The Great Southern Reef extends south from Brisbane around the southern half of the Australian continent, which includes the coast off Wollongong south of Sydney.
The reef off Wollongong supports a diverse range of temperate marine plants and animals including fish relevant to commercial and recreational fishers. It is also where ships drop anchor while they wait to enter Port Kembla.
The challenge
Anchors can be big – cargo or freight ships use anchors that weigh several tonnes, plus hundreds of metres of steel chain that secure them to the ship. Anchors and chains can drag on the sea floor and damage the seabed environment, including plants and animals.
Operators of cargo ships waiting to enter Port Kembla had assumed the seabed was sediment. But local fishers were aware there were reefs in deeper water offshore, and surveys by the Royal Australian Navy about 20 years ago confirmed these reefs existed.
However, there were many knowledge gaps. No one knew what the potential risk to biodiversity was from ships anchoring in the area.
This offshore area is a big area to map. It’s only in recent years that technology, including multibeam echosounders, underwater cameras and sophisticated vessel tracking, has made it possible to know what seabed habitats or ecosystems exist and to see where ships are anchoring.
We first set out in 2014, with the University of Wollongong and NSW Department of Primary Industries (Fisheries), to learn about the distribution of reef and other offshore habitats. We used a combination of mapping technology from echosounders, sediment sampling and video techniques to map anchorage areas.
In 2018, we began working with the various port authorities to understand the impacts from ships anchoring in the area.
We’ve now mapped about 90 square kilometres of the seabed off Wollongong. This represents about one third of the total area used by ships that drop anchor near the port.
We’ve combined this seabed mapping research with 12 years’ worth of vessel tracking data. This has helped us learn how much anchoring was happening and where.
The project received support from the NSW Department of Climate Change, Energy, the Environment and Water, NSW Department of Primary Industries/Marine Estate Management Strategy, the University of Wollongong, NSW Ports and Port Authority NSW.
We found that 60% of the area mapped, to date, and used by ships to anchor off the coast of Wollongong is low-profile or flat reef with enormous biodiversity. This includes deep-water kelp, sponges, corals and fish.
Anchoring impacts on these deep-water reefs were significant. This research has helped inform a new approach to improve anchoring management and operations in this area.
Outcomes from this work include:
- clear evidence of how much reef was exposed to damage from ship anchors, including resident plants and animals
- demonstrated the need to better manage anchoring activities
- ships are now directed to circular anchorages which are designated areas, limiting further damage to reefs and biodiversity
- Port Kembla Port is embracing their stewardship role and improving the way ships operate in the marine environment
- reduced overall impact from anchoring and allowing some areas to recover.
'While the biodiversity seen here probably isn’t as high profile as in some other warmer parts of the state, it’s a special place. These temperate ecosystems are important. It’s the magnitude of how much reef there is out there, that is incredible. It’s pretty significant for this section of our metropolitan coastline,' said Tim Ingleton, senior scientist working on the project.
'Currently only a small proportion of Australia’s marine area is mapped. Close to the coast, it’s less than 10–12%. It’s important to understand our seabeds so we can know what’s there and protect its cultural and environmental value.'
Our scientists plan to continue mapping the area to provide 100% coverage for this section of the coast. Future monitoring of the areas that have been previously anchored will allow us to see if, and how quickly, they recover.
More information
- NSW Marine Estate Management Strategyopens a new window
- Review of offshore anchoringopens a new window
- SeaBed NSW dataset on the structure and composition of the seabed adjacent to our beachesopens a new window
- Squidle+ marine research images, videos and large-scale mosaicsopens a new window
- Offshore mapping research
- Marine protected areasopens a new window