Nitrification in the Upper Mississippi River: Patterns, controls, and contribution to the NO3- budget

Eric A. Strauss, William B. Richardson, Lynn A. Bartsch, Jennifer C. Cavanaugh, Denise A. Bruesewitz, Heidi Imker, Julie A. Heinz, David M. Soballe

Research output: Contribution to journalArticle

Abstract

We measured nitrification rates in sediment samples collected from a variety of aquatic habitats in Navigation Pool 8 of the Upper Mississippi River (UMR) 7 times between May 2000 and October 2001. We also conducted nutrient-enrichment experiments and analyzed vertical profiles of sediment to determine factors regulating nitrification. Nitrification rates were relatively high compared to other ecosystems (ranging from 0-8.25 μg N cm-2 h-1) and exhibited significant temporal and spatial patterns. Nitrification rates were greatest during the summer and spring compared to autumn and winter (ANOVA, p < 0.05) and were greater in contiguous backwater and impounded habitats compared to main and side-channel habitats (p < 0.05). Regression analysis indicated that nitrification rates were weakly (r 2 = 0.18, p < 0.0001) related to temperature and exchangeable NH4+ of the sediment. However, nutrient-enrichment experiments showed that NH4+ availability did not limit nitrification in 3 sediment types with variable organic matter. Vertical profiles of sediment cores demonstrated that oxygen concentration and nitrification had similar patterns suggesting that nitrification may be limited by oxygen penetration into sediments. We conclude that temperature and sediment NH4+ can be useful for predicting broad-scale temporal and spatial nitrification patterns, respectively, but oxygen penetration into the sediments likely regulates nitrification rates in much of the UMR. Overall, we estimated that nitrification produces 6982 mt N/y of NO3 - or 7% of the total annual NO3- budget.

Original languageEnglish (US)
Pages (from-to)1-14
Number of pages14
JournalJournal of the North American Benthological Society
Volume23
Issue number1
DOIs
StatePublished - Mar 1 2004
Externally publishedYes

Keywords

  • Nitrate budget
  • Nitrification
  • Nitrogen cycle
  • Upper Mississippi River

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science

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