On the map, zoom in and click on the dots to view underwater video at each site
Seagrass cover around Semaphore and Grange North have declined.
Seagrass cover around Barker Inlet and adjacent the Torrens are stable.
A number of sites are showing improvement in condition compared to previous monitoring in 2010 and 2011.
Area map
About the biounit
The Adelaide Metropolitan biounit was created from the Clinton biounit to capture the condition of the Adelaide metropolitan coastline. The biounit boundary extends along the most densely populated and urbanised section of the coast from Marino in the south to Gawler River in the north, out to the 5 m bathymetric contour and includes the Port River and Barker Inlet
The Adelaide metropolitan coast is a low to moderate wave energy environment where the wave energy generally increases further to the south of the biounit. The environment has been heavily impacted from terrestrial and industrial activities that have caused the loss of a considerable amount of seagrass, in some locations leaving only bare sand.
The Adelaide Metropolitan biounit receives stormwater runoff from numerous outlets along the coastline including the Torrens River and Barcoo outlet. Two large wastewater treatment plants at Bolivar and Glenelg discharge large volumes of treated wastewater into the Gulf. The Port River and Barker Inlet Estuary has large areas of shallow, warm waters with restricted flushing with Gulf waters. They tend to retain poorer quality water, maintain favourable conditions for algal growth and have an increased risk of environmental impacts. The Port River is heavily industrialised to allow shipping traffic for the import and export of goods for Adelaide.
Penrice Soda Products facility in the Port River closed in 2014. This was a large contributor to the nutrient enrichment for the Port River and Adelaide metropolitan waters.
Over the last 70 years, the cumulative impact of discharges have contributed to the degradation of the nearshore environment throughout the Adelaide metropolitan biounit with the loss of over 6000 hectares of seagrass and degradation of rocky reefs documented.
The Adelaide Metropolitan biounit was expected to be in Good condition based on the 2011 Aquatic Ecosystem Condition Report and the assessment of threats to the nearshore habitats.
In summary
The Adelaide Metropolitan biounit was rated as Fair during 2017. This score has decreased since 2011 where it was classified as Good, but this is likely to be due to natural variation with only small changes in condition that straddled the boundary between Good and Fair.
The biounit was largely stable since 2011, with most sites continuing to support sparse, patchy cover of seagrass. Two sites, Black Pole Inner and Grange, show increased seagrass cover compared to the previous assessment, while Semaphore Park Inner and Grange Nth have both decreased in seagrass cover.
Episodic high turbidity is likely to be still limiting condition throughout the biounit. Turbidity reduces light reaching seagrass leaves, which affects the health of seagrass and algae. Elevated turbidity also affects the aesthetic value of the beaches making them unattractive for swimmers.
In addition to turbidity, there are numerous symptoms of nutrient enrichment throughout the biounit, such as epiphytes growing on seagrass leaves and elevated nutrients in the water. These factors can all affect the condition of the environment.
Findings
Eight sites were monitored during 2017; 45% of the sites were seagrass habitat and 55% were unvegetated sand. In 2017, no reef was encountered.
Seagrass condition throughout the Adelaide Metropolitan biounit was considered to be 30 out of 100 and largely stable over time.
Seagrass at Barker Inlet, West Beach Inner, Grange and Glenelg were all degraded. While seagrass was dense at Semaphore Inner and Grange Nth, but cover has declined compared to monitoring in 2011. Black Pole Inner and Grange sites both showed an increase in seagrass cover compared the 2011 results.
Epiphytes are the algae that grow on seagrass leaves. When at high loads, epiphytes can impact the amount of light the seagrass receives and can result in death of the seagrass. Seagrass epiphyte loads often indicate nutrient enrichment from pollution. Seagrass epiphyte load was 11/100 for the biounit and was not greater than 25/100 for any site, however epiphyte load was highest at sites such as Semaphore Pk Inner, Torrens and Grange Nth where seagrass cover was also highest. Conversely, epiphyte load was lowest at sites with the least seagrass indicating that substrate may be influencing epiphyte growth.
In most sites, water column nutrients have reduced compared to the 2011 results, but Barker Inlet and Black Pole Inner both are elevated compared to the most open sites. These results suggest that the Barker Inlet and Port River are still affected by current or historical nutrient discharges in the region. While turbidity had decreased marginally across the biounit, the nearshore waters of the Adelaide coast were elevated, particularly north of the Torrens outlet where it may be restricting seagrass recovery.
Pressures and management responses
Pressures
Management actions
Nutrient load discharged (over several decades) by 2 wastewater treatment plants along the Adelaide metropolitan coast at Glenelg and Bolivar.
SA Water assess and undertake scheduled process improvement actions at wastewater treatment plants, with the aim to reduce environmental risk and ensure operations are compliant with EPA licence conditions. In addition SA Water has extensive recycled water systems and looks to expand these when opportunities arise that are economically viable. This helps to reduce nutrient loads.
Sediment and highly coloured runoff from the Adelaide Metropolitan stormwater entering nearshore marine waters.
The EPA through the Australian Government National Landcare Program funded Catchment to Coast project has been working with councils and community groups to install rain gardens that slow the release of stormwater and provide longer for sediment to drop out of the water. This project titled ‘Catchment to Coast focus for water quality improvement across urban Adelaide has implemented several strategies of the ACWQIP, including building community capacity and education to clean up stormwater and promoting greater use of water sensitive urban design in Adelaide. A partnership with Water Sensitive SA has helped to promote information and training for local councils, developers and community members in the construction and maintenance of rain gardens www.watersensitivesa.com
However, it is important to note that seagrass is slow growing and it takes a long time to recover from disturbance, so improvement in condition relative to these strategies may not be apparent for decades.
Maintenance dredging at boat harbors discharge turbid water containing high amount of dead seagrass into the nearshore waters
Dredging is a licensed activity under the Environment Protection Act 1993 and is regulated through conditions on licences requiring suitable management of dredge spoil and discharge water and that monitoring programs are in place.
Penrice Soda Holdings at Osborne contributed high nutrient loads (as ammonia) into the Port River over several decades. This nutrient enriched water has been transported into the nearshore marine waters of the Adelaide Metropolitan Biounit.
Penrice Soda Holdings facility in the Port River closed in 2014.
Observed Condition
Expected Condition