Analysis of sediment from a lake in China has revealed the impact of urbanisation and nutrient inputs on freshwater ecosystems over two centuries.

The study focused on Donghu Lake in Wuhan, China, where sediment cores were collected and analysed to understand long-term trends in cyanobacterial and aquatic plant communities from 1849 to 2020. Led by Hongwei Yu and colleagues from the Chinese Academy of Sciences, the results revealed that the abundance and diversity of these communities have changed significantly over time.

Many urban lakes have experienced significant ecological shifts due to rapid urbanisation and climate change. These changes have led to alterations in biodiversity and community dynamics, with implications for water quality and ecosystem health.

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 nitrogen and phosphorus present in the sediments significantly influenced the richness and coverage of cyanobacterial and aquatic plant communities.

The study also examined the impact of land use changes and urbanisation on the lake ecosystem. Remote sensing data revealed that the expansion of urban and industrial areas around Donghu Lake has 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. In 1972, a significant change point in the cyanobacterial community was observed, marking a transition from a relatively stable state to one with increased cyanobacterial abundance. Similarly, the aquatic plant community experienced significant change in 1961, followed by a decline in species richness after 1999.

The findings suggest that urbanisation 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 emphasises the importance of understanding these historical trends to develop effective management strategies for urban lakes.

The research, published in Engineering journal, 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.