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Previous research updates

Read research updates from our investigators as their projects evolve.

Hilltop to Oceans: exploring the role of estuaries in processing nitrogen at the land-sea interface

Emily Douglas | Postdoctoral Research Fellow working on a Hilltops to oceans project for the George Mason Centre for the Natural Environment
Postdoctoral research fellow, Emily Douglas.

Emily Douglas, a postdoctoral research fellow working out of the University of Waikato in collaboration with the Institute of Marine Science, is embarking on one of the latest projects for the George Mason Centre for the Natural Environment.

Emily will be investigating how estuary habitats store and process nitrogen, under the guidance of Professor Conrad Pilditch (School of Science, University of Waikato) and Associate Professor Luitgard Schwendenmann (School of Environment, University of Auckland).

“The rationale for this project comes from an urgent need to advance the knowledge and awareness of estuary ecosystems and the important part they play in storing, processing and especially removing (by denitrification) excess land-derived nitrogen,” Emily explains.

“We will use an interdisciplinary approach to determine the linkages between stressors (excess nutrients, organic matter and muddy sediments), and impacts on biogeochemical processes (especially denitrification) in receiving estuary habitats."

She will be seeking answers to the following questions:

  1. Are there denitrification hotpots in estuaries, and are these associated with particular habitats?
  2. What environmental factors control denitrification in estuarine systems?

Emily will be conducting her research in the Mahurangi Harbour and other estuaries in northern New Zealand where measurements will be made in key habitats such as intertidal flats, seagrass beds, subtidal channels, and mangrove fringes.

This project follows on from Emily's PhD research which showed that maintaining biodiversity of soft sediment habitats as well as reducing the ‘muddying’ of estuaries will be important for ecosystem resilience to future nutrient enrichment stress.

Associated information


Meet our first GMCNE researchers

In February we hosted a small event to connect supporters of the George Mason Centre for the Natural Environment with the first researchers funded by the Centre.

Guests met the investigators whose projects were selected and heard details on the exciting work the Centre is undertaking.

A video clip of the presentations detailing this interdisciplinary research can be viewed on the left. 


Hilltop to Oceans: processes of change and mitigating impacts

Dr Luitgard Schwendenmann, School of Environment, sampling leaf litter and water in the Waitakere Ranges
Dr Luitgard Schwendenmann sampling leaf litter and water in the Waitakere Ranges

Primary investigators: Dr Luitgard Schwendenmann, School of Environment & Emily Douglas, Caitlin Blain, Jenny Hillman

Land use intensification, particularly agricultural, is significantly increasing sediment, nutrient, and organic matter loads to freshwater and coastal ecosystems.

Recent research suggests there may be a tipping point where muddiness exceeds a critical level, significantly affecting denitrification (the microbial conversion of bioavailable nitrogen into inert N2 gas) in estuaries.

Dr Luitgard Schwendenmann says sediment and nutrient input may lead to the loss of marine vegetation, such as seagrasses and kelp forests.

“This decreases the capacity of our coastal ecosystems to act as carbon reservoirs and significantly impacts kai moana, particularly shellfish beds,” she says.

“Our project will look at the cascading effects of land use change on carbon and nutrient cycling in freshwater and coastal ecosystems around the Hauraki Gulf, the role of natural ecosystems in mitigating negative effects and the potential for enhancement through restoration of our estuarine and coastal ecosystems.”

The goal is to provide practical new research and techniques that communities can use to increase the successful restoration of seagrasses, kelp forests and, ultimately, shellfish beds.

(January 2018)

Advanced sensor technology for tracking woody debris

Advanced sensor technology for tracking woody debris (GMCNE project)
Advanced sensor technology for tracking woody debris (GMCNE project)

Primary investigator: Dr Heide Friedrich, Deputy Head, Department of Civil and Environmental Engineering, Faculty of Engineering

Dr Heide Friedrich’s project is focussed on better understanding the interactions between sediment and large woody debris (LWD) trapped in our waterways.

“In New Zealand, the flow of many of our streams and rivers is influenced by the sediment and LWD [sometimes referred to as driftwood] from waste, bank erosion, forestry and other land use activities,” Dr Friedrich says.

“Wood jams lead to culverts and bridges being blocked and have a significant impact on property and road crossings.”

As part of the project PhD Engineering student Gabriel Spreitzer will be using new technology to track the way sediment and LWD moves through our waterways.

“Understanding the dynamics of how wood jams form and persist is important for design guidelines, managing the accumulation of sediment, as well as establishing what impacts it might have on habitats and infrastructure,” he says.

Much of the work will take place in the laboratory where natural scenarios can be simulated in a controlled environment. The team will model and scale the scenarios using either machined logs or real debris (small size) – and the observed processes can then be upsized to prototype scale.

“By controlling key variables such as water and sediment discharge, channel geometry, bridge alignment, and wood structure - and capturing the resulting data - we can gain some understanding of characteristic sequences of jam development and the statistical likelihoods of different types of jams,” explains Gabriel’s co-supervisor, Dr Jon Tunnicliffe from the School of Environment.

The knowledge gained through this research will allow the project team to better understand the risk natural hazards pose to New Zealand ecosystems. It will inform New Zealand’s freshwater and forestry management systems and help make New Zealand’s environmental infrastructure more resilient.

Dr Friedrich presented the preliminary research (on which this project is based) at the 2017 American Geophysical Union (AGU) Fall Meeting in New Orleans, in December.

AGU's Fall Meeting is the largest Earth and space science meeting in the world and serves as a platform for scientists to present and discuss cutting-edge research.

(December, 2017)