Diving researches on deep-sea marine ecosystems after Tohoku tsunami

Representative Organization: Japan Agency for Marine-Earth Science and Technology

2015/11/09 - 2015/11/23
7 dives

Off Tohoku
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Research Cruise

To estimate density and influence of the tsunami debris on marine ecosystems, diving researches will be conducted using the newly developed ROV "Crambon" off Miyagi and Iwate. High definition TV images will be taken and biological samples and debris will be collected from the deep sea. In addition, sediment sampling will be conducted using a multiple coring system.

Seven research dives and two test dives were conducted using ROV Crambon at five locations off Sanriku during NT15-E04 cruise from November 9 to 23, 2015. The ROV dive CRB17 was conducted around a depth of 300 m off Minamisanriku for a mapping of benthic organisms, mainly ophiuoroids using a bottom mapping camera system. Total number of 4157 photographs was taken around dense aggregation of ophiuroids. The ROV dive CRB18 was conducted around a depth of 300 m off Ohtsuchi for verifying a large acoustic anomaly (ca. 70 m in length) that was discovered using a sidescan sonar in the previous cruise in March 2015. A large, sunken ship was discovered at a depth of 286 m, where many Pacific cods inhabited. The ship seemed to be sunken far before the Tohoku earthquake because of the shape and condition of the ship. Three dives (CRB19, 20 and 22) were conducted at a base of cliff where assemblage of sunken debris was occasionally reported by fishermen after the earthquake at depths between 400 and 500 m off Sendai Bay. Small assemblage of sunken debris was sparsely discovered but the total amount of the debris was almost the same as that of other locations during these dives. The ROV dive CRB21 was conducted around a depth of 900 m off Kuji for visualizing a massive structure recorded using a PDR by Tohoku National Fisheries Research Institute. A large, sunken ship was discovered at a depth of 882 m, where many rockfish inhabited. The ship seemed to be sunken far before the Tohoku earthquake because of the shape and condition of the ship. Many fishing gears were tangled up with the ship. The ROV dive CRB23 was conducted off Minamisoma at a depth about 300 m to observe the relatively "low fishing-activity" area after the earthquake. Number of Pacific cod seemed larger and the size seemed smaller (younger) than that of the "high fishing-activity" areas. Three-dimensional mosaic mappings of the seafloor were conducted using the stereo camera system.

FY2015 Diving researches on deep-sea marine ecosystems after Tohoku tsunami

NT15-E04_Biological sample data
NATSUSHIMA NT15-E04 Navigation
NATSUSHIMA NT15-E04 Expendable Bathythermograph (XBT)
NATSUSHIMA NT15-E04 Expendable Bathythermograph (XBT) Fall-rate bias corrected
NATSUSHIMA NT15-E04 Sediment Core Sample
NATSUSHIMA NT15-E04 Bathymetry (MBES)
NT15-E04 Crambon Videos
Biological pictures collected from ROV-Crambon movies