Article,
Consistent stoichiometric long-term relationships between nutrients and chlorophyll-a across shallow lakes
Affiliations
- [1] Helmholtz Centre for Environmental Research - UFZ [NORA names: Germany; Europe, EU; OECD];
- [2] Estonian University of Life Sciences [NORA names: Estonia; Europe, EU; OECD];
- [3] Middle East Technical University [NORA names: Turkey; Asia, Middle East; OECD];
- [4] Yunnan University [NORA names: China; Asia, East];
- [5] Sino-Danish Centre for Education and Research [NORA names: China; Asia, East];
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Abstract
Aquatic ecosystems are threatened by eutrophication from nutrient pollution. In lakes, eutrophication causes a plethora of deleterious effects, such as harmful algal blooms, fish kills and increased methane emissions. However, lake-specific responses to nutrient changes are highly variable, complicating eutrophication management. These lake-specific responses could result from short-term stochastic drivers overshadowing lake-independent, long-term relationships between phytoplankton and nutrients. Here, we show that strong stoichiometric long-term relationships exist between nutrients and chlorophyll a (Chla) for 5-year simple moving averages (SMA, median R² = 0.87) along a gradient of total nitrogen to total phosphorus (TN:TP) ratios. These stoichiometric relationships are consistent across 159 shallow lakes (defined as average depth < 6 m) from a cross-continental, open-access database. We calculate 5-year SMA residuals to assess short-term variability and find substantial short-term Chla variation which is weakly related to nutrient concentrations (median R² = 0.12). With shallow lakes representing 89% of the world’s lakes, the identified stoichiometric long-term relationships can globally improve quantitative nutrient management in both lakes and their catchments through a nutrient-ratio-based strategy.