Deriving ecologically relevant targets to meet desired ecosystem condition for the Great Barrier Reef: A case study for seagrass meadows in the Burdekin region

Catherine Collier

Led by: Dr Catherine Collier, JCU


Project Summary

This project will derive Ecologically Relevant Targets (ERTs) for sediment loads for the Burdekin basin and provide the seagrass desired state across the Great Barrier Reef (GBR) by: 1) defining seagrass desired state for the GBR; 2) calculating light requirements; and 3) calculating ERTs for terrestrially sourced sediment loads, using Cleveland Bay as a case study. Historical and new data collections will be compiled and used to derive ERTs via statistical models and eReefs Relocatable Coastal Model (RECOM), and the seagrass sub-model in eReefs will be used to test ERTs.


Project Publications
Final Report





Project Description

What problem the projects seeks to address and how it will do this

The Reef 2050 Plan requires ecologically relevant and measurable targets against which to assess progress towards meeting the plan’s outcomes and objectives. Load targets that protect ecosystem condition in the GBR are termed Ecologically Relevant Targets (ERTs) (Brodie et al. 2017). Ensuring these loads protect the GBR will require ecological benchmarks (‘desired state’). As a case study we are assessing sediment ERT’s using seagrass desired state in Cleveland Bay as the ecological end-point.

Developing desired state and ERTs for the entire GBR was beyond our initial scope, and was identified by key stakeholders as an important future direction for this research. We are now in a position to partially fulfil this request. The project extension will determine desired state for the GBR (seagrass species), as well as the environmental requirements for meeting this. This has significant application in setting ERTs, and reporting through programs such as  Integrated the Reef 2050 Monitoring and Reporting Program (RIMReP) and Outlook. This output will expand the range of end-users.

Project outcomes to date

This project is currently half-way through (i.e. 1.5 years), with phase one (desired state of Cleveland Bay) nearing completion and phase two (ERTs) recently initiated. Phase 3, the extension, will involve defining desired state and habitat requirements using the GBR seagrass data set. We have:

  • Developed a protocol for defining desired state (Milestone 5) using Cleveland Bay as a case study (Lawrence and Gaddish 2018, Collier et al, in prep),
  • Created a framework to determine GBR-wide desired state for seagrass by developing a preliminary habitat classification scheme (Carter et al, in prep),
  • Assessed data availability for defining GBR desired state (Udy et al. 2018),
  • Deployed light loggers for >1 year and started the validation of the eReefs bio-optical model, and

Initiated phase 2 of the project in which ERTs will be tested using eReefs and statistical modelling.

How the research will be undertaken, including what is in and out of scope

This project will assess ERTs for the Burdekin River using seagrass desired state as the ecological end-point. Desired state will then be determined for the entire GBR, enabling broader extension of our method for determining ERTs. This project is a desk top analysis, making use of historical and new data, statistical modelling and eReefs.

  1. Desired state has been defined for Cleveland Bay as a case study, based on historical seagrass data (2007-2017) using statistical models. With the extension of this project, desired state will be developed from the entire GBR seagrass dataset, building on the seagrass composite (Project 3.1), and adding biomass into the composite and four years of new data (2015-2018). Environmental requirements for GBR seagrass desired state will initially be assessed using statistical models including sediment (seagrass site data, Geoscience Australia, Seabed Biodiversity data), light (Fabricius et al. model), intertidal exposure (intertidal extent model (ITEM)), and bed sheer stress (eReefs 1km model) as these have been identified through the case study and previous research as important in defining desired state. These models will enable prediction of seagrass composition in data poor regions. Broader functions associated with the resilience of seagrass meadows (i.e. capacity to recover from an impact) will be assessed using the seagrass composite layer and a GBR-wide connectivity analysis (Grech et al. 2016, Grech et al. 2018). The scope will include the entire GBR where seagrass data exists. Through the habitat classification scheme and predictive models, we hope to define desired state for most of the GBR. Data availability has been summarized in Udy et al. (2018).
  2. Ecologically-relevant targets will include seagrass-specific water quality guidelines (light) and catchment-derived sediment loads from the Burdekin River. This requires validation of the eReefs bio-optical model, which is being assessed using historical and new (2016 – 2017) in-situ light data. eReefs predictions of seagrass distribution using the bio-geochemical model in RECOM will also be validated against seagrass monitoring data. Once validated, eReefs will be used to assess ERTs. ERTs will also be estimated from an alternative approach, using statistical models to quantify seagrass light requirements, and relate seagrass desired state to benthic light and associated environmental variables. These two different methods for calculating ERTs will provide a measure of uncertainty in ERTs.

Summary of how it is expected that the research will be applied to inform decision-making and on-ground action

  • Ecologically-relevant end of catchment load reduction targets for sediments, particulate nitrogen, particulate phosphorus and dissolved inorganic nitrogen are required, but were not included in the 2017 targets. The outcomes of this analysis will inform any future review of the Reef 2050 Plan targets in the Burdekin Basin, with a focus on sediments.
  • Ecological indicators and targets are needed to assess progress in meeting Reef 2050 Plan actions, targets and objectives. Desired state can be used to assess condition relative to targets in annual (e.g. MMP/RIMReP McKenzie et al. 2018), and longer-term outlook (Great Barrier Reef Marine Park Authority 2014), as well as in permitting (through provision of GBR-wide species distributions and biomass targets, as well as predicted species composition in data-limited regions).
  • Validated eReefs optical model and iteration of its parameterization through this project’s outputs, will enhance the confidence that end-users will have when using eReefs as a visualization and communication tool.
  • Desired state, and the environmental habitat requirements for meeting it can also be used to identify if restoration is needed following seagrass loss by identifying appropriate locations, species and communities, and environmental conditions suitable for seagrass growth.

Identified key seagrass resources can be used to inform the development of Environment Protection and Biodiversity Conservation (EPBC) Act 1999 policy guidelines for actions that may impact on marine turtles, dugong and seagrass habitat, and future iterations of the Dugong and Turtle Protection Plan and Recovery Plan for Marine Turtles in Australia..


NESP 2017 Research Priority Alignment

Improve our knowledge of cumulative pressures on environmental and social values of the Great Barrier Reef to determine more effective management actions (1.4).

Evaluate the practicalities of restoring connectivity to freshwater, coastal and marine ecosystems and the resilience of dependent species (1.6).

Understand trends in dugong and turtle populations, including breeding cycles and trends in seagrass and habitats. Develop better methods for the protection of important habitat for Dugong and turtles (3.2).

Combine existing indicators and monitoring programmes to develop a cost-effective integrated monitoring programme to support natural resource management, evaluate results and communicate trends (3.3).

Identify regionally-specific management interventions to achieve or maintain realistic desired states for tropical environmental, social, cultural and economic values (3.4).

Develop and implement better tools, including spatial information, to support the prioritisation of on-ground investments and interventions and asses their success (3.5).

Explore the opportunities for citizen science and Indigenous participation to improve tropical water quality awareness and outcomes (3.6).


Project Keywords

Sediment load reduction targets; Desired state; Water quality guidelines; Habitat; Reef 2050.


Project Funding

This project is jointly funded through JCU, UQ and the Australian Government’s National Environmental Science Program.