Restoring the Health of Minniribbie Creek
The iconic Minniribbie Creek is a vital stream system on the Lower Eyre Peninsula, originating as the outflow from Lake Wangary and discharging into Kellidie Bay then into the waters of Coffin Bay. It forms the downstream extent of Glengyle Creek, which flows into Lake Wangary. The creek’s surrounding landscape is primarily used for sheep and cattle grazing, cropping, and supports a large yabby and marron aquaculture farm in its lower reaches.
A Fragile Waterway Under Stress
Minniribbie Creek does not flow every year, but when it does, it carries large amounts of nutrients—primarily nitrogen, phosphorus, and carbon—into Kellidie Bay and Coffin Bay waterways. These excess nutrients, largely stemming from human activities, can significantly alter plant and animal communities, leading to water and sediment degradation.
One of the most noticeable effects is the excessive growth of algae and aquatic plants such as Ulva and Hincksia, which flourish in nutrient-rich marine waters. These species can clog creeks and lakes and smother seagrass habitats, ultimately disrupting delicate ecosystems.
The Impact of Rising Nutrient and Salinity Levels
Recent data shows salinity levels in Minniribbie Creek are the highest ever recorded—with readings of 21,748 mg/L in autumn and 12,221 mg/L in spring. This is a serious concern, as studies indicate that aquatic life is adversely affected when salinity exceeds 1,000 mg/L.
Salinity between 1,000–5,000 mg/L reduces biodiversity, impacting aquatic plants, zooplankton, and macroinvertebrate populations.
Freshwater species struggle to survive in salinity levels exceeding 3,000 mg/L.
As salinity increases, ecosystems change dramatically, favouring only salt-tolerant species while reducing overall biodiversity.
The Environmental Protection Authority (EPA) has identified significant damage to the ecosystem of Kellidie Bay, believed to be caused by high nutrient loads entering from Minniribbie Creek and stormwater runoff from urban development in the township of Coffin Bay.
According to the EPA, regular environmental monitoring has revealed extensive degradation of the marine ecosystem in both Coffin Bay and Kellidie Bay. Large areas of seagrass have died and been replaced by algae, leading the EPA to describe the ecosystem as being on the brink of collapse.
Seagrass plays a vital role in supporting a wide range of marine life and forms a critical part of complex aquatic food webs. The primary driver of the damage is nutrient enrichment from human activities, compounded by the bays’ limited water exchange with the open ocean. As a result, nutrients are accumulating faster than they can be flushed out, intensifying the ecological decline.
The Decline of River Red Gums
One of the most visible consequences of these environmental pressures is the decline of the River Red Gums (Eucalyptus camaldulensis) that once thrived along Minniribbie Creek. These magnificent trees, which can grow up to 45 meters tall and live for 500–1000 years, play a crucial role in the ecosystem.
Unfortunately, many of these trees have already died around Lake Wangary, and old River Red Gums along the Minniribbie system are also in decline. The high salinity levels are placing extreme stress on these trees, making them more vulnerable to wood borers and disease. As they weaken, they lose their ability to fight off infestations, accelerating their demise.
This loss is significant, as older River Red Gums develop hollows that provide essential habitats for marsupials, insects, and bird species. Their decline directly impacts the wider ecosystem, reducing shelter and food sources for many native animals.
A Call to Action
The health of Minniribbie Creek is at a critical tipping point. Without targeted intervention, its ecosystems will continue to deteriorate, potentially reaching a state beyond natural recovery.
To restore ecological balance, it is essential to slow the flow of water through the creek system. This can be achieved through the reintroduction of native grasses and the creation of ponds and other natural infrastructure along the creek’s length. Slower water movement creates optimal conditions for macroinvertebrates and micro-invertebrates to thrive — organisms that are fundamental to a healthy and functioning food web.
A reduced flow also encourages water to spill over the creek’s banks and infiltrate surrounding soils, helping to replenish groundwater reserves and suppress the rising saline water table. This process is vital for sustaining native vegetation, lowering salt concentrations, and improving overall landscape resilience.
Equally important is the removal of livestock from the creek environment. Establishing buffer zones where grazing is excluded will significantly reduce nutrient-rich runoff from manure, minimise erosion caused by soil compaction, and protect sensitive habitats.
Restoring Minniribbie Creek requires a coordinated, long-term approach. The active participation and commitment of all landholders along the creek are essential for implementing sustainable land management practices that benefit both people and the environment.
With shared awareness and collective action, we can rehabilitate Minniribbie Creek and ensure it continues to support native biodiversity and local communities for generations to come.