, Volume 32, Issue 3, pp 475–486 | Cite as

Dissolved Organic Matter Biogeochemistry Along a Transect of the Okavango Delta, Botswana

  • Kaelin M. Cawley
  • Piotr Wolski
  • Natalie Mladenov
  • Rudolf JafféEmail author


Biogeochemical processing of dissolved organic matter (DOM) in aquatic environments can alter its chemical quality and its bioavailability to the microbial loop. In this study, we evaluated the relative importance to DOM character of allochthonous and autochthonous DOM inputs and photo-degradation in a large, pristine wetland, the Okavango Delta of Botswana. We performed an intensive spatial sampling of surface water and analyzed for chemical and physical parameters (pH, conductivity, dissolved oxygen saturation, temperature, and channel depth), dissolved organic matter (DOM), and particulate organic matter (POM). We used UV–vis absorbance, fluorescence spectroscopy, and parallel factor analysis of excitation emission matrix data (EEM-PARAFAC) to characterize DOM. Our findings from principal component analysis (PCA) show downstream changes in DOM chemistry to be dominated by photo-degradation, suggesting that DOM in the Okavango Delta is transformed photo-chemically in shallower downstream reaches after being mobilized from the permanent swamp and seasonal floodplains. Additionally, we found that the PARAFAC model developed for the Everglades, a large, anthropogenically-altered wetland in North America, was well suited to tracking DOM dynamics in the Okavango Delta and may be useful for characterizing DOM in other sub-tropical, seasonally flooded wetlands.


DOM Fluorescence PARAFAC Photo degradation 



This study was funded in part by the George Barley professorship to R. Jaffé, by NSF through the FCE-LTER program (NSF DBI-0620409) and through the NPS-DOI Everglades Fellowship Program, and by grant NSF DEB-0717451 to N. Mladenov. The authors are indebted to M. Murray-Hudson from ORI for his insightful comments, to I. Mosie for field assistance, the SERC Water Quality laboratory for DOC analyses, and to the Okavango Research Institute for field and lab support. Our field team thanks the Shakawe Fishing Lodge for their generous donation of lodging. We thank Laurel Larsen and an anonymous reviewer for helpful comments on the manuscript. This is contribution number 541 from the Southeast Environmental Research Center.


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Copyright information

© Society of Wetland Scientists 2012

Authors and Affiliations

  • Kaelin M. Cawley
    • 1
  • Piotr Wolski
    • 2
  • Natalie Mladenov
    • 3
  • Rudolf Jaffé
    • 1
    • 4
    Email author
  1. 1.Southeast Environmental Research Center and Department of Chemistry and BiochemistryFlorida International UniversityMiamiUSA
  2. 2.Okavango Research InstituteUniversity of BotswanaMaunBotswana
  3. 3.Department of Civil EngineeringKansas State UniversityManhattanUSA
  4. 4.North MiamiUSA

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