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Offshore Seafloor 313 Nankai Trough from Suruga bay to Kyushu waters

Basic Information A separate window opensReferences

Area (km2) 105431
Maximum water depth (m) 4907

Reason(s) for selection A separate window opensCriteria

Selected due to high levels for criteria 1, 4, 5, 6, and 8, and selected by MARXAN software.

Characteristics A separate window opensReferences

These waters extend from the east side of Suruga Bay to the Nankai Trough, which drops sharply from the coast all the way to southern Kyushu. Waters that deepen suddenly extend from the coast of Cape Omaezaki to the Kii Peninsula (to the south of Cape Ashizuri), reaching a difference in elevation of 1800 m and a total length of 670 km (Tokuyama et al, 2001). It includes many submarine short canyons (Japan Coast Guard, Hydrographic and Oceanographic Department, 1985).
The V-shaped submarine canyon with depths of 2000 m that runs through the middle of Suruga Bay (the Suruga Trough) separates the Eurasia Plate to the north from the Philippine Sea Plate to the south. On the east side of these waters is a bank called Senoumi where Calyptogena kawamurai have been discovered, suggesting the presence of a community of chemotrophs (Fujikura et al, 2008).
As a boundary between plates, the Nankai Trough is predicted to be the epicenter of a massive earthquake. These waters have been confirmed to be home to the greatest number of seep communities, and here from Kinsunose (off Cape Omaezaki to the south) to the waters 4800 m deep offshore from the coast of Cape Muroto, seep communities have been discovered in numbers unrivaled worldwide. Also here are highly diverse species of bivalves in the family Vesicomyidae, with at least 12 species discovered thus far. At Kinshunose, Mesolinga soliditesta, Bathymodiolus aduloides, and others have been discovered, leading to speculation that there are active methane seeps here. The presence of a bottom simulating reflector (BSR) has been confirmed in this area as well, and it is thought that there is a methane hydrate layer here (Fujikura et al., 2008).
In the Tenryu Canyon that cuts across the Nankai Trough, diverse species have been reported, including not only those specific to seep communities but also many species that depend on photosynthesis, and invasive species as well. The Kumano Basin in the southern Kumano Sea is home to seven mud volcanoes. BSRs have been confirmed in the seabottom called Kumano Knolls Nos. 1-7 as well, and these waters are habitat for Calyptogena fausta, Vesicomya crenulomarginata, Calyptogena (Archivesica) similaris, and others. Seep communities are found at Muroto Knoll off Cape Muroto as well, and Vesicomya kaikoae are distributed here. Species of tubeworm have been confirmed at Ashizuri Knoll of Cape Ashizuri (Fujikura et al, 2008).
Numerous species of precious corals are distributed offshore from Cape Ashizuri and Cape Muroto (Iwasaki, 2008), making this a coral fishing grounds. The waters of the Kumano Sea and off the shore of Tosa are high in biodiversity in terms of fish species as well (Kimura, personal communication).

Environment / Habitat information A separate window opensData source

Chemosynthetic community, Seamount, Canyon

Species information (*) A separate window opensData source

Criteria 1
Scymnodon ichiharai (Japanese Velvet Dogfish)
Lycodes caudimaculatus
Paraliparis atramentatus
Oxynotus japonicus (Japanese Roughshark)
Melanostigma orientale
Zesticelus bathybius
Pseudonezumia cetonuropsis
Careproctus rhodomelas
Bassozetus zenkevitchi
Trigonognathus kabeyai (Viper Dogfish)
    Acabaria modesta
    Anthomastus japonicus
    Eunicella pendula
    Melithaea flabellifera
    Minabea ozakii
    Paragorgia regalis
    Pennatula brevipenna
    Pennatula inermis
    Pennatula naresi
    Plumarella flabellata
    Plumarella lata
    Thouarella recta
    Villogorgia japonica
<Other invertebrate>
Phoxichilidium ungellatum
Synhalcurias elegans
Pycnogonum tenue
Criteria 4
Centrophorus squamosus (Leafscale Gulper Shark)
    Acabaria modesta
    Acabaria ramurosa
    Acalycigorgia densiflora
    Acalycigorgia inermis
    Acalycigorgia irregularis
    Acalycigorgia radians
    Acanella sibogae
    Acanthogorgia multispina
    Acanthoprimnoa cristata
    Anthogorgia bocki
    Anthomastus granulosus
    Anthomastus japonicus
    Anthomuricea brunnea
    Anthoptilum murrayi
    Arthrogorgia ijimai
    Calcigorgia beringi
    Calicogorgia granulosa
    Chromonephthea serratospiculata
    Chrysogorgia lata
    Corallium japonica
    Echinogorgia regularis
    Echinogorgia ridleyi
    Ellisella plexauroides
    Ellisella rubra
    Eunicella pendula
    Euplexaura anastomosans
    Euplexaura curvata
    Helicoptilum rigidum
    Heterogorgia papillosa
    Junceella juncea
    Kophobelemnon hispidum
    Melithaea flabellifera
    Menella lenzii
    Menella praelonga
    Menella spinifera
    Minabea ozakii
    Nidalia rigida
    Paragorgia regalis
    Pennatula brevipenna
    Pennatula fimbriata
    Pennatula inermis
    Pennatula naresi
    Pennatula sanguinea
    Plumarella flabellata
    Plumarella lata
    Radicipes pleurocristatus
    Sarcophyton acutangulum
    Siphonogorgia splendens
    Solenocaulon chinense
    Subergorgia thomsoni
    Telesto aurantiaca
    Thouarella alternata
    Thouarella hilgendorfi
    Thouarella recta
    Trichoptilum spinosum
    Umbellula eloisa
    Umbellula magniflora
    Verrucella miniacea
    Verrucella umbella
    Verrucella umbraculum
    Villogorgia japonica

* This is the species list of which meet the criteria. In that matter, this list does not include all species that inhabit the individual area.


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