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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>A. Giblin</dc:contributor>
  <dc:contributor>J. McClelland</dc:contributor>
  <dc:contributor>J. Tucker</dc:contributor>
  <dc:contributor>B. Peterson</dc:contributor>
  <dc:creator>C. Tobias</dc:creator>
  <dc:date>2003</dc:date>
  <dc:description>&lt;p&gt;Sediment&lt;span&gt;-water&amp;nbsp;&lt;/span&gt;fluxes&lt;span&gt;&amp;nbsp;of NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;, NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;, dissolved inorganic carbon, and O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;were measured&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;cores collected from the upper Rowley River&amp;nbsp;&lt;/span&gt;estuary&lt;span&gt;, Massachusetts, and used to calculate rates of organic&amp;nbsp;&lt;/span&gt;nitrogen&lt;span&gt;&amp;nbsp;(N) mineralization, nitrification, and coupled and direct denitrification (DNF). The cores contained&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N label&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;&lt;/span&gt;benthic&lt;span&gt;&amp;nbsp;microalgae (BMA) and&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the overlying water as&amp;nbsp;&lt;/span&gt;a&lt;span&gt;&amp;nbsp;result of an ongoing whole-&lt;/span&gt;estuary&lt;span&gt;&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NO&amp;nbsp;&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;enrichment study (NISOTREX II). The tracer allowed for estimation of gross NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;regeneration&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;sediments and the contribution of BMA derived N to total mineralization. The mean mineralization rate between sites was 16.0 ± 2.0 mmol N m&lt;/span&gt;&lt;sup&gt;-2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;d&lt;/span&gt;&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;. Approximately 13 to 56% of the mineralized N was nitrified at rates ranging from 1.8 to 10.1 mmol N m&lt;/span&gt;&lt;sup&gt;-2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;d&lt;/span&gt;&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;. Total denitrification was dominated by direct DNF (3.6 mmol N m&lt;/span&gt;&lt;sup&gt;-2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;d&amp;nbsp;&lt;/span&gt;&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;) furthest upstream, where NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;concentrations were highest. Coupled DNF was most important (8.0 mmol N m&amp;nbsp;&lt;/span&gt;&lt;sup&gt;-2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;d&lt;/span&gt;&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;)&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the sediments with high nitrification and low water column NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;.&amp;nbsp;&lt;/span&gt;A&lt;span&gt;&amp;nbsp;gross NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;flux&lt;span&gt;&amp;nbsp;from sediments to water of 0.9 to 2.1 mmol N m&lt;/span&gt;&lt;sup&gt;-2&lt;/sup&gt;&lt;span&gt;&amp;nbsp;d&lt;/span&gt;&lt;sup&gt;-1&lt;/sup&gt;&lt;span&gt;&amp;nbsp;was estimated from the isotope dilution of δ&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NO&amp;nbsp;&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the overlying water of the cores. The isotope dilution seen&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the cores was also detected as&amp;nbsp;&lt;/span&gt;a&lt;span&gt;&amp;nbsp;deviation from conservative δ&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;mixing along estuarine transects. Incorporation of this NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;&lt;span&gt;&amp;nbsp;regeneration into the DNF calculations effectively increased the estimate of direct DNF by up to 50% and decreased the coupled DNF estimate by up to 220%. Increasing δ&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the water of the cores indicated that the&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N-labelled BMA were preferentially mineralized over bulk&amp;nbsp;&lt;/span&gt;sediment&lt;span&gt;&amp;nbsp;organic N. Additional&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N enrichments&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the&amp;nbsp;&lt;/span&gt;sediment&lt;span&gt;&amp;nbsp;bacterial biomarker diaminopimelic acid showed&amp;nbsp;&lt;/span&gt;a&lt;span&gt;&amp;nbsp;link among&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N-labeled BMA, active bacteria, and&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NH&amp;nbsp;&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;released to the overlying water. Based on δ&amp;nbsp;&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;enrichments&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the cores, BMA accounted for approximately 50 to 100% of the N mineralized. An isotopic enrichment of δ&lt;/span&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;above background&amp;nbsp;&lt;/span&gt;in&lt;span&gt;&amp;nbsp;the&amp;nbsp;&lt;/span&gt;estuary&lt;span&gt;&amp;nbsp;was observed at&amp;nbsp;&lt;/span&gt;a&lt;span&gt;&amp;nbsp;magnitude consistent with the core-based rates of BMA mineralization. These results provide further evidence that BMA are not unidirectional sinks for water column-dissolved organic&amp;nbsp;&lt;/span&gt;nitrogen&lt;span&gt;, but instead act to turn over N between sediments and estuarine water on the scale of days.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.3354/meps257025</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Inter-Research Science Publisher</dc:publisher>
  <dc:title>Sediment DIN fluxes and preferential recycling of benthic microalgal nitrogen in a shallow macrotidal estuary</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>