The researchers studied the water quality of Hassel Sea in 2021 to understand its eutrophication levels. They analyzed elements like total phosphorus, total nitrogen, transparency, and chlorophyll a in May and July. The lake was found to be more eutrophic in July than in May, with a trend of worsening eutrophication over time. Chlorophyll a, transparency, and total phosphorus were key factors contributing to eutrophication. Algal species were highly sensitive indicators of eutrophication, suggesting a high risk of water bloom in Hassel Sea.