MSc (Cape Town)
- Marine ecology
- Coastal and Estuarine ecosystems
- Nutrient cycling
I am a marine ecologist with a focus on human impacts in coastal and estuarine ecosystems. My research group investigates drivers of change in marine ecosystems and combines field and laboratory studies to understand how multiple stressors affect food web structure and biogeochemical cycling in coastal ecosystems.
I am also a member of the Coastal People: Southern Skies collaboration that connects communities with world-leading, cross-discipline research to rebuild coastal ecosystems.
Coastal People: Southern Skies
- MARI 301 Marine Ecology (course co-ordinator)
- MARI 450 Special Topic: Applied Estuarine Ecology (course co-ordinator)
Investigating linkages between land-use changes (in particular intensification of farming practices), in South Island, New Zealand, and ecological and biogeochemical shifts in recipient estuaries.
We have constructed nitrogen loading models for the South Island to estimate nutrient flux to estuaries based on different land use practices in the catchment. Stable isotope ratios in an opportunistic seaweed species reflected these different nitrogen loading regimes, providing a good indicator of local nutrient sources. We also documented shifts in growth rates of select bivalves and fishes and recorded changes in organic matter sources that support secondary consumers in the estuaries with greater nitrogen loads. To groundtruth the field surveys and transplant experiments, we have conducted laboratory experiments to quantify nutrient uptake and tissue turnover rates in select organisms. This research was supported by a Ministry of Fisheries Biodiversity Research grant.
We currently investigate spatial and temporal variation in rates of benthic denitrification in estuaries subject to different nitrogen loading regimes. This research aims to quantify nitrogen removal rates in pristine as well as nutrient enriched estuaries in South Island, New Zealand, and to investigate physicochemical and biological factors that correlate with coupled and direct denitrification. This research is supported by PBRF money made available to C. Savage.
Our research team also conducts work on nutrient fluxes and oxygen dynamics in subtidal sediments impacted by high organic matter loading from mussel farm deposits. In particular, we have a project on the potential of a bioturbator (sea cucumber) for the remediation of mussel impacted sediment. This work forms a component of a larger integrated aquaculture project with NIWA.
In order to understand the influence of humans against a background of natural variability in marine ecosystems, we have employed palaeoecological techniques to reconstruct historical changes in pristine and impacted coastal systems. In Fiordland, we use biomarkers (e.g., stable isotopes, pigments, lignin, BIT index), in water column samples and sedimentary records to reconstruct long-term change in productivity and organic matter sources to the fjords.
Part of this research involves identifying suitable biomarkers as proxies of refractory terrestrial organic matter and marine organic matter. Research is also underway to understand mechanisms that affect these proxies (particularly phytoplankton pigments) as they settle out of the water column and are incorporated into the sedimentary record. This research has been supported by University of Otago Research Grants and PBRF funds.
Coral reef ecosystems
My research has recently expanded to the tropical Pacific, where I am interested in how multiple stressors affect coral reef ecosystems. In particular, I am interested in how alterations in physicochemical factors (temperature, salinity, light environment), individually and combined, affect carbon cycling and implications of this for climate change.
Completed postgraduate students
- Josie Crawshaw - Thesis Title (PhD): Sinks of agriculturally derived nitrogen in coastal lagoons
- Ben Robertson - Thesis Title (PhD): Development of a cost-effective trophic state assessment protocol for shallow, temperate, tidal lagoon estuaries
- Sam Thomas - Thesis Title (PhD): The effects of multiple stressors on ecosystem functioning across a changing turbidity gradient in South Island estuaries