Environment ministry develops domestic carbon formula to sharpen algae bloom forecasts

The environment ministry said Wednesday its research arm had developed South Korea's first carbon estimation equations tailored to 36 freshwater phytoplankton species, reducing the error in measuring algal carbon biomass by 26 to 39 percent compared with formulas developed abroad.

The National Institute of Environmental Research said the new equations reflect the biological traits of algae found in domestic rivers and reservoirs. Field and academic studies have until now relied on equations built from marine organisms, whose ecology differs from Korean freshwater systems, introducing substantial error when researchers tried to quantify the carbon in the phytoplankton that make up harmful blue-green algal blooms.

The equations were produced through a 2025 project tracing the origin a large algal bloom in the Nakdong River and forecasting how climate change will affect its size. Phytoplankton cells are too small to weigh individually, so the researchers combined digital microscope image analysis with an elemental analyzer to relate each cell's biovolume, the three-dimensional volume calculated from its measured length and width, to its carbon content.

That work yielded separate equations for different taxonomic groups, allowing carbon to be estimated from biovolume alone. Against the marine-derived formulas previously in use, the error fell 35 percent for cyanobacteria, 39 percent for diatoms and 26 percent for other algae.

Kim Kyung-hyun, head of the institute's water environment research division, called the work a successful case of developing technology to quantify domestic freshwater blooms as carbon biomass. "We will go through field verification and add carbon data to existing bloom observations to develop a monitoring and forecasting system the public can trust," he said.

The institute is part of the Ministry of Climate, Energy and Environment.