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

• Published in: Wetlands (Wilmington, N.C.) Vol. 32; no. 3; pp. 475 - 486
• Main Authors: Cawley, Kaelin M., Wolski, Piotr, Mladenov, Natalie, Jaffé, Rudolf
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.06.2012; Springer Nature B.V
• Subjects: Anthropogenic factors; Aquatic environment; Bioavailability; Biogeochemistry; Biomedical and Life Sciences; Chemistry; Coastal Sciences; Creeks & streams; Dissolved organic matter; Dissolved oxygen; Downstream; Ecology; Emission analysis; Environmental Management; Factor analysis; Floodplains; Floods; Fluorescence spectroscopy; Freshwater & Marine Ecology; Hydrogeology; Landscape Ecology; Life Sciences; Microorganisms; Nitrogen; Optical properties; Oxygen content; Particulate organic matter; Photodegradation; Physical properties; Principal components analysis; Rivers; Surface water; Water quality; Wetlands; Everglades; Florida; United States > US; Botswana; Okavango Delta; Fluorescence; Photo degradation; DOM; PARAFAC
• DOI: 10.1007/s13157-012-0281-0
• ISSN: 0277-5212

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.