Wangsong, Myeoku, and Dongbang Reservoirs at High Risk of Algal Bloom This Summer

It has been found that Wangsong Reservoir in Uiwang, Gyeonggi Province, as well as Myeoku Reservoir and Dongbang Reservoir in Hwaseong, are at high risk of algal bloom this summer.

The Gyeonggi-do Institute of Health and Environment announced on April 22 that it had analyzed water quality, plankton, and fish in Wangsong Reservoir in Uiwang and Myeoku and Dongbang Reservoirs in Hwaseong last year, and published the "2025 Survey Report on Aquatic Ecosystems of Major Reservoirs in Gyeonggi Province" containing these findings.

The survey showed that all three reservoirs are in a "mesotrophic to eutrophic" state, meaning they are rich in nutrients. This indicates an environment with high concentrations of nutrients such as nitrogen and phosphorus in the water, allowing algae to proliferate easily. Particularly in summer, the concentration of nutrients tends to increase, leading to a higher likelihood of algal blooms.

For phytoplankton (microscopic algae that proliferate using sunlight and nutrients, causing algal blooms), different patterns of change were observed in each reservoir.

In Wangsong Reservoir, there has been a gradual improvement from a previous structure dominated by cyanobacteria—which cause algal blooms—towards a more diverse distribution of organisms.

Aerial View of Wangsong Reservoir in Uiwang

In contrast, Myeoku Reservoir showed significant fluctuations in water quality and biological changes, such as a rapid increase of certain algae depending on the season. Dongbang Reservoir continued to have a high proportion of cyanobacteria, maintaining a structurally eutrophic state.

Zooplankton (microscopic organisms that feed on phytoplankton and help maintain ecosystem balance) also exhibited typical patterns of increase and decrease depending on the season, though differences were seen in community structure.

Wangsong Reservoir displayed a relatively stable structure, with various species being replaced seasonally. However, Myeoku and Dongbang Reservoirs showed a simple community structure dominated by certain small organisms. A community structure repeatedly dominated by specific species may indicate low ecosystem stability or vulnerability to environmental changes.

The Gyeonggi-do Institute of Health and Environment analyzed that these differences are related to reservoir size, hydrological characteristics, and climate effects. In particular, it explained that high water temperatures and changes in rainfall patterns during summer act as factors that promote algal proliferation and changes in biological communities.

This content was produced with the assistance of AI translation services.