From exposure to risk: novel experimental approaches to analyze cumulative impacts and determine thresholds in the GBRWHA

Sven Uthicke
Led by: Dr Sven Uthicke, AIMS


Project Summary

Understanding cumulative impacts from multiple stressors will be critical for successful management of the GBR under the Reef2050 Plan. The project will produce experimental analyses of concentration-response relationships for selected species under broad, controlled envelopes of sediments, turbidity, nutrients, light, salinity and temperature. Based on new understanding of threshold exposure values, existing and new field data we will produce exposure maps for individual stressors and explore techniques to summarize those into cumulative exposure maps. Results will inform spatial and temporal assessments of ecological risks, and management opportunities for a range of activities in the coastal zones and inshore GBR waters.


Project Publications
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Science Day, 20th November, Townsville


Problem Statements


  • Cumulative impacts result from one or more stressors and their interactions can accumulate in time and space, posing a threat to ecosystem resilience. Cumulative impacts represent added ecological risks and potential surprises not accounted for in conventional risk assessments. Inshore environments in the GBR are high-risk candidates for cumulative impacts as they are exposed to land-based and coastal development activities impacting water quality in addition to regional and global pressures from climate change.
  • While reef managers recognize that cumulative impacts are an added risk dimension, large knowledge gaps exist in our understanding of the effect of individual stressors on key reef species, the interplay of local and global stressors and the way individual stressors combine into cumulative impacts.
  • There is wide acceptance that improvement in water quality will ‘buy time’ for reefs to acclimatize to a warming climate and increasing ocean acidification, yet it is still unclear whether the presently existing water quality targets, and derived ecologically relevant targets for water quality are set at the right level to achieve this outcome of increased reef resilience under climate change.
  • The new SeaSim facility in Townsville now allows us to investigate such complex interactions using sophisticated state-of-the art system controls. In SeaSim we can control cumulative exposures of sensitive marine organisms and processes under highly controlled yet environmentally relevant settings in an unprecedented way. We can therefore address and fill some of these key knowledge gaps on cumulative impacts far more efficiently than was possible in the past.
  • This collaboration has now started with 6-month NESP investment (Project 1.6) as a gap analysis and to develop the foundational framework for prioritization of end point measurements, and building on the risk priorities defined in GBRMPA’s Outlook Report.

How Research Addresses Problem

  • In this new project, we will investigate novel ways to assess combined risks on sensitive marine organisms and ecological processes, and will use concentration-response studies to determine critical exposure thresholds. We will use a two-pronged approach to conduct this study: Firstly, we will focus on the ecosystem health indicators measured by the MMP to score reef condition for the Reef Report Card, and second, we will complement this list of indicators with assessments of key eco-physiological processes including coral recruitment and reef metabolism that are likely to be vulnerable to change.
  • Our findings will facilitate and more realistically map GBR-wide exposures to acceptable and unacceptable risks for ecosystem integrity, in collaboration with eAtlas. The thresholds and exposure maps will support integrated monitoring and assessment of the adequacy of presently existing ecologically relevant targets for priority river pollutants.

Alignment with NESP Research Priorities

Priority 1G: Methods for assessing cumulative impacts from human activities and measures/approaches for ensuring a net environmental benefit.

As a secondary focus, the project also addresses: Priority 2A: Developing effective and costeffective catchment and marine water quality indicators, thresholds and sub-lethal healthindicators for key marine organisms and processes in support of the Reef Integrated Monitoring Program.


Project Keywords

Cumulative impacts; Environmental risk; Thresholds; Indicators.


Project Funding

This project is jointly funded through AIMS and the Australian Government’s National Environmental Science Programme.


Project Map

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