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The coastline off Seogwipo, Jeju Island

Jeju Island is urgently working with related agencies to develop countermeasures for the growing possibility of low-salinity water from China entering the surrounding sea.

Jeju Island announced on Aug. 2 that it had recently held a meeting of its “emergency countermeasures council for a response to Yangtze River flooding from China” to discuss the possibility of low-salinity water arriving from China and a step-by-step response to its impact. The island has established a dedicated response system with the Ministry of Oceans and Fisheries (MOF), the National Institute of Fisheries Science (NIFS), and the Korea Institute of Ocean Science & Technology (KIOST) to predict the movements of low-salinity water in the East China Sea.

According to the island’s analysis, heavy rains in southern China since mid-June have resulted in the Yangtze River’s outflows increasing by 44% over ordinary years. On July 12, the river recorded an outflow of 83,200 tons per second; on July 26, another was recorded at over 70,000 tons. The scale was the largest outflow from the Yangtze to be observed since 2003 by the Jeju Self-Governing Province Oceans and Fisheries Institute.

It is also larger than the outflow of 66,700 tons observed in 2016, when fish, shellfish, and other marine resources died off en masse due to inflows of low-salinity water along the Jeju coast. As water discharged from the Yangtze mixes with sea water to cause low saline concentrations of less than 30 psu (practical salinity units, representing the amount of saline dissolved per kilogram of seawater) that enter the coastal waters of Jeju, it poses a threat to fish, shellfish, and other marine life around the island.

In addition to supplementing its existing monitoring system with a dedicated response system in conjunction with MOF and other agencies, the island also plans to take action to minimize damage ahead of time by reinforcing its step-by-step action guidelines according to water temperature and salinity (Levels 1 and 4) and lifting “closed season” status or relocating marine organisms to safe environments in the case of an emergency. With marine garbage posing another threat in addition to low-salinity water, the island plans to mobilize clean-up and fishing port management vessels for prompt collection efforts in cases where the garbage approaches within two miles of the coast.

In August 2016, joint fisheries suffered damage amid over 10 days of low-salinity water inflows chiefly affecting the western coast of Jeju. In 1996, the mass deaths of turban shells, abalone, and other fish and shellfish as a result of low-salinity water caused losses of over 5.9 billion won (US$4.9 million).

By Huh Ho-joon, Jeju correspondent

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