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Cyanobacterial nitrogen fixation and phosphorus scavenging during a HAB forming (2018 NALMS)
Citation:
Lu, J., I. Struew2ing, AND N. Xu. Cyanobacterial nitrogen fixation and phosphorus scavenging during a HAB forming (2018 NALMS). 2018 NALMS International Symposium, Cincinnati, OH, October 29 - November 02, 2018.
Impact/Purpose:
1) The efforts towards reduction of nutrient contamination of surface waters has greatly gained attention to mitigate increasing incidences of harmful cyanobacterial blooms (HABs), but little attention has been paid on the roles and importance of N2-fixation and phosphorus scavenging pathways within the cyanobacterial communities during HABs. 2) A nitrogen fixation event was revealed, and this event was 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 by analyzing RNA sequences. 3) 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. 4) OW, regional offices, scientists and water quality managers could be interested in the results.
Description:
The efforts towards reduction of nutrient contamination of surface waters has greatly gained attention to mitigate increasing incidences of harmful cyanobacterial blooms (HABs), but little attention has been paid on the roles and importance of N2-fixation and phosphorus scavenging pathways within the cyanobacterial communities during HABs. The changes of global gene-expressions were examined to investigate the associations of upregulated genes with the levels of nitrogen and phosphorus, and with shift of cyanobacterial dominance and production of cyanotoxin using metatranscriptomic analyses prior to and during a toxic algal bloom that occurred in Harsha lake, OH. Expressions of genes involved in N2-fixation (nifDKH) and P transport and regulation (P-scavenging) were significantly upregulated during the bloom compared to pre-bloom time points. The activities of N2-fixation occurred during early summer after a late spring phytoplankton bloom were associated with high TP, low TN, and high relative abundance of active cyanobacterial N2-fixers dominated by Nostoc and Anabaena, resulting most likely in a following spur of Microcystis dominated early summer bloom, a shift of dominance from Nostoc and Anabaena to Microcystis and an increase of cyanotoxin production. By contrast P-scavenging activities dominated also by Nostoc and Anabaena were associated with low P (high N/P ratios) and increase of toxin producing Microcystis. 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.
