Press Releases

Press Releases

Figure 1. Map of study area
a: Position of the Mariana Trench and Challenger Deep; b: Surveyed sites.
A total of 4 samplings were made at the Challenger Deep site, and 3 at the abyssal plain site.

Figure 2. The 2 free-fall landers and auxiliary equipment used for the project
a: The free-fall lander developed jointly by the University of Southern Denmark, Scottish Association for Marine Science, and Max Planck Institute for Marine Microbiology, and reinforced by JAMSTEC to withstand high pressure. A variety of equipment is attached to the aluminum frame, including flotation buoys, weights, an acoustic release, and sensors. The lander is deployed from the vessel and measurements taken by the sensors after it reaches the seabed. After measurements have been made, an acoustic signal sent from the vessel is picked up by the acoustic release, causing the weights to be released. The lander becomes buoyant as a result, rising to the surface to be recovered by the vessel.
b: The ultrathin oxygen sensor unit attached to the lander shown in a. The unit measures the vertical distribution of oxygen in seabed sediment when the oxygen sensors, which are no more than several dozen micrometers in width (about the width of a needle tip) at their tips, are inserted 0.5–1.0 mm at a time into the seabed by using a high-precision motor so as not to disturb the sediment environment. Once measurements have been taken, the sensors are raised and the unit is moved horizontally to take further measurements in a slightly different location.
c. The free-fall lander developed by JAMSTEC equipped with a sediment sampling system and video camera. It is operated by using the same methods as those for the lander shown in a. The lights are switched on to allow video filming. The sediment corers on the legs contain collected sediment samples.
d: Some of the flotation buoys used for both free-fall landers. They are made from a special resin that contains microscopic glass spheres to ensure that they can even withstand the high-pressure environment at water depths greater than 10,000 m.

Figure 3. The seabed as filmed by the camera of the sediment sampling system.
a: At the abyssal plain site (water depth 6032 m) and b: the Challenger Deep site (water depth 10, 900 m). Benthic organisms and mound-like structures presumably created by them were observed on the seabed of the abyssal plain site. Fish species and other larger fauna were also seen. No structures created by benthic organisms were seen on the seabed of the Challenger Deep, although faint ripple marks caused by currents were visible. No fish or other larger species were found at this depth, although the amphipod species Hirondellea gigas, holothurians, and other smaller creatures were visible, albeit in sparse numbers.

Figure 4. Vertical distribution of oxygen concentration in the seabed of a: the abyssal plain site (water depth of 6018 m) and b: the Challenger Deep site (water depth of 10, 817 m). Oxygen decline in the sediment of the abyssal plain site is slight compared with that of the Challenger Deep site. This suggests that in the sediment of the Challenger Deep site, oxygen consumption is higher, and therefore, that aerobic decomposition of organic carbon is highly active.

Figure 5. a, b: organic carbon concentration; c, d: chlorophyll a and pheophytin concentrations; e, f: density of microbes (prokaryotes). a, c, and e show the analysis results of the abyssal plain site sediment, and b, d, and f those of the Challenger Deep site sediment.