Polymetallic nodule mining is a growing commercial interest over the past three decades. It is critical to accurately estimate biodiversity before any minerals are exploited in the Clarion-Clipperton Zone (CCZ) in the Northeast Pacific Ocean. Scavenging amphipods are a large group in the abyssal biota and play an important role in the nutrient cycling system. This study uses both mitochondrial (COI) and nuclear (28S rRNA) DNA markers to investigate genetic diversity and connectivity in Abyssorchomene distinctus (Lysianassoidea – Uristidae) (Birstein & Vinogradov, 1960). The genetic sequences of 113 sampled individuals of Abyssorchomene distinctus, which originated from the CCZ, the Discol Experimental Area (DEA), the Atacama Trench and the Southeast Indian Ridge, revealed the absence of cryptic diversity for A. distinctus on a global scale. The findings contrasted with those for other closely related scavenging amphipods, which revealed the presence of cryptic species. Population genetics analyses calculated a low haplotype diversity (Hd) within the A. distinctus population across the Pacific Ocean, while a high Hd was found in the Indian Ocean populations. This is the first study to date providing preliminary indications of a possible genetic connectivity of the scavenging amphipod species Abyssorchomene distinctus between the CCZ and DEA, being geographically separated by a vast distance of 5,000 km. Shared haplotypes were also found between the CCZ, DEA, Atacama Trench and the Southeast Indian Ridge in the COI mitochondrial DNA dataset , which was congruent with results from previous studies on other scavenging amphipods.
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RBINS Staff Publications 2023
In the wake of the devastating 2011 Tōhoku earthquake and tsunami, the Central Disaster Management Council of the Japanese Cabinet Office issued new guidance for assessing seismic hazards in Japan. Following the unexpectedly large magnitude of the earthquake and the size of the tsunami, the Cabinet Office advocated renewed investigation of earthquake and tsunami occurrence timescales exceeding the historical period, with a particular focus on defining the largest possible magnitudes. The new guidelines pay close attention to the Nankai Trough, the subduction zone where the Philippine Sea Plate dives beneath the Eurasian Plate. The Nankai Trough faces the densely populated and highly industrialised coastline of south central Japan. Here, we review geological evidence for past earthquakes and tsunamis along this subduction zone. This evidence comes from a wide variety of sources, including uplifted marine terraces, turbidites, liquefaction features, subsided marshes and tsunami deposits in coastal lakes and lowlands. More than 70 sites yield evidence, however the number of events recorded at each site varies depending on site-specific evidence creation and preservation thresholds. The longest record exceeds ten thousand years, however the majority are less than four thousand years long. Our compilation suggests that earthquakes in AD 684 and 1361 were similar predecessors of the AD 1707 earthquake, widely regarded as the largest event of the historical period. The more limited distribution of evidence for other historical earthquakes highlights the variability in rupture mode that characterises the Nankai Trough. The palaeoseismic catalogue is, however, limited due to issues over alternative hypotheses for proposed palaeoseismic evidence, poor chronological control and sampling approached insufficient to address the recurrence of the largest past earthquakes and tsunamis. We highlight recent advances and propose future directions for Nankai Trough palaeoseismology.
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