Abstract: Water quality of the Great Barrier Reef (GBR) is determined by a range of drivers such as river flow, catchment condition, winds and waves. Observational studies have shown the impact of changing nutrient and sediment loads from the GBR catchments on water quality. Disentangling whether these impacts are caused by natural loads from undisturbed catchments or anthropogenic loads from agricultural and urban land-use changes is critical to water quality management on the GBR. This talk uses simulations of the eReefs coupled hydrodynamic-biogeochemical marine model forced by a process-based catchment model: Dynamic SedNet. Dynamic SedNet simulations can calculate natural and anthropogenic loads separately, meaning we can determine their relative impact on a range of marine water quality variables. We simulate reductions of anthropogenic loads to address: (1) the proposed Reef 2050 Water Quality Improvement Plan targets, and (2) application of industry-specific Innovative, Best-Practice and Minimum-Standards catchment management standards. The ability of the modelling system to isolate the impacts of anthropogenic load reductions allows us to optimise catchment management for the greatest benefit to GBR water quality. This talk will provide an overview of the modelling system with its strengths and weakness, while remaining relevant to the broader coral reef science community. Simulations are publicly-available for use in relevant research including on COTS outbreaks and coral community dynamics.

Biography: Mark Baird is an aquatic scientist who uses observations and numerical models to study estuarine and marine ecosystems. He received an Undergraduate degree in Mechanical Engineering (USYD), a Masters’ degree in Chemical Oceanography (University of Hawaii), and a PhD in Biological Sciences (University of Warwick). He has worked as a researcher and educator at the UNSW, UTS and CSIRO, and became an ACRS Fellow in 2020. He has published works on coral-symbiont dynamics, estuarine ecology, plankton population dynamics, salp blooms, ocean acidification, physical oceanography, marine bio-optics and ecosystem modelling. Mark leads the CSIRO Coastal Biogeochemical Modelling team that developed key components of the eReefs marine modelling system that is being used to estimate the water quality properties of the GBR, and to optimise the reduction of loads of sediments and nutrients to improve water quality. His passion is to develop state-of-the-art models that synthesise the data available from field and laboratory studies to optimise environmental management strategies.