Seagrass grows in 'meadows', and is critical to the underwater ecosystem, providing habitat for fish, improving water quality, and storing carbon.
Seagrass habitats can be found all along the coast of Western Australia, with significant seagrass communities in Shark Bay, Cockburn Sound, Geographe Bay, and the South Coast.
The seagrass habitat of Cockburn Sound experienced significant losses from the 1950s to the 1990s due to a notable increase in nutrients and pollutants from industrial activities in and around Kwinana. Since then, there have been concerted and widespread efforts to improve water quality in Cockburn Sound, and active restoration of seagrass habitat that is critical to species including snapper and blue swimmer crabs.
Westport’s design for the new port facilities and marine infrastructure at Kwinana covers four different marine zones which are Cockburn Sound, Owen Anchorage, Gage Roads and the northern Deep-Water Channel with seagrass in all four zones. Our planning has actively worked to avoid direct and indirect impacts to seagrass and adopt an avoid, mitigate restore approach to seagrass management.
As part of the WAMSI-Westport Marine Science Program, more than 4,000 hectares of seagrass has been mapped across the four marine zones that Westport’s design covers. This research has provided us with the best understanding we have ever had of the seagrass communities along this stretch of coastline and is helping Westport to avoid and mitigate impacts to seagrass through a number of strategies.
Direct impacts to seagrass habitat have been avoided where possible through the port design process. Following the mapping completed through the WAMSI-Westport Marine Science Program, the location of the port footprint was shifted one kilometre to the south of its original proposed location to avoid directly impacting (i.e. removing) key seagrass meadows in Cockburn Sound.
Based on the current design, we anticipate the new shipping channel will directly impact (i.e. permanently remove) approximately two percent of existing seagrass across three zones – Owen Anchorage, Gage Roads and the Deep Water Channel.
Westport’s detailed design phase will continue to identify ways to further avoid and minimise seagrass impacts to the greatest extent possible.
Seagrass can be impacted by dredging during port development. These kinds of impacts include stirring up sedimentation, resulting in a reduction in the amount of sunlight that can reach the seafloor. Through the WAMSI Westport Marine Science Program, research has been undertaken to better understand the thresholds for healthy seagrass.
Dredge management planning will include water quality monitoring during dredging to maintain conditions for healthy seagrass.
Westport is committed to significantly scaling up seagrass restoration in Cockburn Sound before and after the port development.
Westport has begun this process by bringing together seagrass experts, key restoration programs, technology, and the WAMSI seagrass research, to put Western Australia at the forefront of global seagrass restoration efforts.
OzFish’s community-led Seeds for Snapper program, the largest seagrass restoration program in Australia, has been provided with $500,000 in funding to support the program’s expansion as it works to restore Posidonia australis meadows in Cockburn Sound and Owen Anchorage.
Westport also funded a $230,000 Australia-first trial of pioneering robotic seagrass planting technology developed by Ulysses Ecosystem Engineering, which was trialled during the November 2024 planting season in Cockburn Sound.
The seagrass planting robot injects the seeds directly into the sediment, improving the rate of planting and likely germination of the seeds, as compared to the current manual methods of dispersal.
As well as mapping seagrass meadows along the Western Australian coast, the WAMSI-Westport Marine Science Program has undertaken a number of other seagrass related studies that has given us the best understanding of seagrass habitat in Cockburn Sound that we’ve ever had.
Research projects on seagrass include light and sediment tolerance thresholds and requirements for successful seagrass restoration, and these findings will help increase effectiveness of future seagrass restoration activities.
This research will support Westport’s dredge management planning, and its commitment to significantly scaling up seagrass restoration programs in Cockburn Sound.
The seagrass research will inform Westport’s environmental impact assessments that are currently underway with both the State and Federal environmental regulators on the proposed marine infrastructure, which the EPA will release for public comment in 2026.
