Journal
HARMFUL ALGAE
Volume 73, Issue -, Pages 84-97Publisher
ELSEVIER
DOI: 10.1016/j.hal.2018.02.001
Keywords
Cyanobacteria; Eutrophication; Lake Erie; Nitrogen; Phosphorus; RT-qPCR
Categories
Funding
- Ohio Sea Grant [NA14OAR4170067]
- National Science Foundation [OCE-1736629]
- Ohio EPA's Surface Water Improvement Fund
- Ohio EPA's Environmental Education Fund
- Friends of Stone Lab
- Cooperative Institute for Great Lakes Research
- Office of Research at Ohio State University
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The toxin-producing, bloom-forming cyanobacterial genera Microcystis and Planktothrix require fixed nitrogen (N), such as nitrate, ammonium, or organic N (e.g., urea) for growth and production of microcystins (MC). Bioavailable N can enter lakes in pulses via tributary discharge and through in-lake recycling, which can maintain low N concentrations. Additionally, light intensity has been suggested to play a role in MC production. This study examined how three forms of N (nitrate, ammonium, and urea) interacted with N loading rate (one large pulse vs. many small pulses) and light intensity to stimulate Microcystis and Planktothrix growth and MC production using nutrient enrichment experiments. Enrichments of nitrate, ammonium, and urea resulted in greater cyanobacterial biovolumes and MC concentrations than phosphorus-only enrichments, and there was no difference between pulse (100 mu mol/L) and press treatments (8.3 mu mol/L every 4 h). Analysis of mcyD transcripts showed significant up-regulation within 4 h of ammonium and urea enrichment. High light intensities (300 mu mol photons/m(2)/s) with N enrichment resulted in greater cyanobacterial biovolumes and MC concentrations than lower light intensities (30 and 3 mu mol photons/m(2)/s). Overall, the results suggest Microcystis and Planktothrix can use many forms of N and that high light intensities enhance MC production during elevated N concentrations. Moreover, the results here further demonstrate the importance of considering N, as well as P, in management strategies aimed at mitigating cyanobacterial blooms. (C) 2018 Elsevier B.V. All rights reserved.
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