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Summary
The New Zealand marine region has one of the most diverse cold-water coral (CWC) fauna globally, ranging from cosmopolitan framework-building hard coral species to the mostly endemic stylasterid hydrocorals. They are found in depths ranging from shallow coastal waters to several kilometres deep in offshore waters, where they provide habitat to a wide range of marine invertebrates and fish. Most CWC taxa are legally protected in Aotearoa New Zealand and many aspects of their biology, distribution, and threats induced by short- or long-term disturbances are still poorly understood.
In early 2025, the German RV Sonne expedition ‘CoralNewZ’ (SO309) set out to systematically investigate select CWC hotspots off New Zealand and to apply a multi-disciplinary sampling approach to address biological and geological research questions. The main biology objectives of the voyage were to: (i) use high-resolution mapping to identify regional CWC habitats; (ii) use video mapping and faunal sampling to perform a systematic inventory of CWCs and the fauna they are associated with; and (iii) characterise controlling environmental factors by measuring oceanographic parameters and sampling water in the immediate vicinity of CWCs.
Three areas around New Zealand were sampled during the SO309 expedition: (i) the continental shelf break east of Rakiura Stewart Island, including the first detailed observations and sampling of the Rakiura Hills, a group of small guyots and knolls; (ii) the deep (>100 m) Fiordland Marine Area (Te Moana o Atawhenua), including Thompson, Doubtful, Breaksea and Dusky Sound, and the coastal area off Milford Sound; and (iii) the Chatham Rise region (including a repeat survey of four of the previously surveyed features of the Graveyard Knoll complex, and two areas on the top of the Chatham Rise).
In total, 17 Remotely Operated Vehicle (ROV) dives were successfully conducted, a total of 82 hours of bottom time, with 16 dives live streamed to an international audience. A total of 31 Ocean Floor Observation System (OFOS) towed-camera transects were conducted, 29 of which were repeat transects of four knolls in the Graveyard Knoll complex (Morgue, Graveyard, Diabolical and Ghoul), providing an opportunity to build on a 20-year time series of observations in the area. Other gear deployments (13 TV-guided box corers, 25 gravity corers, eight epibenthic sleds (EBS), and 20 CTD casts) were successfully completed and are described in detail in the voyage report provided by Freiwald et al. (2025) but are not covered in further detail here.
The purpose of this technical report is to summarise sampling and preliminary observations during the voyage as relevant to Department of Conservation (DOC) Conservation Services Programme (CSP) contract INT2024-04 (Exploring impacts and recovery potential of protected deep-sea stony corals, utilising Remotely Operated Vehicle capability on RV Sonne in the New Zealand region) and Ministry for Primary Industries (MPI) contract BEN2024-06 (Contribution towards a survey on deep-sea coral biodiversity and environmental drivers around New Zealand). A summary of main voyage activities is provided, focussing on CWC biology, including a detailed description of the observations and sampling conducted using the ROV and OFOS deployments. The ROV enabled fine-scale and high-resolution observations and sampling, particularly of species associations and community assemblages. The OFOS complemented these observations by covering longer distances over the ground and a fixed down-facing camera view, providing comparability to previous studies conducted on long-term coral recovery rates on the Chatham Rise.
We present high-resolution maps and preliminary taxonomic determinations of corals, a species inventory of the 296 samples of Hexacorallia (stony corals and black corals), Octocorallia (gorgonian and soft corals) and Stylasteridae (hydrocorals) from all sampling locations, and commentary on the subsampling (including genetic subsampling, histology and geochemical analyses to be conducted at the German Senckenberg am Meer, MARUM Center for Marine Environmental Sciences and GEOMAR institutes). The taxonomic identification by experts, including the use of molecular taxonomic tools, will be required to confirm species records in the future.
The ability to conduct fine-scale sampling provided the opportunity to collect targeted specimens with which to study the reproduction of New Zealand stony corals. A description of the 24 coral specimens collected and the onboard aquarium is provided. This project is part of a parallel CSP study (POP2024-02: Improving knowledge on coral life history traits, Beaumont and Marriott (2025)).
This report is intended to build on the SO309 voyage report by Freiwald et al. (2025) with detailed descriptions of the samples and observations that will provide resources for ongoing work by New Zealand partners. Scientific highlights of the voyage included first detailed maps and in-situ observations of the Rakiura Hills and their abundant coral communities, exploring the deep basins of the Fiordland region, including a new species of soft coral and potential new records of hard corals for the area. In addition, the detailed ROV survey of extensive coral gardens on Ghoul and Morgue, some of them documented for the first time, and growing evidence supporting the presence of coral mound structures, the first report of such in the SW Pacific, indicate the local persistence of CWC over geological time scales.
Further studies will provide distributional records for regions previously unexplored, evaluate fine-scale observations of the complex CWC communities, and improve our understanding of the damage to and recovery potential of corals from the effects of human impacts such as bottom fishing activities. The data and specimens gathered will, in the future, be used to address many of the identified knowledge gaps on CWC’s in the region including their spatial distribution, biology and ecology, and their resilience to ongoing anthropogenic threats. Furthering our understanding will help inform risk assessments and management plans for these protected deep-sea corals.
Publication information
Schnabel, K., Beaumont, J., Marriott, P., Davidson, S., Holland, L., Beuck, L., Freiwald, A. 2024. Preliminary observations and summary of RV Sonne voyage SO309, 16 January - 15 February 2025. Final report prepared for Project INT2024-04, Conservation Services Programme, Department of Conservation. NIWA Client Report 2025141WN. 133 p.