Find out more about the people behind Cawthron Institute.

Simon Stewart

Freshwater Scientist

Role at Cawthron

Simon is an ecosystem ecologist who researches nutrient cycling and food web processes. A common theme running through his research is identifying sources and pathways of nitrogen pollution and quantifying food web impacts. Simon has applied this research across the aquatic spectrum from headwater streams through to lakes and estuaries. Examples of this research include identifying and examining how nitrogen derived from invasive gorse affects streams and the macroinvertebrate communities; and, how nutrient recycling by food webs (i.e. nutrient excretion) mediates the response of lakes to increased catchment runoff.
While Simon’s research is applied in nature, he draws strongly on theoretical understanding of ecosystem and community ecology. This has been applied to a variety of applications ranging from lake restoration plans and analysis of monitoring data through to expert evidence on regional water quality policy and investigating novel monitoring tools. Simon has also worked on several MBIE funded research projects and contracted reports for regional councils and NGOs.


Technical skills, experience and interests

  • Preparing technical advice and expert evidence related to nutrient limits and management.
  • 10 years’ experience applying stable isotope biogeochemistry to applied environmental questions.
  • Development of methods for quantifying NH4+ δ15N and NO3- δ15N & δ18O and has widely applied bulk δ13C & δ15N as well as compound-specific amino-acid δ15N analyses on a range of food web samples.
  • Molecular ecology techniques (e.g. eDNA) for both streamlined routine biodiversity monitoring, as well as novel insights into aquatic food web structure.
  • Broad modelling background having experience with a range of mechanistic models from simple Lotka-Volterra predator-prey models through to highly resolved hydrodynamic fluid models.
  • Experience using a range of statistical models to analyse data, including expertise in using Bayseian mixing models to estimate diet composition in food webs.

Publication links

+64 3 548 2319 ex. 354
Simon.stewart@cawthron.org.nz