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Nitrogen fixation contribution to nitrogen cycling during cyanobacterial blooms in Utah Lake
Citation:
Li, H., T. Miller, J. Lu, AND R. Goel. Nitrogen fixation contribution to nitrogen cycling during cyanobacterial blooms in Utah Lake. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 302:134784, (2022). https://doi.org/10.1016/j.chemosphere.2022.134784
Impact/Purpose:
The efforts towards reduction of nutrient contamination of surface waters has greatly gained attention to mitigate increasing incidences of harmful cyanobacterial blooms (HABs). Little attention has been paid on the roles and importance of nutrient metabolic pathways within the cyanobacterial communities during HABs. The community successions and their metabolic pathway were revealed and found to be associated with low levels of nitrogen and high level of phosphorus, and with shift of cyanbacterial dominance from nitrogen fixing to bloom-forming populations and production of cyanotoxin. This information can be used to aid in the understanding the impact that TN and TP have on cyanobacterial community successions and cyanotoxin production and aid in making management decisions related to harmful algal blooms. OW, regional offices, scientists and water quality managers could be interested in the results.
Description:
Nitrogen (N) cycling is an essential process in lake systems and N-fixation is an important component of it. Recent studies have also found that nitrate reduction through heterotrophic denitrification in lake systems did not prevent harmful cyanobacterial blooms, but instead, may have favored the dominance of N2-fixing cyanobacteria. The overall objective of this study was to estimate nitrogen fixation rates and the expressions of associated nitrogenase (nif gene) functional gene at several sites at different occasions in freshwater Utah Lake. For comparison purposes, one time sampling was also conducted in the brackish Farmington Bay of Great Salt Lake (GSL). The microbial ecology of the top 20-cm of surface water was investigated to assess the dominant cyanobacterial communities and N-related metabolisms. Our study revealed that Dolichospermum and Nodularia were potential N2-fixers for Utah Lake and brackish Farmington Bay, respectively. The in situ N2-fixation rates were 0–0.73 nmol N hr−1L−1 for Utah Lake and 0–0.85 nmol N hr−1L−1 for Farmington Bay, and these rates positively correlated with the abundance and expressions of the nif gene. In addition, nitrate reduction was measured in sediment (0.002–0.094 mg N VSS−1 hr−1). Significantly positive correlations were found among amoA, nirS and nirK abundance (R = 0.56–0.87, p < 0.05, Spearman) in both lakes. An exception was the lower nirK gene abundance detected at one site in Farmington Bay where high ammonium retentions were also detected. Based on a mass balance approach, we concluded that the amount of inorganic N loss through denitrification still exceeded the N input by N2-fixation, much like in most lakes, rivers, and marine ecosystems. This indicates that N cycling processes such as denitrification mediated by heterotrophic bacteria contributes to N-export from the lakes resulting in N limitations.
URLs/Downloads:
DOI: Nitrogen fixation contribution to nitrogen cycling during cyanobacterial blooms in Utah Lake
https://pubmed.ncbi.nlm.nih.gov/35504465/