Interactions between Phosphorus Enrichment and Nitrification Accelerate Relative Nitrogen Deficiency during Cyanobacterial Blooms in a Large Shallow Eutrophic Lake

Abstract

Regime shifts between nitrogen (N) and phosphorus (P) limitation, which trigger cyanobacterial succession, occur in shallow eutrophic lakes seasonally. However, the underlying mechanism is not yet fully illustrated. We provide a novel insight to address this from interactions between sediment P and nitrification through monthly field investigations including 204 samples and microcosm experiments in Lake Chaohu. Total N to P mass ratios (TN/TP) varied significantly across seasons especially during algal bloom in summer, with the average value being 26.1 in June and descending to 7.8 in September gradually, triggering dominant cyanobacterial succession from Microcystis to Dolichospermum. The regulation effect of sediment N/P on water column TN/TP was stronger in summer than in other seasons. Iron-bound P and alkaline phosphatase activity in sediment, rather than ammonium, contributed to the higher part of nitrification. Furthermore, our microcosm experiments confirmed that soluble active P and enzymatic hydrolysis of organic P, accumulating during algal bloom, fueled nitrifiers and nitrification in sediments. These processes promoted lake N removal and led to relative N deficiency in turn. Our results highlight that N and P cycles do not exist independently but rather interact with each other during lake eutrophication, supporting the dual N and P reduction program to mitigate eutrophication in shallow eutrophic lakes.

CyanoStrainChip: A Novel DNA Microarray Tool for High-Throughput Detection of Environmental Cyanobacteria at the Strain Level

“…Conversely, none of the other genera displayed a pattern comparable to that of Microcystis. Comparison of these findings with those of other studies confirms that Microcystis is the predominant bloom-forming genus in Lake Chaohu. , …”

“…Comparison of these findings with those of other studies confirms that Microcystis is the predominant bloom-forming genus in Lake Chaohu. 57 , 58 …”

“…Comparison of these findings with those of other studies confirms that Microcystis is the predominant bloomforming genus in Lake Chaohu. 57,58 Another remarkable observation in the CyanoStrainChip results was the variability of abundance change among strains within the same genus between different severity levels of blooms. Despite the overall trend of Microcystis being an increase, certain strains displayed a steady tendency.…”