Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2023

Evaluating the Interactive Effects of Climate Change and Chemical, Physical and Biological Stressors on Nearshore Coral Reefs: A Case Study in the Great Barrier Reef, Australia  (#95)

Sophie Mentzel 1 , Paul J van den Brink 2 3 , Kevin Brix 4 5 , John Carriger 6 , Jannicke Moe 1 , Rory Nathan 7 , Pamela Noyes 8 , Jason Rohr 9 , Julie Verheyen 10 , Jenny L Stauber 11 12
  1. Norwegian Institute for Water Research (NIVA), Oslo, Norway
  2. Aquatic Ecology and Water Quality Management Group, Wageningen University and Research , Wageningen, The Netherlands
  3. Wageningen Environmental Research, Wageningen University and Research, Wageningen, The Netherlands
  4. EcoTox, Miami, Florida, USA
  5. University of Miami, RSMAS, Miami, Florida, USA
  6. Land Remediation and Technology Division, Center for Environmental Solutions and Emergency Response, Office of Research and Development, U.S. EPA, Cincinnati, OH, USA
  7. Department of Infrastructure Engineering, University of Melbourne, Melbourne, Vic, Australia
  8. Integrated Climate Sciences Division, Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. EPA, Washington, DC, USA
  9. Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
  10. Laboratory of Evolutionary Stress Ecology and Ecotoxicology, KU Leuven, Leuven, Belgium
  11. La Trobe University, Wodonga, Vic, Australia
  12. Environment, CSIRO, Sydney, NSW, Australia

An understanding of the effects of the combined stressors of climate change (CC) and other anthropogenic stressors e.g., chemical exposures, is essential for improving ecological risk assessments of vulnerable ecosystems such as the Great Barrier Reef (GBR). In the GBR, coral reefs are under increasingly severe duress due to CC associated with increasing ocean temperatures, acidification and cyclone intensities. Near-shore reef systems of the Mackay Whitsunday coastal zone are particularly at risk to CC stressors as they are also being impacted by other anthropogenic stressors, including chemical, nutrient and sediment exposures associated with more frequent and large rainfall events that increase runoff of contaminated waters. 

 To illustrate how CC can be incorporated into ecosystem risk assessment frameworks, we first developed a conceptual model. Thereafter, we illustrated interactive effects of climate variables and the herbicide diuron on coral endpoints using an adverse outcome pathway (AOP) approach. This informed the development of a Bayesian Network (BN) to quantitatively compare the effects of historic (1975-2005) and future climate on inshore hard coral bleaching, mortality, reproduction and cover. We examined climate scenarios based on an ensemble of 16 downscaled models representative of current climate conditions and future climate conditions based on medium and high carbon emissions for two thirty-year periods: 2025-2055 and 2070-2100. In the BN model predictions, stressors included cyclones, temperature, ocean acidification, total nitrogen, the herbicide diuron, sediments, macroalgae overgrowth and Crown of Thorns Starfish (as an example of a coral predator).  Climate stressors had a greater impact than catchment-related stressors, with projected increases in coral bleaching and coral mortality under all future climate scenarios. This modelling exercise can support the identification of risk drivers and thereby assist in the prioritisation of management interventions to build reef resilience for the future.