Overview

Tropical freshwater lakes are critical natural systems of global importance, providing vital ecosystem services to some of Earth’s fastest growing and most vulnerable human populations, yet are scientifically under researched. Surprisingly little work has been carried out on productive tropical lakes, which are undergoing rapid catchment and environmental change under recent human activity (Ryves et al. 2011, Mills et al. 2017), with largely unknown impacts on key aspects of ecosystem function. Tropical lakes are excellent natural laboratories in which to study ecological responses to such environmental stressors, both at a community level (e.g. functional and taxonomic biodiversity) and for individual groups or species. In particular, tropical lakes provide exciting opportunities to explore evolutionary processes for keystone aquatic organisms. Daphnia spp. (water fleas) are ideal for such studies as they have both fast generational turnover, and produce eggs in protective cases, which can be hatched from seedbanks in lake sediments  

This PhD will address these questions 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, 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). Understanding how keystone aquatic species (e.g. Daphnia) adapt and evolve under environmental stress is crucial to evaluating the future resilience of these systems at a time when anthropogenic impacts increasingly drive global environmental change.

This PhD project combines contemporary limnology, ecology, and palaeolimnology (and specifically experimental ecology, genomics and “resurrection ecology”) across a suite of contrasting crater lakes in western Uganda. The aim is to characterise aquatic ecological response to environmental change over the last c.100-150 years. Specific objectives include addressing the extent to which catchment land use change over this period has affected aquatic biodiversity (focussing on primary producers and grazers from a genomic to community level) and productivity, and quantifying lake sedimentation and nutrient dynamics (e.g. C, Si). New sediment records collected within the project will critically test the linkages between environmental and ecological change. Outcomes of this project will shed new light on evolutionary responses to environmental perturbations with wide applicability (Orsini et al. 2013).

 

Top: Crater lake Wandakara, Uganda and (bottom) adult Daphnia (waterflea; left) and (right) dormant embryos decapsulated from the ephippium (red arrow), a protective chitin case.

Methodology

Crater lakes, in western Uganda, in different landscape settings and experiencing different recent histories in both forested and deforested catchments will be targeted. Lakes will be sampled for zooplankton and algal communities and a number of short sediment cores collected for analysis.

Using ‘resurrection ecology’ the student will hatch dormant specimens of Daphnia from lakes where environmental changes (eutrophication, climate) are known or can be inferred. Historical and modern populations will be used in experiments to document fitness changes that occurred in response to past environmental shifts, and analysed using cutting-edge multiomics approaches at the University of Birmingham (e.g. genome, transcriptome and metabolome analysis). Shifts in Daphnia ‘omics can be related to wider biophysical disruption, such as changes in algal community dynamics, through diatom analysis, and other proxies for aquatic and catchment change (such as nutrient cycling and C burial).

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 Makerere University Biological Field Station (MUBFS; http://caes.mak.ac.ug/mubfs/), likely spending up to 4 weeks in the field in western Uganda over the course of the PhD. Training in diatom analysis and other proxies will be given at Loughborough (LU) and BGS, and in Daphnia experimental ecology and genomic analyses at Birmingham (Dr Luisa Orsini), where the student is expected to spend a substantial part (c.1 year) of the PhD working on Daphnia.

Timeline

For further information about this project, please contact Dr David Ryves (D.B.Ryves@lboro.ac.uk) or Dr Luisa Orsini (l.orsini@bham.ac.uk). For enquiries about the application process, please contact the School of Social, Political and Geographical Sciences Research (spgsresearch@lboro.ac.uk). Please quote CENTA when completing the application form: http://www.lboro.ac.uk/study/apply/research/.

 

Partners and collaboration (including CASE)

The project will be in collaboration with Dr Luisa Orsini, School of Biosciences, University of Birmingham. Through Dr Keely Mills, there is also scope for collaboration with other BGS staff.

Further Details

For further information about this project, please contact Dr David Ryves (D.B.Ryves@lboro.ac.uk) or Dr Luisa Orsini (l.orsini@bham.ac.uk). For enquiries about the application process, please contact the School of Social, Political and Geographical Sciences Research (spgsresearch@lboro.ac.uk). Please quote CENTA when completing the application form: http://www.lboro.ac.uk/study/apply/research/.