To properly conserve, restore and manage riverine ecosystems and the services they provide, it is pertinent to understand their functional dynamics. Growing human populations and high dependency on natural resources in developing countries have exerted pressure on land and water resources. However, there is a major knowledge gap concerning the influence of human activities on the functioning of tropical rivers in terms of organic matter processing and energy sources supporting riverine consumers.
This thesis explores the functioning of tropical upland streams and savanna rivers by assessing the spatial and temporal dynamics in organic processing under different land-use and discharge conditions and the resultant influence on energy sources for riverine consumers.
This thesis contributes to the theories of river functioning and has improved understanding of the functioning of African tropical streams by identifying a diverse macroinvertebrate shredder guild and determining its role in organic matter processing. This thesis also shows that large mammalian herbivores enhance terrestrial-aquatic food web linkages in African savanna rivers via the transfer of organic matter. The findings of this researcht are useful for defining future research needs and actions for sustainable management of agriculturally influenced streams and savanna rivers in landscapes witnessing declining wildlife populations and changing land uses.
1. General introduction and study rationale
2. Anthropogenic influences on the structure and functioning of riverine ecosystems in the Lake Victoria basin
3. Macroinvertebrate functional feeding groups in Kenyan highland streams: implications for organic matter processing
4. Litter processing and shredder distribution as indicators of riparian and catchment influences on ecological health of tropical streams
5. Linkage between DOM composition and whole-stream metabolism in headwater streams influenced by different land use
6. Partitioning the relative importance of different sources of energy for consumers on the longitudinal gradient of the Mara River, Kenya
7. Synthesis and conclusions
IHE Delft PhD programme leads to a deepening of a field of specialisation. PhD fellows do scientific research, often with conclusions that directly influence their region. At IHE Delft, PhD researchers from around the world participate in problem-focused and solution-oriented research on development issues, resulting in an inspiring research environment. PhD fellows work together with other researchers from many countries dealing with topics related to water and the environment.
PhD research is often carried out in the ‘sandwich’ model. Preparation and final reporting – the first and last portion of the programme – are carried out in Delft, while actual research is done in the fellow’s home country, under co-supervision of a local institute. Regular contacts with the promotor are maintained through visits and long-distance communication. This enables researchers to employ solutions directly to problems in their geographical region.
IHE Delft PhD degrees are awarded jointly with a university. The degrees are highly valued and fully recognised in all parts of the world.