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Laboratory-determined Phosphorus Flux from Lake Sediments as a Measure of Internal Phosphorus Loading
Published on: March 6, 2014
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How internal nutrient loading forms in shallow lakes: Insights from benthic organic matter mineralization
Xiaolong Yao1, Runnan Ding2, Yongqiang Zhou1
1State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
Water Research
|September 13, 2023
Summary
Internal nutrient loading from lake sediments fuels eutrophication, especially during algal blooms. Sediment organic matter and microbial processes significantly drive nutrient release, impacting shallow lake ecosystems.
Area of Science:
- Environmental Science
- Limnology
- Biogeochemistry
Background:
- Internal nutrient loading is a primary driver of shallow lake eutrophication, particularly after external load reductions.
- Understanding the interplay between sediment properties, microbial activity, and nutrient release is crucial for managing lake ecosystems.
- Previous research has quantified nutrient pools but lacked clarity on the specific links between substrates, microbial processes, and nutrient release dynamics.
Purpose of the Study:
- To investigate the relationships between sediment organic matter characteristics, microbial nitrogen (N) transformations, and nutrient fluxes across the sediment-water interface (SWI) in shallow lakes.
- To elucidate the causal links between sediment physicochemical parameters, N transformation rates, and nutrient release dynamics.
- To assess the contribution of sediment N mineralization to nutrient availability during algal blooms in Lake Taihu.
Main Methods:
- Characterization of sediment organic matter using optical measurements.
- Measurement of lake-wide sediment gross nitrogen transformations via the stable isotope (15N) dilution technique.
- Incubation of intact sediment cores to measure respiration and nutrient fluxes across the SWI using continuous-flow methods.
- Application of partial least square path models to analyze cause-effect relationships among variables.
Main Results:
- Environmental factors influencing N transformation rates varied seasonally, with sediment-derived dissolved organic matter being a key driver during summer algal blooms.
- Sediment organic matter mineralization showed significant positive effects on porewater nutrient concentrations and subsequent nutrient fluxes across the SWI.
- A strong positive correlation was observed between gross N mineralization rates and ammonium fluxes, indicating substantial inorganic N supply from sediment N mineralization during N-limited periods.
Conclusions:
- Sediment organic matter properties and microbial processes are fundamental drivers of internal nutrient loading in shallow lakes.
- Sediment N mineralization provides a significant source of inorganic nitrogen supporting algal blooms, especially during periods of lake nitrogen limitation.
- This study offers critical insights into the mechanisms of substrate- and microbial process-driven internal nutrient loading, essential for effective lake management and restoration.
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