Long-term changes in cyanobacteria and aquatic plants unveiled through sediment analysis

A new study published in Engineering offers insights into the long-term succession of cyanobacteria and aquatic plant communities in urban lakes, highlighting the impacts of urbanization and nutrient inputs on freshwater ecosystems. The research, led by Hongwei Yu and colleagues from the Chinese Academy of Sciences, utilized environmental DNA (eDNA) sequencing and chronological analysis of sediments to reconstruct the historical changes in these communities over nearly two centuries.

Urban lakes, such as Donghu Lake in Wuhan, China, have experienced significant ecological shifts due to rapid urbanization and climate change. These changes have led to alterations in biodiversity and community dynamics, with implications for water quality and ecosystem health. The study focused on Donghu Lake, where sediment cores were collected and analyzed to understand the long-term trends in cyanobacterial and aquatic plant communities from 1849 to 2020.

The researchers used eDNA sequencing to identify the presence of various cyanobacteria and aquatic plant genera in the sediment layers. The results revealed that the abundance and diversity of these communities have changed significantly over time. For instance, the study identified 20 genera of cyanobacteria and eight genera of aquatic plants in the sediment cores. The dominant cyanobacterial genera included Microcystis and Synechococcus, while Potamogeton and Vallisneria were the dominant aquatic plant genera.

The analysis showed that the nutrient status of Donghu Lake has been relatively high since 2010, indicating a period of eutrophication. The total nitrogen (TN) and total phosphorus (TP) contents in the sediments significantly influenced the richness and coverage of cyanobacterial and aquatic plant communities. The study found that the TN content in Donghu Lake varied from 998 to 4665 mg/kg, while the TP content ranged from 350.33 to 971.25 mg/kg. The total organic carbon (TOC) content also increased, particularly after 2009, reaching up to 42.08 g/kg.

The study also examined the impact of land use changes and urbanization on the lake ecosystem. Remote sensing data revealed that the expansion of urban and industrial areas around Donghu Lake led to increased land surface temperatures and changes in land use patterns. These changes, combined with nutrient inputs from urban activities, have contributed to the observed ecological shifts in the lake.

The research identified key change points in the community structure of cyanobacteria and aquatic plants. For example, a significant change point in the cyanobacterial community was observed in 1972, marking a transition from a relatively stable state to one with increased cyanobacterial abundance. Similarly, the aquatic plant community experienced a significant change point in 1961, followed by a decline in species richness after 1999.

The findings suggest that urbanization and nutrient inputs have driven regime shifts in the Donghu Lake ecosystem, leading to transitions between clear-water states dominated by aquatic plants and turbid-water states dominated by cyanobacteria. The study emphasizes the importance of understanding these historical trends to develop effective management strategies for urban lakes.

The research provides valuable insights into the long-term succession of cyanobacteria and aquatic plants in urban lakes, highlighting the need for sustainable urban development and nutrient management to protect freshwater biodiversity. Future studies should focus on integrating diverse biological monitoring techniques to gain a more comprehensive understanding of these complex ecosystems.

The paper “Long-Term Succession in Cyanobacteria and Aquatic Plant Communities: Insights from Sediment Analysis,” is authored by Hongwei Yu, He Ji, Yang Li, Jing Qi, Baiwen Ma, Chengzhi Hu, Jiuhui Qu. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.04.012. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.