Red tide threatens southern coast

Hundreds of thousands of fish were found dead due to the red tide along the southern coast of the country, drawing ecological concerns over the algal bloom, provincial officials said Monday.

More than 330,000 sea breams, rockfish and other species raised in an aqua farm in Geoje, South Gyeongsang Province have died to the red tide, they said. Over 1.2 million are being raised in the two-hectare fish farm in the coastal city.

The dead fish were reported four days after the National Fisheries Research and Development Institute issued a red tide warning in the coast around Geoje and Goheung-gun in South Jeolla Province. This was the first red tide warning issued across the country this year.

The red tide, which is a type of algal bloom, produces natural toxins and depletes dissolved oxygen, killing the fish. It commonly occurs in coastal areas.

A warning is raised when the red tide occurs with a radius of over 5 kilometers and the concentration of cochlodinium exceeding 1,000 cells per milliliter. The government issues a red tide advisory when readings over 300 cells per milliliter are detected with a radius of 2 to 5 kilometers.

Chochlodinium, the culprit of the red tide, is known to proliferate in the sea at temperatures over 25 degrees Celsius.

The rising water temperature contributed to the red tide growth, the NFRD said. According to the organization, the average water temperature of the Korean coast has risen by 1.29 degrees Celsius over the past four decades.

The warning was also raised in the coastal city of Yeosu, South Jeolla Province on Thursday last week.

About 5.5 million fish are being raised in a 197-hectare fish farm in Yeosu, which is equivalent to 170 billion won ($144 million) of property. Last year, over 43,000 fish in Yeosu died to red tide, causing 70 million won in losses, officials said.

“The level of the red tide is falling thanks to the cloudy weather, but it can go up again once the sun gets stronger,” the Yeosu City Government said.

Red tide concerns have been escalating as it has been seen expanding to the East Sea.

On Saturday, the NFRD issued a red tide advisory in the coastal areas of Gyeongju and Pohang in North Gyeongsang Province.

As part of efforts to eliminate the algal bloom, municipalities have been spraying red clay in coastal waters with hundreds of ships. The red clay is known to soak up the minerals and minute plankton, thereby sinking the red tide algae toward the bottom of the sea. They have also used the propellers of fishing boats to deconcentrate the red tide.

By Lee Hyun-jeong  (rene@heraldcorp.com)