Dr Kate O Brien

Senior Lecturer

+61 7 336 53534

School of Chemical Engineering
The University of Queensland
St Lucia, 4072



  • 2003 PhD The University of Western Australia  The effects of turbulent mixing on the vertical distribution of phytoplankton populations”  Supervisors Greg Ivey, David Hamilton, Anya Waite
  • 1994 Bachelor of Chemical Engineering, Honours I, The University of Queensland, Australia
  • 1994 Bachelor of Science (Mathematics) The University of Queensland, Australia



I undertake research in environmental systems modelling, analysis and synthesis.  This involves working in interdisciplinary teams with ecologists, engineers, remote sensing and field scientists to develop and apply models to address important environmental questions, and to use systems analysis and resilience thinking to identify key controlling variables.  A key question driving my research is, how can scientific knowledge in complex systems be synthesized to inform management actions and promote sustainability?  

Current projects include:

Identifying thresholds for seagrass loss, recovery and viability  

Seagrass meadows provide essential ecosystem services in the coastal zone and are in decline worldwide.  Identifying areas at risk of seagrass loss is crucial for effective monitoring and management because seagrass loss is difficult to reverse once it commences.  This project uses a multiple-model approach to identify thresholds for seagrass loss, recovery and viability.  Initial modelling and analysis is underway using historical data in Moreton Bay, Queensland, and this analysis will be extended to other regions.  

Collaborators: Bill Dennison, Chris Roelfsema, Megan Saunders, Javier Leon Patino, David Callaghan, Alistair Grinham, Angus Ferguson, Peter Mumby, Daniel Tuazon. Student research and PhD projects available. 

Seagrass as an ecological indicator: addressing challenges of complexity and scale  

Seagrasses play a vital role in coastal ecosystems.  Management agencies spend substantial resources in monitoring seagrass.   However the key goal of predicting seagrass status under future scenarios remains elusive, despite an increasing availability of data and detailed scientific studies.  This project addresses the three key barriers to predicting seagrass status: choice of indicator, reconciling scale and assigning causality in complex systems.  

Collaborators: Michelle Waycott, Len McKenzie, Gary Kendrick, Kath McMahon, Peter Scanes, Angus Ferguson, James Udy. Student research and PhD projects available. 

Nutrient and sediment retention in reservoirs:  costs and implications for land fertility, eutrophication and global phosphorus availability

The loss of soil, nitrogen and phosphorus from terrestrial systems to aquatic systems has increased substantially over the past half-century due to accelerated land-use change, vegetation clearing and fertilizer application.  However impoundment of waterways has reduced the load of sediment and nutrient delivered to the ocean from many river systems.  The result has been the accumulation of nutrient and sediment material in reservoirs.   This study aims to quantify the magnitude, uncertainty and dynamics of phosphorus, nitrogen and sediment retained by a number of Australian reservoirs, and assess the implications for economics, land fertility, eutrophication and global P availability.  

Collaborators: Michele Burford,Tony Weber, Cath Leigh, Adrian Volders, Jon Olley, Badin Gibbes, Alistair Grinham. Student research and PhD projects available. 

Planetary quotas: addressing the tragedy of the commons on a global scale

(Rockstrom et al. 2009) defined "planetary boundaries" for 9 earth systems processes, within which we can expect to maintain a "safe operating space" for humanity.  A number of these thresholds have already been exceeded, and we are accelerating towards others.  The fundamental challenge humanity faces can be characterized as the “tragedy of the commons”: whereby we benefit individually and immediately from actions which lead to long-term consequences shared across a wider population.  For example, the greenhouse gas emissions generated from a flight to Sydney for the weekend: we benefit immediately from the trip, but the consequences are deferred and shared amongst the global population.

Many studies have quantified footrprint of individuals, organisations and nations in various forms, and concluded that we are indeed living beyond our means , e.g.(Wackernagel et al. 2002; MEA 2005).  However individuals lack quantitative guidelines for sustainable consumption: how many GHG emissions per capita globally would keep temperature rise to less than 2 oC, and what does this translate to in terms of personal energy usage, transport and air travel?

The purpose of this project is to quantify individual "quotas" which would enable people to make informed choices about how they can consume a sustainable share of the world's resources, and so directly address the tragedy of the commons.  Student research and PhD projects available.

Minimising greenhouse gas emissions from the concrete industry: identifying the right incentives, mechanisms and metrics

The concrete industry is major contributor to global greenhouse gas (GHG) emissions, and the largest consumer of resources globally.  The production of Portland cement, a key ingredient in concrete, accounts for approximately 80 % of GHG emissions associated with concrete.  The main pathway to reduce GHG emissions is to replace Portland cement with “supplementary cementitious materials” (SCM), which are waste by-products from other industries (O’Brien et al. 2009).  Common SCM include fly ash from coal-fired power stations, and blast furnace slag from the steel production (O'Moore and O'Brien 2009).  

Policies implemented to reduce GHG emissions from the concrete industry have sometimes produced perverse outcomes, either due to use of incorrect metric (e.g. SCM usage, rather than the reduction in Portland cement or GHG emissions), or providing incentives to source cement offshore (e.g. carbon tax on local but not imported Portland cement). 

The purpose of this project is to use analysis and modelling to identify strategies for GHG gas reductions from the concrete industry.

Collaborators: Liza O’Moore. Student research and PhD projects available.

Assessing eutrophication potential for management decision-making

Life cycle assessment (LCA) is a tool for comparing the environmental impact of different products or processes, and is widely used in decision-making and policy development globally.  The current method of assessing eutrophication potential in LCA is very simplistic.   The project seeks to better incorporate current scientific knowledge into Australian LCA models for waterways eutrophication.   Key questions include: How and when does the form of nutrients emitted to waterways (e.g. dissolved vs particulate, inorganic vs organic, ammonia vs nitrate) affect eutrophication potential? and Subtropical and tropical catchments are dominated by episodic events; how should eutrophication potential be assessed in these systems?   More generally, how can temporal variation in nutrient limiting-status be incorporated into simplified metrics?

Collaborators: Joe Lane, Paul Lant, Michele Burford Student research and PhD projects available. 

Dynamics of tropical topical floodplains

Floodplains cover large areas in Northern Australia, and represent regions of strong coupling between terrestrial, freshwater and marine systems.  Field measurements, remote sensing and modelling are integrated here to quantify the impact of seasonal inundation on floodplain productivity, and assess the likely impacts of climate change and flood regulation on floodplain productivity and associated ecosystem services.  

Collaborators: Michele Burford Student research and PhD projects available.

Teaching and Learning: 

2012 Developed and co-ordinated Introduction to environmental systems engineering CHEE2501

2011 BE/ME chemical-environmental program development

2006-present Heat and mass transfer CHEE3002

2003-2008 Taught Engineering analysis of environmental systems in Introduction to Professional Engineering ENGG1000

Teaching awards: Nominated for UQ Excellence in Teaching Award 2010-2012, Awarded EAIT Faculty Excellence in Teaching Award 2009, Awarded School of Engineering Excellence in Teaching Award 2008, received more than 30 Dean’s Commendations for effective teaching 2006-2012.

  • Joe Lane, PhD in progress, Life cycle assessment of urban water systems
  • Matthew Prentice, PhD in progress, The role of phosphorus in promoting cyanobacteria blooms in subtropical reservoirs
  • Emily Saeck, PhD 2012, Nutrient dynamics of coastal phytoplankton: the role of episodic flow events and chronic sewage discharges
  • Michael Kehoe, PhD 2010, Modelling of physical and physiological processes controlling primary production and growth in cyanobacteria
  • Dana Burfeind, PhD 2009, Caulerpa taxifolia growth dynamics in invasive and native populations


Key Publications: 


  • Saunders, M.I., Leon, J.P., Phinn, S.R., Callaghan, D.P.,  O’Brien, K.R.,  Roelfsema, C.M.,  Lovelock, C. E., Lyons, M.B.  and  Mumby, P. J. (2013) Coastal retreat and improved water quality mitigate losses of seagrass from sea level rise. Global Change Biology, in press
  • Saeck *, E.A., O’Brien, K.R., Weber, T.R and Burford M.A. (2013) Changes to chronic nitrogen loading from sewage discharges modify standing stocks of coastal phytoplankton.  Marine Pollution Bulletin, in press.
  • Burfeind, D.D., O'Brien, K.R. and Udy, J.W. (2013) Water temperature and benthic light levels drive horizontal expansion of Caulerpa taxifolia in native and invasive locations. Marine Ecology Progress Series, 472 : 61-72.
  • Brookes, J.D.,  O’Brien, K.R.,  Burford, M.A., Bruesewitz, D.A., Hodges, B.R. McBride, C. , and Hamilton, D.P. (2013) Effects of diurnal vertical mixing and stratification on
  • phytoplankton productivity in geothermal Lake Rotowhero, New Zealand. Inland Waters 3, 369-376.
  • Saeck*, E.A., Hadwen, W.D., Rissik, D.A., O’Brien, K.R. and Burford, M.A. (2013) Flow events drive patterns of phytoplankton distribution along a river-estuary-bay continuum. Marine & Freshwater Research, in press.
  • Kehoe, M., O'Brien, K.R., Grinham, A., Rissik, D., Ahern, K. S. and Maxwell, P. (2012) Random forest algorithm yields accurate quantitative prediction models of benthic light at intertidal sites affected by toxic Lyngbya majuscula blooms. Harmful Algae, 19 : 46-52. 
  • O'Brien, K, G.N. Ivey, D.P. Hamilton, A.M. Waite and P.M. Visser. 2003. Simple criteria for the growth of negatively buoyant phytoplankton. Limnology and Oceanography 48: 1326-1337.
  • Burford, M.A., Green, S.A., Cook, A.J., Johnson, S.A., Kerr, J.G., O’Brien, K.R. 2012. Sources and fate of nutrients in a subtropical reservoir. Aquatic Sciences, 74 1: 179-190.
  • O'Brien, K.R., Hapgood, K.P. 2012 The academic jungle: Ecosystem modelling reveals why women are driven out of research. Oikos, 121 7: 999-1004.
  • O'Brien, K., Hapgood, K. 2011 Part-time balance. Nature, 479 : 257-258.
  • O'Brien, K. R., Grinham, A., Roelfsema, C. M., Saunders, M. I. and Dennison, W. C. 2011. Viability criteria for the presence of the seagrass Zostera muelleri in Moreton Bay, based on benthic light dose. In: , MODSIM 2011: International Congress on Modelling and Simulation proceedings. Modelling and Simulation Society of Australia and New Zealand (MODSIM 2011), Perth, Australia, (4127-4133). 12 - 16 December 2011.
  • Hamilton, D.P., O’Brien, K.R., Burford, M.A., Brookes, J.D., McBride, C.G. 2010. Vertical distributions of chlorophyll in deep, warm monomictic lakes. Aquatic Sciences 72: 295-307.
  • O’Brien, K.R., M.A. Burford and J.D Brookes. 2009. Effects of light history on primary productivity in a phytoplankton community dominated by the toxic cyanobacterium Cylindrospermopsis raciborskii. Freshwater Biology: 54 2: 272-282.
  • O’Brien, K.R., J. Menache, L.M. O’Moore 2009 Impact of fly ash content and fly ash transportation distance on embodied greenhouse gas emissions and water consumption in concrete. Int. J. Life Cycle Assessment, 14: 621-629.
  • O'Brien, K.R., A.M. Waite, B.L. Alexander, K.A. Perry and L.E. Neumann. 2006. Particle-tracking in a salinity gradient: a method for measuring sinking rate of individual phytoplankton in the laboratory Limnology and Oceanography: Methods, 4:329-335.
  • O’Brien, K.R., D.L. Meyer, A.M. Waite, G.N. Ivey, and D.P. Hamilton. 2004. Disaggregation of Microcystis aeruginosa colonies under turbulent mixing: laboratory experiments in a grid-stirred tank. Hydrobiologia 519: 143-152.