The Northern Sea where seaweed has disappeared - Anomalies off the coast of Oma, Aomori and in the Tsugaru Straits - May 2007

The Northern Sea where seaweed has disappeared - Anomalies off the coast of Oma, Aomori and in the Tsugaru Straits - May 2007

--- (Japanese only)

Anomalies are progressing in the winter sea from the Tsugaru Straits off the coast of Aomori Prefecture to the waters off the coast of Oma. Makombu (kelp) and nori, which would normally thrive during the cold season, have disappeared, seriously affecting the aquaculture industry. In the Tsugaru Straits in particular, seawater temperatures are one to two degrees higher than usual, causing an abnormal proliferation of phytoplankton, resulting in many cases of "color fading" of nori. The decline in the quality of cultured nori has forced fishermen to restrict shipments, dealing a heavy blow to the industry.

Off the coast of Oma, the number of cold current seaweeds has decreased and warm current species have taken their place. The Aomori Prefectural Fisheries Research Center warns of the decline in seaweed and the progression of the "iso-yaki" phenomenon, noting in particular that the seaweed beds of Hondawara and Makombu have shrunk significantly. These changes are related to the long-term upward trend in water temperature in Aomori Prefecture, with the average winter water temperature gradually increasing since the 1990s.

According to a research report by Aomori Prefecture, "Long-Term Fluctuations in Water Temperature and Seaweed Production in the Coastal Areas Surrounding Aomori Prefecture," just one degree Celsius higher water temperature in winter has a significant impact on the growth and distribution of kelp and egonori, and the damage to the local fishing industry and ecosystem is serious. In addition, "Forty Years of Research on Aquaculture in Aomori Prefecture," it is also noted that efforts have been made to observe sea conditions and produce artificial seeds and seedlings of seaweeds in order to cope with such changes.

The ecosystem nurtured by the cold sea is now being shaken. The quiet anomaly off the coast of Oma in the Tsugaru Straits may be a leading indicator of a "sea change" common to all oceans in Japan. In the future, sustainable measures must be developed in terms of aquaculture technology and environmental conservation.

--- (Japanese only)

Related Information
- Long-term fluctuations in water temperature and seaweed production in the coastal areas around Aomori Prefecture" (Aomori Prefectural Industrial Technology Center)
- Aomori Prefectural Research Center for Fisheries Aquaculture, "Forty Years of Research on Aquaculture in Aomori Prefecture" (Aomori Prefectural Industrial Technology Center)
- Aomori Prefectural Fisheries Research Center, 2003 Annual Report of Aomori Prefectural Fisheries Research Center, 2003.