Japan Geoscience Union Meeting 2023

Presentation information

[J] Online Poster

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS18] Gas hydrates in environmental-resource sciences

Tue. May 23, 2023 10:45 AM - 12:15 PM Online Poster Zoom Room (21) (Online Poster)

convener:Hitoshi Tomaru(Department of Earth Sciences, Chiba University), Shinsuke Aoki(The National Institute of Advanced Science and Technology)

On-site poster schedule(2023/5/22 17:15-18:45)

10:45 AM - 12:15 PM

[MIS18-P05] Preliminary Study on the Capture, Rearing, and Biological Impact of a Deep-Sea Amphipod (Lysianassoidea) in the Sea of Japan

*Hiroshi Ishida1, Eriko Seo1, Megumi Yamamoto1, Ryo Mukai2, Eri Ikeuchi3, Hiroki Kise3, Miyuki Nishijima3, Akira Iguchi3, Atsushi Suzuki3, Masahiro Suzumura4 (1.The Marine Ecology Research Institute , 2.Marine Biological Research Institute of Japan Co., Ltd., 3.Research Institute of Geology and Geoinformation, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, 4.Environmental Management Research Institute, National Institute of Advanced Industrial Science and Technology)

Keywords:Deep-sea amphipods, Shallow methane hydrate, Sea of Japan, Biological impact experiments

The deep-sea floor around Japan has large quantities of methane hydrate. Technologies to assess this resource and its environmental impact are under investigation. Here, a genetic analysis of inhabiting organisms and an assessment of amphipod biodiversity and connectivity were conducted.
Amphipods play an essential role in the oceanic carbon cycle as they pulverize and convert organic matter into labile components, which bacteria and other microorganisms can efficiently utilize. In the deep-sea waters of Japan, amphipods serve as prey as well as competitors in feeding for beneficial crustaceans such as the red snow crab (Chionoecetes japonicus). Therefore, amphipods are important target organisms for environmental impact assessments in developing marine resources.
In this study, for the development of environmental impact assessment technology for shallow methane hydrate in the Sea of Japan, the same species of amphipods were captured in a viable state from the seafloor at a depth of approximately 1,000 m. We utilized bait traps to capture living amphipods along with the in situ seawater. The captured amphipods were immediately transferred to a seawater tank on board at a temperature of 1–2°C without exposure to the atmosphere and were found to remain active. A refrigerated courier service transported amphipods from the vessel to the rearing research facility. The amphipods were identified as Pseudorchomene sp. based on morphological observations and genetic analysis.
We selected 44 individuals approximately 10 mm in length, placed them in glass bottles, and refrigerated them at 0°C. We fed horse mackerel at approximately 20-day intervals. Five individuals survived for one year after the start of rearing, with one individual surviving 467 days, bringing the total number of exuviae to 78. The exuviation interval was approximately 90 days, suggesting that exuviation failure and predation on exuding individuals are closely related to population depletion.
The biological impacts of water temperature, low salinity, and hydrogen sulfide content on amphipods were assessed. Amphipods continued to survive in water below 10 °C, died within 48 h at 15°C, and died immediately at 20°C. The 96 h lethal concentration 50 (LC50 - 96h) for low salinity was estimated to be 18.9 PSU (95% confidence limit: 19.6–18.1 PSU). The LC50 - 96h for hydrogen sulfide was higher than the reported values for beneficial marine crustaceans and coastal amphipods (Melita sp.).
This study was conducted as part of the Methane Hydrate Research Project of the Ministry of Economy, Trade and Industry.