, Volume 132, Issue 1–2, pp 1–22 | Cite as

Influence of catchment land use and seasonality on dissolved organic matter composition and ecosystem metabolism in headwater streams of a Kenyan river

  • Frank O. Masese
  • Jessica S. Salcedo-Borda
  • Gretchen M. Gettel
  • Kenneth Irvine
  • Michael E. McClain


Headwater streams influence the biogeochemical characteristics of large rivers and play important roles in regional and global carbon budgets. The combined effects of seasonality and land use change on the biogeochemistry of headwater streams, however, are not well understood. In this study we assessed the influence of catchment land use and seasonality on the composition of dissolved organic matter (DOM) and ecosystem metabolism in headwater streams of a Kenyan river. Fifty sites in 34 streams draining a gradient of catchment land use from 100% natural forest to 100% agriculture were sampled to determine temporal and spatial variation in DOM composition. Gross primary production (GPP) and ecosystem respiration (ER) were determined in 10 streams draining primarily forest or agricultural catchments. Absorbance and fluorescence spectrophotometry of DOM reflected notable shifts in composition along the land use gradient and with season. During the dry season, forest streams contained higher molecular weight and terrestrially derived DOM, whereas agricultural streams were dominated by autochthonous production and low molecular weight DOM. During the rainy season, aromaticity and high molecular weight DOM increased in agricultural streams, coinciding with seasonal erosion of soils and inputs of organic matter from farmlands. Most of the streams were heterotrophic. However, GPP and ER were generally greater in agricultural streams, driven by higher dissolved nutrient (mainly TDN) concentrations, light availability (open canopy) and temperature compared with forest streams. There were correlations between freshly and autochthonously produced DOM, GPP and ER during both the dry and wet seasons. This is one of the few studies to link land-use with organic carbon dynamics and DOM composition. Measures of ecosystem metabolism in these streams help to affirm the role of tropical streams and rivers as important components of the global carbon cycle and demonstrate that even semi-intensive, smallholder agriculture can have measurable effects on riverine ecosystem functioning.


Carbon cycling DOM composition Land use change Whole-stream metabolism Tropical streams 



We are grateful to Lubanga Lunaligo and David Namwaya (University of Eldoret) who assisted during lab work and Phillip Sigilai, Robertson Marindany and Kimutai Kitur for assistance during field work. We appreciate the technical assistance offered by Fred Kruis, Ferdi Battes, Lyzette Robbemont, Frank Weigman and Berrend Lolkema during sample analyses at the UNESCO-IHE laboratory in Delft, The Netherlands. Comments from Jacques C. Finlay and four reviewers helped to improve this manuscript. This is a publication of the MaraFlows Project and was funded by the Dutch Ministry of Foreign Affairs through the UNESCO-IHE Partnership Research Fund (UPaRF).

Supplementary material

10533_2016_269_MOESM1_ESM.xlsx (16 kb)
Supplementary material 1 (XLSX 16 kb)
10533_2016_269_MOESM2_ESM.xlsb (11 kb)
Supplementary material 2 (XLSB 11 kb)


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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Department of Fisheries and Aquatic SciencesUniversity of EldoretEldoretKenya
  2. 2.Department of Water Science and EngineeringUNESCO-IHE Institute for Water EducationDelftThe Netherlands

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