The Seoul City government on Thursday issued its first algae advisory in four years after two consecutive tests on the Han River showed excessive concentration of the blue-green microorganisms.
The affected area is a tributary running from the Gangdong Bridge to the Jamsil Bridge, in the eastern part of the capital’s river. This is the sixth algal alert issued in the city since 2000.
The announcement confirmed that the algal blooms have now been spreading through the upper and lower parts of the river.
Late last month, an algae advisory was issued in the upper parts of the Han River in Gyeonggi Province.
“The city expects the algae levels will not further increase to the point of issuing a higher warning level,” a Seoul City official said.
In the second test conducted on Wednesday, the concentration levels of chlorophyll a at five water intake facilities in Guui-dong and Poonap-dong ranged from 14.3 milligrams per cubic meter to 34.2. The number of algal cells measured from 1180 to 4470 per liter of water.
An algal advisory is issued when the concentrations of chlorophyll a are 15 milligrams per cubic meter or above and 500 blue-green algal cells or more are detected in two consecutive tests.
A warning is issued when the chlorophyll a concentration exceeds 25 milligram per cubic meter and 5,000 algal cells are found.
Rapid increases in algae are typically caused by nutrient enrichment, high temperatures and still water conditions.
The algal blooms in the Nakdong River have also spurred people’s anxiety as civic environmental groups claimed that a toxin, called microcystis, which can cause liver damage, has been found.
The river is the drinking water source for people in the Gyeongsang provinces and the cities of Busan and Daegu.
Even though the Environment Ministry said recently that the increase in algae was caused by heat and drought, some activists blame the government’s four river project, which they say has slowed river flows.
The Environment Ministry and local governments say they will watch the situation closely and conduct more tests to ensure the safety of the water.
People expressed their worries and anxiety, posting pictures of the dark green surfaces of rivers on social networks. They describe the green water as “green algae latte.”
