centre, NORCE

Bergen NO

Diva Amon SpeSeas, D’Abadie

TT

Stephen Cairns National Museum of Natural History, Smithsonian Institution

Washington DC US

Regan Drennan Life Sciences Department, Natural History Museum

London GB

Jennifer Durden National Oceanography Centre

Southhampton GB

Marc Eléaume Départment Origines et Évolution, Muséum national d’Histoire Naturelle

Paris FR

Andrew Hosie Collections & Research, Western Australia Museum

Perth AU

Antonina Kremenetskaia Shirshov Institute of Oceanology, Russian Academy of Sciences

Moscow RU

Kirsty McQuaid University of Plymouth

Plymouth GB

Timothy O'Hara Museums Victoria

Melbourne AU

Muriel Rabone Life Sciences Department, Natural History Museum

London GB

Erik Simon-Lledó National Oceanography Centre

Southampton GB

Craig Smith University of Hawai’i at Mānoa

Honolulu US

Les Watling University of Hawai’i at Mānoa

Honolulu US

Helena Wiklund University of Gothenburg

Gothenburg SE

Adrian Glover Life Sciences Department, Natural History Museum

London US

Guadalupe Bribiesca-Contreras Life Sciences Department, Natural History Museum

London GB

2026-07-24 eng There is a growing interest in the exploitation of deep-sea mineral deposits, particularly on the abyssal seafloor of the central Pacific Clarion-Clipperton Zone (CCZ), which is rich in polymetallic nodules. In order to effectively manage potential exploitation activities, a thorough understanding of the biodiversity, community structure, species ranges, connectivity, and ecosystem functions across a range of scales is needed. The benthic megafauna plays an important role in the functioning of deep-sea ecosystems and represents an important component of the biodiversity. While megafaunal surveys using video and still images have provided insight into CCZ biodiversity, the collection of faunal samples is needed to confirm species identifications to accurately estimate species richness and species ranges, but faunal collections are very rarely carried out. Using a Remotely Operated Vehicle, 55 specimens of benthic megafauna were collected from seamounts and abyssal plains in three Areas of Particular Environmental Interest (APEI 1, APEI 4, and APEI 7) at 3100–5100 m depth in the western CCZ. Using both morphological and molecular evidence, 48 different morphotypes belonging to five phyla were found, only nine referrable to known species, and 39 species potentially new to science. This work highlights the need for detailed taxonomic studies incorporating genetic data, not only within the CCZ, but in other bathyal, abyssal, and hadal regions, as representative genetic reference libraries that could facilitate the generation of species inventories. Occurrence GBIF Dataset Type Vocabulary: http://rs.gbif.org/vocabulary/gbif/dataset_type_2015-07-10.xml Observation GBIF Dataset Subtype Vocabulary: http://rs.gbif.org/vocabulary/gbif/dataset_subtype.xml marine, harvested by iOBIS This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License. Creative Commons Attribution 4.0 International https://spdx.org/licenses/CC-BY-4.0.html CC-BY-4.0 Clarion-Clipperton Zone -153.7444 -141.6813 11.2954 4.8875 2018-05-25 2018-06-10 We want to acknowledge the masters, crew and technical support staff on the R/V Kilo Moana and ROV Lu’ukai during the DeepCCZ expedition. We are very grateful for help with taxonomic identifications provided by the expert taxonomists: Estefania Rodriguez (AMNH) for anemones, Dhugal Lindsay (JAMSTEC) for scyphozoans; Chris Mah (NMNH) for sea stars; Rich Mooi (CAS) and Carlos Andres Conejeros Vargas (UNAM) for sea urchins; and Lenka Nealova (NHM) for annelids. We also acknowledge Lauren Hughes (NHM), Miranda Lowe (NHM), Tom White (NHM), Amanda Robinson (NMNH), Emma Sherlock (NHM), Andreia Salvador (NHM), and Andrew Cabrinovic (NHM) for curatorial support; and Elena Luigli (NHM) and Claire Griffin (NHM) for lab support. Primary funding was from the Gordon and Betty Moore Foundation grant no. 5596 and NOAA Office of Ocean Exploration (grant #NA17OAR0110209), and the University of Hawaii. We also acknowledge funding from UK Seabed Resources, the UK Natural Environment Research Council grant numbers NE/T003537/1 and NE/T002913/1 and through National Capability funding to NOC as part of the Climate Linked Atlantic Section Science (CLASS) programme (grant number NE/R015953/1), and The Norwegian Research Council (JPIOMining Impact 2). DJA received funding from the EU’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement number 747946. notPlanned Guadalupe Bribiesca-Contreras Life Sciences Department, Natural History Museum

London GB

After ROV recovery, specimens were transferred and maintained in cold (2–4 °C), filtered seawater until processed. Following Glover et al. (2015), all specimens were photographed, given a preliminary identification and assigned a unique voucher code (e.g., CCZ_020). A tissue sample was taken from each specimen for downstream molecular analyses, and stored in 95% non-denatured ethanol at -20 °C. Specimens were fixed in 10% borax-buffered formalin and transferred to 70% non-denatured ethanol after 48 h, except for sponges, which were kept frozen at -80 °C. After the expedition, specimens and tissue sub-samples were sent to the University of Hawai’i Manoa. Specimens were archived at the Natural History Museum, London (NHMUK), and the Western Australian Museum (WAM), following taxonomic inspection. Clarion-Clipperton Zone Specimens were selected from across as many taxonomic groups as possible, with duplicates of similar morphotypes avoided; thus, the aim was to increase our understanding of megafaunal diversity. A total of 55 specimens were collected during different dives in three APEIs and three different geoforms (abyssal plain, seamount, and seamount slope), 14 specimens were collected from abyssal seafloor in APEI 1; 13 from abyssal seafloor, two from the seamount slope and six from a seamount in APEI 4; and nine from abyssal seafloor and 11 from a seamount in APEI 7. In situ photographs and/or video frame grabs of each specimen were captured, with parallel lasers for scale at 15 cm spacing. Megafaunal specimens were collected with the manipulator (‘Orion’), suction sampler, or push cores, depending on the characteristics of each specimen in order to best preserve morphological characters. Specimens collected with the manipulator were placed into the biobox receptacle, while those collected with the suction sampler were stored in a suction box. Collection data were recorded at the time of capture (e.g., date and time, ROV latitude/longitude, seabed water depth, ROV waypoint name). 2026-07-24T15:50:50.916+12:00 dataset Bribiesca-Contreras G, Dahlgren T, Amon D, Cairns S, Drennan R, Durden J, Eléaume M, Hosie A, Kremenetskaia A, McQuaid K, O'Hara T, Rabone M, Simon-Lledó E, Smith C, Watling L, Wiklund H, Glover A (2026). Benthic megafauna of the western Clarion-Clipperton Zone, Pacific Ocean from the DeepCCZ project, 2018. Version 1.0. Southwestern Pacific Ocean Biogeographic Information System (OBIS) Node. Occurrence dataset. https://nzobisipt.niwa.co.nz/resource?r=deepccz_benthic&v=1.0 Bribiesca-Contreras G, Dahlgren TG, Amon DJ et al. Benthic megafauna of the western Clarion-Clipperton Zone, Pacific Ocean. ZooKeys 2022;1113:1–110. 10.3897/zookeys.1113.82172