Characteristics of the phytoplankton community and its relationship with water quality in Trieu Khuc lake, Hanoi

Abstract

Trieu Khuc lake is an important residential water body located in a traditional craft village area in Thanh Liet, Hanoi, currently under significant pressure from untreated domestic and production wastewater. This study aimed to assess the phytoplankton community structure and water quality using biological indices and physicochemical parameters. Sampling was conducted over nine surveys from May 2022 to January 2023 at four sites. A total of 74 species and subspecies belonging to six divisions were identified, with Chlorophyta dominating in species composition (50 %). However, Cyanobacteria dominated in cell density and determined the overall biomass of the lake. Phytoplankton density showed strong temporal variation, peaking in October 2022 (average 2.671 × 10⁶ cells/mL). Environmental parameters indicated severe degradation, with dissolved oxygen consistently below 1 mg/L, high turbidity, and signs of acidification. Biological indices, including Shannon - Wiener (H’ < 1), Palmer (14 - 16), and Bio-index, consistently indicated organic pollution and eutrophic conditions. The strong agreement between biological and physicochemical assessments suggests that the lake is heavily polluted and strongly affected by nutrient-rich wastewater inputs.