Press Release

September 12, 2012

Incorporated Administrative Agency, Fisheries Research Agency

Oxygen deficient water masses were simultaneously monitored throughout the Ariake Sea

  • Simultaneous monitoring revealed that large-scale oxygen deficient water masses were formed mainly at the inner part of the Ariake Sea, and Isahaya Bay; thus, oxygen-deficient area was roughly estimated

Oxygen deficient water masses and red tides, which are caused by proliferation of toxic phytoplankton, have been frequently observed in the Ariake Sea in recent years, causing serious damage to fisheries as well as to the entire ecosystem.

To investigate the generation mechanisms of oxygen deficient water masses causing deterioration of the fishing grounds in the Ariake Sea, and their impact on fishery resources, the simultaneous monitoring was conducted at 200 fixed observation points on August 10, jointly by 17 institutes including the Seikai National Fisheries Research Institute, the national and prefectural governments, universities, and private companies.

This and two preceding monitoring surveys revealed that oxygen deficient water masses in the interior of the Ariake Sea were formed in relatively shallow layer (5~15 m) and that another large-scale oxygen deficient water mass was also formed in Isahaya Bay. The conditions and scales of oxygen deficiency monitored this time were similar to those of the past; hence, the data helped us to identify the approximate zones of oxygen deficient water formation and understand the precise oceanic environments (see the reference).

Continuation of this kind of monitoring survey is expected to be useful in comprehending not only distribution of oxygen deficient water masses but also low-salt content water masses, primary productivity, decomposition of organic matters, transport and settling of clam larvae, etc. and to decrease fisheries damages.