The Great Barrier Reef - A Global Icon

Managing nitrogen losses

A key focus of protection and recovery efforts are in the catchments and coastline adjoining the Reef. Both governments have pledged significant investments to improve water quality on the Reef and set targets with the aim of reducing suspended sediment, chemicals and nitrogen runoff by 2050. The Reef Water Quality Report Card 2017 and 2018 assesses the results of Reef 2050 Water Quality Improvement Plan actions.

Nitrogen losses from sugarcane cropping are a major threat to the Reef's health. Despite substantial investment in improving agricultural management practices, more improvement in water quality is needed to meet ecological targets for protecting the Reef's ecosystems. We use modelling to assess the economic and environmental impacts of nitrogen management strategies. We've also developed the 1622™ app which combines data from diverse sources to help sugarcane farmers optimise their crop management, reduce nitrogen losses and help protect the Reef. For the first time, farmers will have real-time information on key factors for growing sugarcane.

Managing sediment losses

The GBR catchments cover an area of over 423,000 km2, and cattle grazing is the dominant land use. Monitoring and modelling suggest that rangelands, primarily in the Burdekin and Fitzroy catchments, contribute approximately 75 per cent of the total fine sediment load that flows into the GBR lagoon. There, the fine sediments smother corals and seagrass beds, particularly closer to the coast and at the mouth of the large rivers. In big flood events, sediment plumes can even reach the outer reefs.

In response, CSIRO in collaboration with research organisations, land holders and regional Natural Resource Management bodies and with the help of funding from the Australian and Queensland governments has studied where the sediments come from, and how to manage grazing landscapes to reduce soil erosion and sediment loss. More recently, the focus has been directed at ways of effectively remediating gullies from where most of the sediment originates.

Ocean acidification

The term ocean acidification is used to describe the ongoing decrease in ocean pH caused by human carbon dioxide emissions, such as the burning of fossil fuels.

The oceans currently absorb approximately half of the carbon dioxide produced by burning fossil fuel. However, there is a cost; when carbon dioxide dissolves in water it (slightly) increases the water's acidity, or lowers its pH.

This affects the ability of marine creatures such crustaceans, corals and coralline algae to build their skeletons, endangering them significantly.

Coral bleaching

Bleaching is a stress response of corals.

As the water warms the symbiotic relationship between the coral and its zooxanthellae, a tiny marine algae that give corals much of their colour, breaks down turning corals pale, resulting in the tiny algae being expelled by the corals. Without these zooxanthellae, most corals struggle to survive, and can ultimately die if the warming is too severe or prolonged.

We continue to monitor the state of the Reef and contribute to weekly updates provided by the Great Barrier Reef Marine Park Authority. We use remote sensing, models such as eReefs (see below) and data visualisation to provide a picture of what is currently happening on the Reef and what will likely happen in the future. This further helps to prioritise funding initiatives and support water quality efforts.