Groundwater Insights Reveal Nutrient Pathways Along Ningaloo Reef

In a detailed field campaign reported on 18 June 2026, researchers from the Australian Institute of Marine Science (AIMS) and the Leibniz Centre for Tropical Marine Research surveyed groundwater and surface water along the Ningaloo coast in Western Australia. The work, conducted under the Blue Carbon Seascapes Project, involved sampling 33 groundwater sources and 54 ocean surface locations across the northern and southern reaches of the reef.

Field teams, including Dr Kay Davis, Frederike Kunz and Michael Heldsinger, collected water from wells, bores and directly from the shoreline. Samples were pumped ashore for laboratory analysis, where parameters such as salinity, temperature, depth, dissolved oxygen, pH and radon concentrations were recorded. Radon, a known tracer for groundwater, helped distinguish subterranean inputs from surface water mixing.

Results revealed a clear north‑south contrast in groundwater dynamics. In the northern Cape Range, the aquifer is largely unconfined, allowing relatively free flow of groundwater towards the reef. This pathway carries dissolved nutrients and carbon that can support reef productivity but may also influence water quality if inputs become excessive. By contrast, the southern Ningaloo sector is underlain by deeper groundwater with limited hydraulic exchange, suggesting a more isolated influence on the adjacent marine environment.

The timing of the survey coincided with the passage of Cyclone Narelle. Heavy rain associated with the cyclone increased the volume of groundwater reaching the reef, as indicated by elevated radon levels and shifts in measured salinity and temperature. These observations underscore the sensitivity of groundwater‑derived fluxes to extreme weather events and point to the need for flexible monitoring frameworks that can capture episodic changes.

Data gathered during the campaign have been used to develop a groundwater flow model for the Ningaloo region. The model integrates measured hydraulic gradients, aquifer characteristics and tracer data to predict how water moves from land to sea under varying climatic conditions. By feeding this model into the broader Blue Carbon Seascapes Project, managers aim to quantify the capacity of marine soils and canopy‑forming seaweeds to store carbon delivered via groundwater.

The findings are intended to inform decision‑makers responsible for reef management and coastal planning. Understanding the magnitude and pathways of nutrient and carbon delivery can guide strategies to maintain water quality, support blue‑carbon sequestration and enhance the resilience of coral communities against stressors such as warming and acidification.

Future steps outlined in the report include integrating the new groundwater data set with existing monitoring networks, refining the flow model with additional seasonal sampling, and assessing the potential for marine soils to act as carbon sinks within the Ningaloo marine park. The collaborative effort also seeks to communicate results to traditional owners and other stakeholders, ensuring that knowledge of groundwater‑reef interactions contributes to broader conservation objectives.