- Tropical lakes are important centres of biodiversity and hotspots of nutrient cycling but remain understudied
- Crater lakes in Western Uganda cover a range of lake types, size and recent catchment history
- This project combines field limnology and palaeolimnology to address this critical data gap in a key ecoregion
Tropical freshwater lakes are critical natural systems of global importance, yet are scientifically under researched. Their catchments provide vital ecosystem services to some of Earth’s fastest growing and most vulnerable human populations, but the provision of fundamental ecological and life-supporting services is under threat due to the impact of human activities acting at the landscape-scale in the current Anthropocene (Butzer, 2015). Separating anthropogenic impacts from natural variability on aquatic systems is a key challenge to understanding their past and present development in the Anthropocene, and so for managing livelihoods in East Africa into the future (e.g. NERC HyCRISTAL project).
Human activity often drastically alters both nutrient cycling and biodiversity in lakes and their catchments (Mills et al. in press). Lakes are now seen as hotspots of biogeochemical dynamics (e.g. for carbon, silicon, phosphorus) within their landscapes, especially in small lakes, which have the highest rates of nutrient cycling. Very little work has been carried out on productive tropical lakes, which are often undergoing rapid catchment and environmental change, with largely unknown impacts on these
This PhD will address this gap, in the lake-rich region of equatorial western Uganda, where there are ~100 crater lakes in 4 lake districts varying from shallow and saline, to deep and fresh (Mills & Ryves 2012), together comprising one of the world’s top 200 most biologically valuable ecoregions (Fig. 1) and acting as a natural aquatic laboratory. These freshwater lakes are important resources for drinking, irrigation and nutrition (e.g. fishing), as well as centres of aquatic and terrestrial biodiversity, within landscapes often heavily impacted by human activity (Fig. 1). Anticipating how ecosystems change in space and time is crucial to understanding the future resilience of these systems at a time when anthropogenic impacts increasingly drive global environmental change.
This PhD project combines contemporary and palaeolimnology across a suite of contrasting crater lakes in western Uganda with the aim of characterising environmental and ecological change over the recent past (Ryves et al. 2011; Mills et al. 2014), to link changes in lake functioning as hotspots of both biodiversity and biogeochemistry (e.g. C and Si burial) in the last ~100-150 years. Specific objectives include addressing the extent to which catchment land use change over this period has affected aquatic (especially algal) biodiversity and productivity, lake sedimentation and nutrient dynamics (e.g. C, Si), and critically testing the linkages between these using new sediment records collected within the project. Outcomes of this project will have great relevance for management of these crucial freshwater resources.
Crater lakes from western Uganda in different landscape settings and experiencing different recent histories in both forested and deforested catchments, i.e. both within and outside Kibale Forest National Park, will be targeted. Water chemistry profiling will be carried out at selected lakes over two field seasons and a number of short sediment cores collected for analysis (including 210Pb dating) from these lakes.
Sediment samples will be analysed for a range of biogenic and physical proxies (e.g. diatoms, biogenic silica, charcoal, organic C flux) to characterise recent changes in lake ecology and environment. This will be combined with analyses of contemporary water chemistry. There is scope to apply additional proxies to explore contemporary processes and recent change, such as analysis of pollen, GDGTs, fingerprinting anthropogenic pollutants, or stable isotopes indicative of nutrient cycling within the lake and catchment (e.g. 13C, 30Si) (BGS).
Training and Skills
CENTA students will attend 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes.
The PhD student will be fully supported during fieldtrips to Uganda by the supervisory team and MUBFS, spending up to two periods of 4-6 weeks in the field in western Uganda over the course of the PhD. The student will primarily stay at the Makerere University Biological Field Station (MUBFS) near Fort Portal within Kibale Forest National Park (http://chapmanresearch.mcgill.ca/Kibale/Facilities.html).
Training in diatom analysis, (palaeo)limnological and palaeoecological analysis and chosen proxies will be provided by LU or BGS. There will also be full training in appropriate health and safety issues, including first aid and boat handling.
Year 1 (2017-18): With PhD supervisors, establish research strategy and plan for fieldwork in Uganda. Arrange research permits from Ugandan Government, Uganda Wildlife Authority, and MUBFS and undergo all health and safety training. First main fieldwork period to coincide with dry season (during June – August 2018) accompanied by supervisory team.
Year 2 (2018-19): Plan and undertake second main fieldwork period with supervisors in Jan – Feb 2019 or June – July 2019 (dry seasons). Analyses continue in UK of samples collected from Uganda.
Year 3 (2019-20): Analysis of samples finishes and thesis writing. Major conference targeted for presentation of key findings in Year 3.
Partners and collaboration (including CASE)
The project will be in collaboration with Makerere University, Kampala, Uganda, and the PhD student will be staying at MUBFS (co-managed by Profs Colin and Lauren Chapman, McGill). Through Dr Mills, there is scope for collaboration with other BGS staff, for example Dr Chris Vane (organic geochemistry) and Prof Melanie Leng (stable isotopes), and elsewhere.
For further information about this project, please contact Dr David Ryves (D.B.Ryves@lboro.ac.uk).
For enquiries about the application process, please contact Susan Clarke, Department of Geography, Loughborough University (S.N.Clarke@lboro.ac.uk).
Please quote CENTA when completing the application form: http://www.lboro.ac.uk/study/apply/research/.