Bioavailable nutrients from sediment – applications towards reducing risk to the reef and enhancing gully remediation practice

Alexandra Garzon Garcia

Our research shows that sediments have the potential to generate considerable loads of dissolved inorganic nitrogen (DIN) as they move through rivers and in flood plumes within the Reef lagoon, which can stimulate freshwater and marine algal growth. These sediments may continue to generate DIN once deposited on the marine floor or resuspended.

The full impact of gully remediation on achieving Reef water quality targets can be ascertained by including nutrients from sediment in addition to sediment quantity in gully prioritisation and catchment modelling. We show that the type of vegetation used in remediation as well as the soil amendment type, influences downstream particulate nutrient bioavailability. Monitoring gully nutrients at remediation sites is essential for developing a stacked sediment and nutrient Reef Credit method in grazing catchments. The methods developed for assessing bioavailable nutrient contributions from sediments and soil materials, and the database of bioavailable nutrients from sediment already developed in some catchments, can now be used to inform prioritisation, and assess the risk from this source of nutrients to the Reef.

This research highlights the need to progress the inter-operability of the paddock-to-reef and marine models to account for this source of nutrients and to monitor them at end-of-catchments.