Spatial variability in recruitment of benthos near drilling sites in the Iheya North hydrothermal field in the Okinawa Trough

Due to increasing anthropogenic impacts on deep-sea hydrothermal vent ecosystems, it is essential to understand population structure and maintenance through larval recruitment and recovery of vent faunas after disturbances. In this study, we quantified vent animal recruitment in the Okinawa Trough, in the western Pacific Ocean. This is the first study to investigate recruitment patterns at a man-made hydrothermal vent. Colonization plates were deployed at three sites. Site 1 manifested new hydrothermal shimmering with small chimneys, white bacterial mats, and some alvinocaridid shrimp that arrived after drilling. Site 2 showed no evidence of newly arrived foundation species after drilling, and Site 3 had pre-existing animal communities in the vicinity of the new vent. Twenty-two months after deployment, colonization plates were retrieved and recruited animals were inventoried. Species composition and abundance differed among sites, but relatively high similarity in species composition was observed at Sites 1 and 3, though not at Site 2. Newly established communities on the plates at Sites 1 and 2 (no pre-existing fauna) showed lower species richness and abundance than at Site 3. Differences in abundance and size-frequency distributions of major recruits on the plates (i.e. Lepetodrilus mix, Bathymodiolus spp.) suggest the importance of reproductive and early life-history characteristics in spatial variability of recruitment. Lepetodrilus mix populations established on the plates at Site 1 showed high genetic connectivity. These results illustrate the importance of localized recruitment, which may have a significant impact on sustainability of vent faunal populations, despite the existence of regional metapopulations

Digital In-Line Holography for Large-Volume Analysis of Vertical Motion of Microscale Marine Plankton and Other Particles

Acknowledgements This work is funded by a joint UK-Japan research program (NERC-JST SICORP Marine Sensor Proof of Concept under project code NE/R01227X/1). The authors would like to thank the captain, crew, science party and technical support staff of the R/V Yokosuka cruise YK20-E02. We also thank Dr. Y. Nagai for providing us the foraminifera samples.Peer reviewedPostprin

Species assemblage networks identify regional connectivity pathways among hydrothermal vents in the Northwest Pacific

The distribution of species among spatially isolated habitat patches supports regional biodiversity and stability, so understanding the underlying processes and structure is a key target of conservation. Although multivariate statistics can infer the connectivity processes driving species distribution, such as dispersal and habitat suitability, they rarely explore the structure. Methods from graph theory, applied to distribution data, give insights into both connectivity pathways and processes by intuitively formatting the data as a network of habitat patches. We apply these methods to empirical data from the hydrothermal vent habitats of the Northwest Pacific. Hydrothermal vents are “oases” of biological productivity and endemicity on the seafloor that are imminently threatened by anthropogenic disturbances with unknown consequences to biodiversity. Here, we describe the structure of species assemblage networks at hydrothermal vents, how local and regional parameters affect their structure, and the implications for conservation. Two complementary networks were formed from an extensive species assemblage dataset: a similarity network of vent site nodes linked by weighted edges based on their pairwise assemblage similarity and a bipartite network of species nodes linked to vent site nodes at which they are present. Using these networks, we assessed the role of individual vent sites in maintaining network connectivity and identified biogeographic sub-regions. The three sub-regions and two outlying sites are separated by their spatial arrangement and local environmental filters. Both networks detected vent sites that play a disproportionately important role in regional pathways, while the bipartite network also identified key vent sites maintaining the distinct species assemblages of their sub-regions. These regional connectivity pathways provide insights into historical colonization routes, while sub-regional connectivity pathways are of value when selecting sites for conservation and/or estimating the multivent impacts from proposed deep-sea mining

Population history of deep-sea vent and seep Provanna snails (Mollusca: Abyssochrysoidea) in the northwestern Pacific

Background Gastropods of the genus Provanna are abundant and widely distributed in deep-sea chemosynthetic environments with seven extant species described in the northwestern Pacific. Methods We investigated the population history and connectivity of five Provanna species in the northwestern Pacific through population genetic analyses using partial sequences of the cytochrome c oxidase subunit I gene. Results We found that P. subglabra, the most abundant and genetically diverse species, is genetically segregated by depth. Among the five species, the three comparatively shallower species (P. lucida, P. kuroshimensis, P. glabra) had a more constant demographic history compared to the deeper species (P. subglabra, P.  clathrata). Discussion Environmental differences, especially depth, appears to have a role in the segregation of Provanna snails. The population of P. clathrata in the Irabu Knoll appears to have expanded after P. subglabra population. The remaining three species, P. lucida, P. kuroshimensis, and P. glabra, are only known from a single site each, all of which were shallower than 1,000 m. These data indicate that Provanna gastropods are vertically segregated, and that their population characteristics likely depend on hydrothermal activities

Isolation and characterization of novel polymorphic microsatellite loci for the deep-sea hydrothermal vent limpet, Lepetodrilus nux, and the vent-associated squat lobster, Shinkaia crosnieri

Recent genetic research has begun to reveal population structures of deep-sea, hydrothermal vent species, but detailed assessments of genetic diversity and connectivity in hydrothermal vent populations, based on multiple genetic loci, are still scarce, especially in the Northwest Pacific. Accordingly, we isolated 38 novel polymorphic microsatellite loci from the limpet, Lepetodrilus nux, and 14 from the squat lobster, Shinkaia crosnieri, two dominant hydrothermal vent species, using next-generation sequencing. These loci revealed polymorphism levels of 5–20 alleles per locus in L. nux and 5–25 in S. crosnieri. Observed and expected heterozygosities ranged from 0.240 to 0.960 and 0.283 to 0.938 in L. nux and from 0.450 to 0.950 and 0.620 to 0.941 in S. crosnieri, respectively. Twelve loci in L. nux and four loci in S. crosnieri showed significant deviation from Hardy–Weinberg equilibrium (p < 0.05). Microsatellite loci evaluated in this study will enable detailed measurements of genetic diversity and connectivity among populations, and better understanding of evolutionary divergence processes of L. nux and S. crosnieri in deep-sea communities in the Northwest Pacific

A blueprint for an inclusive, global deep-sea Ocean Decade field programme

The ocean plays a crucial role in the functioning of the Earth System and in the provision of vital goods and services. The United Nations (UN) declared 2021–2030 as the UN Decade of Ocean Science for Sustainable Development. The Roadmap for the Ocean Decade aims to achieve six critical societal outcomes (SOs) by 2030, through the pursuit of four objectives (Os). It specifically recognizes the scarcity of biological data for deep-sea biomes, and challenges the global scientific community to conduct research to advance understanding of deep-sea ecosystems to inform sustainable management. In this paper, we map four key scientific questions identified by the academic community to the Ocean Decade SOs: (i) What is the diversity of life in the deep ocean? (ii) How are populations and habitats connected? (iii) What is the role of living organisms in ecosystem function and service provision? and (iv) How do species, communities, and ecosystems respond to disturbance? We then consider the design of a global-scale program to address these questions by reviewing key drivers of ecological pattern and process. We recommend using the following criteria to stratify a global survey design: biogeographic region, depth, horizontal distance, substrate type, high and low climate hazard, fished/unfished, near/far from sources of pollution, licensed/protected from industry activities. We consider both spatial and temporal surveys, and emphasize new biological data collection that prioritizes southern and polar latitudes, deeper (&gt; 2000 m) depths, and midwater environments. We provide guidance on observational, experimental, and monitoring needs for different benthic and pelagic ecosystems. We then review recent efforts to standardize biological data and specimen collection and archiving, making “sampling design to knowledge application” recommendations in the context of a new global program. We also review and comment on needs, and recommend actions, to develop capacity in deep-sea research; and the role of inclusivity - from accessing indigenous and local knowledge to the sharing of technologies - as part of such a global program. We discuss the concept of a new global deep-sea biological research program ‘Challenger 150,’ highlighting what it could deliver for the Ocean Decade and UN Sustainable Development Goal 14

Two new species of the crangonid genus Metacrangon Zarenkov, 1965 (Crustacea: Decapoda: Caridea) from the Okinawa Trough, Japan

Two new species of the crangonid shrimp genus Metacrangon Zarenkov, 1965, are described and illustrated on the basis of materials collected from the Okinawa Trough, Ryukyu Islands, southern Japan, during diving operations of remotely operated vehicles (ROVs): M. ryukyu n. sp. from off Iheya Island, at depth of 986 m; and Metacrangon kaiko n. sp. from NE of Yonaguni Island, at depth of 2205 m. The two new species resemble members of the M. munita (Dana, 1852) species group, but are both characteristic in having setose dactyli on pereopods 4 and 5. Some minor differences in morphology and genetic analysis using partial sequences of the barcoding mitochondrial COI gene support the recognition of the two new species. Holotypes of the two new species were collected from hydrothermally influenced areas, representing a previously unknown habitat for species of Metacrangon

First columbellid species (Gastropoda: Buccinoidea) from deep-sea hydrothermal vents, discovered in Okinawa Trough, Japan

Chen, Chong, Watanabe, Hiromi Kayama, Araya, Juan Francisco (2017): First columbellid species (Gastropoda: Buccinoidea) from deep-sea hydrothermal vents, discovered in Okinawa Trough, Japan. Zootaxa 4363 (4): 592-596, DOI: https://doi.org/10.11646/zootaxa.4363.4.1

Unanticipated discovery of two rare gastropod molluscs from recently located hydrothermally influenced areas in the Okinawa Trough

Background The deep-sea hydrothermal vent is one of the most ‘extreme’ environments in the marine realm. Few species are capable of inhabiting such ecosystems, despite extremely high productivity there supported by microbial chemosynthesis, leading to high biomass and low species richness. Although gastropod molluscs are one of the main constituents of megafaunal communities at vent ecosystems, most species belong to several typical families (e.g., Provannidae, Peltospiridae, Lepetodrilidae) specialised and adapted to life at vents. Methods During recent surveys of Okinawa Trough hydrothermal vent systems, two snails atypical of vent ecosystems were unexpectedly found in newly discovered hydrothermally influenced areas. Shell and radular characteristics were used to identify the gastropods morphologically. Results One species was a vetigastropod, the calliostomatid Tristichotrochus ikukoae (Sakurai, 1994); and the other was a caenogastropod, the muricid Abyssotrophon soyoae (Okutani, 1959). Both gastropods were previously only known from regular non-chemosynthetic deep-sea and very rare—only two definitive published records exist for T. ikukoae and three for A. soyoae. The radula formula of Tristichotrochus ikukoae is accurately reported for the first time and based on that it is returned to genus Otukaia. For both species, barcode sequences of the cytochrome c oxidase I (COI) gene were obtained and deposited for future references. Discussion These new records represent the second record of calliostomatids from vents (third from chemosynthetic ecosystems) and the third record of muricids from vents (tenth from chemosynthetic ecosystems), and extend the distribution of both species to the southwest. Neither family has been recorded at chemosynthetic ecosystems in the western Pacific. Both were from weakly diffuse flow areas not subject to high temperature venting but were nevertheless associated with typical vent-reliant taxa such as Lamellibrachia tubeworms and Bathymodiolus mussels. These new records show that these species are capable of tolerating environmental stress associated with weak hydrothermally influenced areas, despite not being vent endemic species, adding to the list of known vent/non-vent species intersections. This signifies that such weakly influenced areas may provide key habitats for them, and that such areas may play a role in the evolution of biological adaptations to ‘extreme’ chemosynthetic ecosystems