Salt shortage

2019-03-08 09:08:08

By Peter Hadfield in Tokyo THIS summer’s floods in China were so severe that Japanese coastal waters, some 2500 kilometres away, experienced a drop in salinity of around 20 per cent. Researchers at the Seikai National Fisheries Research Institute in Nagasaki found that salinity between the islands of Cheju and Goto in August was 26 grams of salt per litre of water, or 26 practical salinity units (PSU), compared with a local average of between 32 and 33 PSU. That’s the lowest level since Japan’s Fisheries Agency established a network to monitor salt levels 30 years ago. Samples were taken from the layer of warm water between 0.5 metres and 15 metres below the surface. Below this depth, there is an abrupt shift to colder, saltier water. Even the Sea of Japan, separated from the East China Sea by a narrow neck of water, recorded a drop in salinity to just 27 PSU between the Tsushima Strait, near the South Korean city of Pusan, and Oki island. The Fisheries Agency says the profile of the mass of low-salinity surface water shows that it came from China’s eastern seaboard. Millions of tonnes of flood water poured out of the Yangtse and other Chinese rivers in July due to heavy rain. “We’re worried about the effect such widespread low salinity will have on fishing grounds and migration routes,” says Kozo Kitani, head of the East China Sea Fisheries Oceanography Division at the Seikai Institute. Three years ago floods in China caused a smaller drop in salinity, which resulted in a boom in jellyfish populations in the East China Sea,