Kinetic aspects of humic substances derived from macrophyte detritus decomposition under different nutrient conditions
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Autochthonous particulate organic carbon (POC) is an important precursor of humic substances (HS), and macrophytes represent the major source of POC in tropical aquatic ecosystems. Autochthonous HS influence the carbon supply, light regime, and primary production within freshwater systems. This study addresses the conversion of POC from two macrophyte species into HS and their mineralization under different nutrient conditions (oligotrophic to hypereutrophic). A first-order kinetic model was adopted to describe the conversion routes. The POC conversion rate to HS for detritus derived from Paspalum repens was similar under different nutrient conditions, but eutrophication decreased the kR (global coefficient reaction) for detritus from Pistia stratiotes due to its high detritus quality (C:N:P ratio). Fulvic acids were the main fraction of HS in both plants. The mineralization of humic acids from P. stratiotes was inhibited at higher nutrient availability, while eutrophication increased the mineralization of fulvic acids from P. repens. The main route of POC cycling is humification through fulvic acid formation (up to 40% of POC). The intrinsic characteristics of the source detritus were the main forcing functions that stimulated the cycling of HS. In tropical aquatic ecosystems, the degradation of autochthonous carbon decreased due to eutrophication, thus contributing to the diagenetic process in the long term.
KeywordsDOC Fulvic acids Humic acids Carbon cycle Mineralization Kinetic model Eutrophication Tropical aquatic ecosystems
The authors would like to thank the critical contribution of Kevin Murphy (University of Glasgow, UK), who revised the English language in this manuscript.
The authors would like to thank the Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP (Process number 2012/21829-0) for their financial support.
- AES Tietê 2013. Available at http://www.aestiete.com.br/usinas/Paginas/BarraBonita.aspx. Accessed January 2016
- Azevedo JCR, Nozaki J (2008) Análise de fluorescência de substâncias húmicas extraídas da água, solo e sedimento da lagoa dos Patos-MS. Quim Nova 31:1324–1329Google Scholar
- Berg B, McClaugherty C (2008) Plant litter decomposition, humus formation,carbon sequestration, 2nd edn. Springer-Verlag, BerlinGoogle Scholar
- Hayes MHB, Swift RS (1978) The chemistry of soil organic colloids. In: Greenland DJE, M.H.B. H (eds) The chemistry of soil constituents. John Wiley & Sons, pp 179–318Google Scholar
- Steinberg CEW, Paul A, Pflugmacher S et al (2003) Pure humic substances have the potential to act as xenobiotic chemicals – a review. Fresenius Environ Bull 12:391–401Google Scholar
- Toming K, Tuvikene L, Vilbaste S, Agasild H (2013) Contributions of autochthonous and allochthonous sources to dissolved organic matter in a large, shallow, eutrophic lake with a highly calcareous catchment. Limnol Oceanogr 58:1259–1270. https://doi.org/10.4319/lo.2013.58.4.1259 CrossRefGoogle Scholar
- Torremorell A, Pérez G, Lagomarsino L, Huber P, Queimaliños C, Bustingorry J, Fermani P, Llames ME, Unrein F (2014) Microbial pelagic metabolism and CDOM characterization in a phytoplankton-dominated versus a macrophyte-dominated shallow lake. Hydrobiologia 752:203–221. https://doi.org/10.1007/s10750-014-2057-4 CrossRefGoogle Scholar
- Vollenweider RA (1968) Scientific fundamentals of the eutrophication of lakes and flowing water, with particular reference to phosphorus and nitrogen as factors in eutrophication. Tech Rep OECD Paris 159Google Scholar
- Westlake DF (1965) Some basic investigation of productivity of aquatic macrophytes. Mem Ist Ital Hidrobiol 18:229–248Google Scholar