Development of a multibottle gas‐tight fluid sampler WHATS II for Japanese submersibles/ROVs

Abstract

This paper summarizes the design and performance of our recently developed gas-tight fluid sampler WHATS II, especially designed to collect seafloor venting gas-rich fluid from submersibles/remotely operated vehicles (ROVs). It consists of four 150-cm 3 stainless steel sample cylinders, eight ball valves, a motor-driven arm, a rail, a peristaltic pump, a control unit, and a flexible Teflon tube connected to a titanium inlet tube. All the parts have been designed to be used at undersea as deep as 4000 m. The motor-driven arm on the rail can open and close each of the four cylinders. By pumping out distilled water that has filled an open cylinder and the dead spaces of the sampler, we can fill the cylinder with sample fluid. WHATS II can take a maximum of four different gas-tight samples in a series. The whole operation can be arranged from the cabin, etc., of a submersible/ROV. Use of only one motor to operate eight valves makes the sampler small, light (21 kg in sea water), and easy to handle. In addition, the sampler is able to collect an almost uncontaminated gas-tight sample from the seafloor. To date, the sampler has been used in more than 90 dive surveys by Japanese submersibles/ROVs, including Shinkai 2000, Shinkai 6500, and Hyper Dolphin, with a success rate of >90%.

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

“…The Okinawa Trough is a backarc basin in the rifting to spreading stage characterized by the development of normal faulting of transitional crust (atypical crust with mantle-derived material) and frequent magma intrusions, which provides a favorable geological environment for the development of seafloor hydrothermal systems [8,41,42]. As of 2016, there were at least 15 deep-sea hydrothermal fields reported in the Okinawa Trough based on the InterRidge data base, including the Minami-Ensei (e.g., [10]), Iheya North [9,11,43], Jade [7,13], Hakurei [8], Hatoma [44][45][46], Yonaguni Knoll IV [12,14,47], and Tangyin hydrothermal fields [48,49]. The Iheya North knoll hydrothermal field (27 ∘ 47.2 N, 126 ∘ 53.9 E) is located at a water depth about 1,000 m along the eastern slope of a small knoll, part of the Iheya North knoll volcanic complex ( Figure 1; [8]).…”

Origin and fate of deep-sea seeping methane bubbles at Kuroshima Knoll, Ryukyu forearc region, Japan

“…In dives for sampling bottom fluid, a titanium inlet tube was used for the sample inlet, while a specially designed funnel-shaped inlet was used for sampling gas bubbles (Saegusa et al, 2006). Because we could not recognize fluid seeping from Kuroshima Knoll, we took seawater less than 30 cm above the seafloor, in areas where active fluid seeping was anticipated, such as areas covered by dense Bathymodiolus mussels.…”

“…Gas bubbles and bottom fluid (seawater taken just above the seafloor of the gas seepage site) were collected by the human occupied vehicle Shinkai 2000 of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) during the NT02-08 cruise in June 2002, using the WHATS Saegusa et al, 2006). The sampler comprised four 150 cm 3 stainless steel sample cylinders, eight ball valves, a motor-driven arm, a rail, a peristaltic pump, and a flexible Teflon tube connected to the inlet.…”

“…The detailed bottom topography in the square (the area around Kuroshima Knoll) is presented in Fig. 2. Sampler) Saegusa et al, 2006) attached to the vehicle Shinkai 2000 to determine the origin of CH 4 and discuss the possible sub-seafloor dissociation of methane hydrate using geochemical tracers. Knowledge of the origin of CH 4 (i.e., biogenic from acetate fermentation or CO 2 reduction, thermogenic, inorganic) and the other coexisting gases would provide information on the processes and environments responsible for their generation.…”

Post‐drilling changes in fluid discharge pattern, mineral deposition, and fluid chemistry in the Iheya North hydrothermal field, Okinawa Trough

“…On September 20, 1 week after drilling at Hole C0013E but before Site C0016 was drilled, Chikyu departed from the Iheya North field for 2 days, and during this period, the ROV Hyper Dolphin approached Site C0013 and the NBC mound during an NT10-17 cruise by R/V Natsushima. In addition, R/V Kaiyo (KY) and/or Natsushima ( [9] The hydrothermal fluid samples were collected using a gas-tight sampler (WHATS) [Saegusa et al, 2006] and vacuum samplers . WHATS includes a $3 m length inlet tube connected through a manifold to four 150 mL stainless-steel bottles followed by a peristaltic pump with an overflow fluid waste vent.…”