Application of SeaXerocks on habitat mapping for the deep-sea megabenthos around cobalt-rich ferromanganese crusts in Arnold Guyot of the northwestern Pacific - from the perspective of "whale's eye view"

Iguchi, A., Miwa, R., Koike, T., Ohhara, M., Sugishima, H., Yokooka, H., Fukuhara, T., Suzumura, M., Tsukasaki, A., Tanaka, Y., Iwasaki, N., Thornton, B., Fujii, T., Kato, S., Igarashi, Y., Okamoto, N. and Suzuki, A. (2019) Application of SeaXerocks on habitat mapping for the deep-sea megabenthos around cobalt-rich ferromanganese crusts in Arnold Guyot of the northwestern Pacific - from the perspective of "whale's eye view". American Geophysical Union, Fall Meeting 2019,, , San Francisco, United States. 09 - 13 Dec 2019.

Abstract

In this study, to improve image acquisitions in the deep-sea environments, we performed habitat mapping by visualizing distribution patterns of benthic organisms and environments around cobalt-rich ferromanganese crusts by using a state-of-the-art 3-D mapping device SeaXerocks system. We applied SeaXerocks mounted on the skid of an underwater remotely operated vehicle (ROV) along a survey line (about 1.4 km) on the flat top of the Arnold Guyot in the International Seabed Authority (ISA) licensed exploration area for Japan in the northwestern Pacific. As the result, we succeeded in grasping the distributions of microtopography and benthic organisms based on whale's eye view of the sea floor of ~1,400 m depth. The distributions of sessile organisms such as Porifera and Gorgonacea were aggregated on the surface of hard substrates as expected, indicating bottom conditions restrict the distribution of megabenthos. Our observation also clarified the pattern of sand ripples suggesting the direction of dominant bottom water current from northeast to southwest or vice versa. The SeaXerocks system enables us to grasp the relationship between distribution of organisms and environmental factors in more details than the previous methods. Knowledge of these patterns is essential not only for understanding biodiversity patterns but also for the selection of possible mining sites and preservation reference zones, which are required by the ISA environmental guidelines. Thus, the application of SeaXerocks would contribute to the environmental baseline studies and impact assessments relating to future deep-sea mining activities.

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