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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Val H. Smith</dc:contributor>
  <dc:contributor>Jennifer L. Graham</dc:contributor>
  <dc:contributor>Dedmer B. Van de Waal</dc:contributor>
  <dc:contributor>Lenore Tedesco</dc:contributor>
  <dc:contributor>Nicolas Clercin</dc:contributor>
  <dc:creator>Theodore D. Harris</dc:creator>
  <dc:date>2016</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Recent studies have shown that the total nitrogen to total phosphorus (TN:TP) ratio and nitrogen oxidation state may have substantial effects on secondary metabolite (e.g., microcystins) production in cyanobacteria. We investigated the relationship between the water column TN:TP ratio and the cyanobacterial secondary metabolites geosmin, 2-methylisoborneol (MIB), and microcystin using multiple years of data from 4 reservoirs located in the Midwestern United States. We also examined the relationship between water column concentrations of chemically oxidized (NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;) and reduced (NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;) nitrogen, the NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;:NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;ratio, cyanobacterial biovolume, and associated secondary metabolites. We found that the cyanobacterial secondary metabolites geosmin, MIB, and microcystin primarily occurred when the TN:TP ratio was &amp;lt;30:1 (by mass), likely due to higher cyanobacterial biovolumes at lower TN:TP ratios. We also found that relative cyanobacterial biovolume was inversely related to the NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;:NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;ratio. Both N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;- and non-N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;-fixing cyanobacteria seemed to produce secondary metabolites and had higher concentrations per unit biovolume when NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;:NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;ratios were relatively low. Our data thus are consistent with the hypothesis that lower TN:TP ratios favor cyanobacterial dominance and also suggest that relatively low NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;:NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;ratios provide conditions that may favor the production of cyanobacterial secondary metabolites. Our data further suggest that increases in the absolute concentrations of TP or NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;(or both), causing decreases in TN:TP and NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;:NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;ratios, respectively, may stimulate cyanobacteria having the metabolic ability to produce geosmin, MIB, or microcystins. Future studies should address how the NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;:NH&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;ratio affects phytoplankton community structure and occurrence and production of cyanobacterial secondary metabolites.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.5268/IW-6.2.938</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Taylor &amp; Francis</dc:publisher>
  <dc:title>Combined effects of nitrogen to phosphorus and nitrate toammonia ratios on cyanobacterial metabolite concentrations ineutrophic Midwestern USA reservoirs</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>