Research

I am an ecologist interested in the impact of global change on trophic interactions and ecosystem functioning. I am currently a postdoctoral fellow based at Imperial College London, working with Prof. Guy Woodward. 

Previously I was at the University of Pretoria, funded by the Centre for Invasion Biology (Stellenbosch University; http://academic.sun.ac.za/cib/)
                              
My research broadly focuses on two areas of interest; the impact of global environmental change in freshwater ecosystems and the application of stable isotope analysis to answer ecological questions. Below I have outlined some current projects:

Global warming in freshwater ecosystems

Climate change is causing temperatures around the world to increase with negative implications for many

species. At an individual level warming can cause changes in growth rates and shifts in range. However, we need more information on how whole communities of interacting

species (i.e. food webs) are altered by temperature shifts. I am a postdoc on 'The Ring of Fire Project' which aims to quantify the gene-to-ecosystem impacts of warming with field sites across the Arctic. 



Multiple stressors in freshwater ecosystems

The acceleration of global change highlights the increasing need to quantify the nature of interactions among multiple stressors affecting biodiversity and ecological processes across a broad range of ecosystems. 
Freshwater ecosystems are particularly vulnerable to global change; a recent WWF report found average population declines of 76% among freshwater species since 1970 compared to 39% in terrestrial and marine species.  

I am working on a number of projects, including a meta-analysis, laboratory experiment and a field project (funded by the British Ecological Society) to explore the combined impacts of stressors in freshwaters.

Stable isotopes and food webs

Stable isotope analysis is a valuable tool to infer trophic links and characterise food web structure because the isotope signature of the body tissue of a consumer will reflect that of what it has eaten (essentially, ‘you are what you eat’). I am involve in a number of projects using isotopes including:
  • The diet of invasive fish in South Africa.
  • Food web structure in the Zambezi and Okavango Rivers, Namibia. 
  • Fish production across a temperature gradient in Iceland.
Invasive species and resource exchange

Predicting the impacts of biological invasions on native communities is increasingly important in our changing world. There is increasing evidence that invaders interrupt resource flows and disrupt natural ecological relationships instigating trophic cascades which can propagate across ecosystem boundaries.

Across numerous field sites in South Africa, I am quantifying the impact of riparian and freshwater invasions on resource exchange between the two linked ecosystems using stable isotope analysis. 

Lake Naivasha and catchment, Kenya

There are numerous invasive species in Lake Naivasha including water hyacinth, common carp, red swamp crayfish and large-mouthed bass. I have been working on Lake Naivasha and its primary tributary, the River Malewa, since 2008 using a combination of techniques including stable isotope analysis and in situ enclosure experiments to examine interactions among invaders and the implications for ecosystem structure and functioning.


Hengill geothermal region in Iceland

Insect emergence traps in the Drakensberg National Park, South Africa

Native mountain catfish, 
Amphilius natalensis, from the Drakensberg, SA

Lake Naivasha, Kenya

Louisiana red swamp crayfish, Procambarus clarkii, from the River Malewa, Kenya 


Fieldwork on the River Malewa, Kenya