Dissolved organic nitrogen and phosphorus derived from different cyanobacteria regulate distinctly different nitrate
Junkai Gao1, Guanglong Liu2, Zhengui Xiong3
1Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China; College of Resources & Environment, Huazhong Agricultural University, Wuhan 430070, PR China.
Water Research
|September 6, 2025
Summary
Different algae blooms alter nitrogen cycling. Microcystis blooms favor dissimilatory nitrate reduction to ammonium (DNRA), increasing nitrogen. Dolichospermum blooms enhance denitrification, increasing phosphorus.
Area of Science:
- Aquatic microbial ecology
- Biogeochemical cycling
- Algal bloom dynamics
Background:
- Nitrate reduction pathways critically influence ecosystem nitrogen fate.
- Algal blooms significantly alter dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) composition.
- Understanding DON and DOP impacts on nitrate reduction is vital for aquatic ecosystem management.
Purpose of the Study:
- To investigate how different algal DON and DOP affect nitrate reduction pathways.
- To elucidate the mechanisms by which Microcystis and Dolichospermum blooms influence nitrogen cycling.
- To analyze the interplay between algal species, nutrient dynamics, and microbial communities.
Main Methods:
- Small-scale enclosure experiments were conducted.
- Analysis of DON and DOP composition, nutrient levels, and microbial communities.
- Quantification of nitrate (NO3--N) reduction pathways, including DNRA and denitrification.
Main Results:
- Microcystis blooms produced readily degradable DON, favoring DNRA and increasing nitrogen levels.
- Dolichospermum blooms produced decomposable DOP, promoting denitrification and increasing phosphorus levels.
- Mixed blooms supported denitrification, phosphorus accumulation, and algal-bacterial mutualism.
Conclusions:
- DON and DOP composition significantly shapes microbial communities and carbon availability.
- These factors govern the dominant nitrate reduction pathways (DNRA vs. denitrification).
- Algal species-specific contributions to DON/DOP dynamics are crucial for ecosystem nitrogen and phosphorus budgets.
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