Barker Inlet and Port River Estuary
The estuary is a natural area, on the edge of a city, hosting a busy port.
Location
The Barker Inlet and Port River Estuary extends from St Kilda to Port Adelaide, and is just 14 kilometres from the centre of Adelaide.
It includes the Port Adelaide River and Barker Inlet, which wrap around Torrens and Garden Islands.
The interconnected creeks and channels link the Gulf St Vincent and lands to the south and east (including the Barker Inlet wetlands). In their natural state they are lined by mudflats, mangroves, and saltmarshes (samphires) – many of which still survive today.
Estuaries are where fresh water from the land (via streams and drains) mixes with salt water from the ocean.
The Barker Inlet and Port River Estuary however, has much in common with a marine bay, as many areas receive considerably more water from the ocean than from land – especially since changes to the flow of the River Torrens in the early 1900s and West Lakes in the 1970s.
Tides have a big influence on the estuary, affecting everything from fish movement to the distribution and health of the mangrove forests. Inflows come from the north, via Outer Harbour, and the south, via West Lakes – which draws water from near Grange.
Major Features
The vegetation in and adjacent to the estuaries provides ‘services’ to nature and humans alike.
The ‘services’, sometimes referred to as ‘ecosystem services’, include food, shelter, filtering to improve water quality, the stabilisation of foreshores, and even the sequestration (storage) of carbon.
The Barker Inlet and Port River Estuary provides an important natural environment, which is recognised by several protected areas, including reserves under several different Acts of Parliament:
• Adelaide International Bird Sanctuary
• Barker Inlet - St Kilda Aquatic Reserve
• Gulf St Vincent Important Bird Area
Bird Island, at the entrance to Outer Harbour, is a recent feature of the estuary. It is based on spoil dredged from the harbour in the 1960s and 70s, and is now being extended through natural processes. Although small, it is valued as a bird colony, providing a roosting and feeding site for migratory and non-migratory birds, and a breeding rookery for seabirds.
The Port River and Outer Harbour remain the pre-eminent port for Adelaide. They are also home to a number of port and industrial facilities, including boat construction, cement works and power generation. Light industrial, urban and commercial centres are also adjacent much of the estuary.
History
The Kaurna are the traditional people of the area. They valued the abundant marine and bird life of the area, trapping and spearing fish, crabs and waterbirds, and gathering bird’s eggs, mussels, clams and oysters.
The Kaurna Heritage Trail site near the Ethelton mangroves has several interpretive signs which tell how Kaurna people made use of the natural resources of the area.
“There were mangroves down at Glanville and Port Adelaide before the wharves were built. Those mangroves were a source of food for the Kaurna people who lived there. They used to take lobsters (ngaultaltya) out of the Port River. Grandmother also told me they used to get shellfish – mussels (kakirra) and oysters. There were black swans (kudlyo) too (which we didn’t eat because he was protected) and they used to catch birds (parriparu) and fish (kuya)."
- Veronica Brodie “My Side of the Bridge”, 2002
Mangrove Walkway at Ethelton
In pre-European times mangroves fringed most of the Port River. The adjacent areas grew reeds, blue flax lilly and rushes. Uncle Lewis O’Brien described how the reeds were used:
“Around the Port River and the other waterways on our country there were reed beds. The Kaurna people made mats and nets and baskets and they were experts in their weaves…They made nets and stone fish traps as well as hunting nets for kangaroos and emus. And they would do things the Kaurna way. I remember my Aunt Gladys told me that Ivantji would say, ‘Always remember, you split the reed, my girl. You’ve got to split the reed when you weave!’ Kaurna people weave that way; others would use the whole reed. It’s like copyright. You could make something similar to another group; but you can never make it the same. So people could pick up a basket and know where it was made.”
-Kauwawa Lewis O’Brien, “The Port River” 2001
Native grasses have been extensively planted at the Lartelare Reserve which was established in 2009 to recognise and commemorate local Kaurna people, and in particular, Veronica Brodie’s great-grandmother Lartelare. Situated on the north side of the Hart Street (Jervois) Bridge, the park was a Kaurna campsite from prehistoric times until 1858 when it was relocated further south to the mouth of the Jervois Creek.
Lartelare Park is within the Newport Quays precinct and, during excavations for that project, numerous middens and discarded shells were uncovered. One monument in the park records the position of middens and tools buried beneath.
The relocation of Lartelare’s campsite in 1858 placed it closer to an oyster bed in the Port River recognised by both Kaurna and Europeans. Sheridah Melvin, in a research report f or the Lartelare Homeland Association named “Kudlyo the black swan dreaming: Veronica Brodie and the continuity of Kaurna history at Glanville and LeFevre Peninsula” (1994), writes:
“The very well known oyster bed at the mouth of the Jervois Creek formed part of Lartelare’s parents’ economic assets and is referred to in both the Aboriginal and the colonial history of Glanville, appearing on early maps of the river.” (P. 10)
South Australian Parliamentary Paper no 43 of 1885 shows the oyster bed marked with small dots to the south of the creek near the Jervois Bridge.
The Jervois Creek was subsequently filled in and the current bridge (built in 1969) was moved south over the oyster bed site. Oysters were still stored under the older bridge until 1917.
See more Information about Kaurna history in the Port River region and a photo of an excavated midden with discarded shells in Mudlangga to Yertabulti track and Yerta Bulti.
Some local Kaurna names include:
• Le Fevre Peninsula: Mudlangga lit (nose-place)
• Port Adelaide River area and estuary: Yertabulti or Yerta Bulti(land of sleep or death)
• Port Adelaide: Yartapuulti
• Port River dolphins: Yambo
• Black swan: Kudlyo
Monument for the middens and tools
SA Parliament Paper #43 (1885) showing oyster beds
With the arrival of Europeans, came the prompt development of Port Adelaide as a major shipping centre for the emerging colony of South Australia. The port was first used for shipping in 1837. Some aboriginal people stayed in Port Adelaide and worked as domestic servants, dock workers, or as weavers and repairers of nets and baskets etc..
The development of Port Adelaide included dredging thousands of tonnes of silt and mud from the Port Adelaide River, and land-fill to raise the height of adjacent residential and port areas above the reach of high tides.
Mangroves were removed and embankments made to protect new urban infrastructure. Over time, many of the surrounding wetlands and marshes, and the creeks draining from them to the estuary, were cleared, raised and drained.
Over several decades there have been major efforts to save and protect the remaining natural areas of, and adjacent to, the estuary, and to rehabilitate others. The development of the Barker Inlet Wetlands is an example, improving the natural environment and helping to recharge groundwaters and cleanse waters draining through them to the estuary.
Improvements in stormwater management and industrial processes, plus changes in the type of industries present, have further contributed to improvements in water quality in recent times.
Environmental Condition
All aspects of the estuarine environment are interlinked, but it can be useful to consider two key factors in overall ecosystem health – the quality of water in the estuary, and the condition of vegetation (and associated fauna) in and adjacent to it.
Water quality has improved markedly in recent years. Stormwater remains a key source of pollution to the Estuary.
Water quality suffered historically through ‘development’ of the port and surrounding areas, and industrial enterprises provided a continual threat, affecting measures such as:
• Nutrient enrichment and algal growth
• Microbiological contamination
• Contamination of sediments by a range of toxicants (e.g. heavy metals)
• Thermal effluent discharges
• Occasional very high loads of suspended solids, affecting turbidity
In more recent times strategic efforts across all tiers of government and industry have led to improvements in water quality, which are ongoing. Although the legacy of the past will linger, e.g. with contaminants held in sediments, it is reassuring to see environmental efforts being rewarded.
Stormwater/wetland management, the improved operation of industrial and waste treatment plants, and industry closure or relocation, have all been influential on the outcome.
The EPA undertook regular water quality measures until 2008. In December 2016, water sample results from the SA Health Department measured very low measures of bacteria making it possible for the Long Swim to resume in the Inner Harbour.
Water quality measures taken between December 2017 to June 2018 suggest that water quality has further improved over the intervening period of almost 10 years. Median and maximum values satisfy the thresholds for all water quality parameters during this time.
Long Swim Through Port Adelaide, December 17, 2017
Clearance, draining and land-fill have reduced the coverage of mudflats, mangroves and samphire (saltmarsh) in the estuary, since European settlement.
That, plus dramatic changes to the floor of the estuary (e.g. dredging) and reductions in water quality, would have resulted in changes to the vegetation and fauna of the estuary; such as a reduction of the area of seagrasses and the loss of shellfish reefs.
Areas of natural habitat not under some form of protective tenure must be considered at risk.
Rising sea levels pose a modern risk to the estuary and many surrounding areas, through inundation, shoreline erosion, and the further loss of mudflats, mangroves and samphire.
In the Port Adelaide area, the rises are due to both land subsidence and to global influences raising sea levels. In 2014 tide gauging in the Western Adelaide region has found sea levels to be rising at a rate of 2.06 millimetres per year and 2.08 millimetres per year at the Inner Harbour and Outer Harbour areas respectively
Estuarine fringe vegetation will be at most risk in areas where there is no opportunity for it to migrate inland, or when the rate at which it can migrate is less than the rate of sea level change.
The realities of that risk are apparent at Mutton Cove, after the seawall was breached by a major storm in May 2016. While Mutton Cove was predominantly samphire previously, with a tidal creek fringed by mangroves, it is now regularly inundated by the Port River. Most of the samphire has died and the area has become a mangrove forest. While the area was mangroves originally, the more diverse vegetation of samphires has been lost from this area.
Rising sea levels are likely to also compound problems with flooding and stormwater management in low-lying urban and industrial areas.
Ecology
The waters, intertidal zone, and adjacent lands of the Estuary are part of an integrated natural system.
Collectively the area is important environmentally as a nursery for fish and prawn species, a rookery, feeding ground and breeding location for resident and migratory birds, and a sanctuary for dolphins. The ecosystem helps stabilise the seabed and shorelines and contributes to improved water quality.
For the sake of simplicity, the areas ecology will be described in components, but the interactions between components – and the estuary and adjacent seas and other lands - are critical to the Estuary’s value.
In the Torrens Island Biodiversity Action Plan, Sarah Telfer reports that the estuary contains the largest area of mangrove forest, shallow seagrasses and mudflats in Gulf St Vincent.
Sheltered conditions and good light penetration create very high levels of plant and animal production making them prime contributors to the ecology of the gulf and major nursery habitats for juvenile species of commercial fish and crustaceans; particularly juvenile Western King Prawns and King George Whiting.
Simon Bryars reported extensively on the ‘Nearshore marine habitats of the Adelaide and Mount Lofty Ranges NRM region: values, threats and actions’ in 2003, and that report is the source of much of the following information.
Aquatic Zone
The bed of the Port River and shipping channel consists of sand and soft sediments that are predominantly bare but sometimes with a cover of invertebrates or macro-algae (including introduced Caulerpa species), and some seagrasses.
Barker Inlet is dominated by a mosaic of different seagrasses, predominantly Posidonia and Zostera.
Seagrasses stabilise sediments, fix carbon, provide a substrate for invertebrates which are eaten by fish and crabs, habitat for many small or juvenile fish, and are eaten by some molluscs and sea stars. They help maintain water quality and are a foundation to food webs.
Intertidal and shallow subtidal seagrass and sand habitats around Torrens Island support a high diversity of fishes and invertebrates, with 56 species identified during a 10-year study of the Port River-Barker Inlet system.
Many of these species are important to commercial and recreational fisheries, and many of the individuals sampled were juveniles; providing further evidence that the area is a ‘nursery’ for fisheries species.
A 2008 study listed 64 fish species for the Port River-Barker Inlet estuary.
A pod of about thirty bottlenose dolphins live in the Estuary, and many more visit the area each year.
Seagrass around remains of Dorothy H Sterling - photo by Steve Duncan - https://stevenduncanart.com
Zostera seagrass in Barker Inlet from a kayak
Shellfish Reefs
Shellfish reefs were once abundant in the Estuary, stabilising the sea-floor, cleansing the water as they filtered out their food, and providing food and habitat for other aquatic species – as well as food for humans.
The reefs of native mud oysters (Ostrea angasi), cockles and razorfish (pinna) were all but destroyed by dredging, poor water quality, and over-fishing - and the distribution of seagrasses has also been affected.
Native oyster (Osrea angasi) norht of the breakwater
Pinna reef opposite RSAYS
Did You Know?
In pre-Colonial times, native mud oysters formed massive reefs in the SA Gulfs, extending for more than 1,500 kms; rivalling the extent of the Great Barrier Reef. Throughout Australia, oyster populations are now less than 1% of their pre-colonial extent.
Fast Facts, from Dominic McAfee and Sean Connell (The Conversation):
• A single mud oyster can filter 100 litres of water/day
• A 25 cm-square patch of oysters can host 1,000 individual invertebrates
• Oyster reefs stabilise the seabed and dissipate wave energy
• Oysters lock up carbon in their shells, becoming a carbon sink and helping offset climate change
Intertidal Zone
Extensive areas of saltmarshes and mangroves also occur in the system, particularly adjacent to North Arm, Angas Inlet, and Barker Inlet.
Birds, including Banded Stilts, Australian White Ducks, Sooty Oyster Catchers, Pelicans, Terns, Egrets, Herons and Sandpipers rely on this habitat for feeding and breeding.
A 2003 report listed:
• Twelve fish and six macroinvertebrate fisheries taxa for the tidal flat habitat of the Port River-Barker Inlet estuary
• Twelve fish and three macroinvertebrate fisheries taxa for the tidal creek habitat of the Port River-Barker Inlet estuary
• Eight fish and four macroinvertebrate fisheries taxa for the mangrove habitat of the Port River-Barker Inlet estuary
Elegant Parrots at Mutton Cove
The mudflats in the Estuary are home to many molluscs, worms and other invertebrates, which provide food for wading shorebirds, including migratory species that annually travel to and from the northern hemisphere.
Mangroves provide nursery habitat for fish, shelter and nesting sites for birds, and help stabilise shorelines, as well as being habitat for invertebrates.
The mangroves on Torrens Island provide the Little Egret and Rufous Night Heron one of their few breeding areas in South Australia.
A simplified description of a marine foodweb (below) shows the importance of mangroves and seagrasses to a healthy marine ecosystem.
If shellfish reefs were re-established, they would play a equivalent foundation role to that of seagrass and mangroves, adding to the health of the whole ecosystem.
Simplified food web of Gulf St Vincent, from Shepherd et al, 2008 (Marine Parks Scientific Working Group)
Adjacent Lands
Samphire flats may be in the upper reaches of the intertidal zone or in low-lying, saline areas adjacent to them.
Samphire saltmarshes provide high-tide feeding and roosting areas for a wide range of bird species, including migratory species, as well as important breeding habitat for resident shorebird species. They also help stabilise foreshores.
Reptiles (lizards and skinks), crabs, and an array of insects and other invertebrates can be found in the marshes.
Carpobrotus rossii in Mutton Cove
Artistic Representations
The environment and history of the Port River and Barker Inlet Estuary stir emotions at many levels.
It is a haven for passive recreation such as bird watching, fishing and kayaking, while artists and photographers draw inspiration from the area. They use their work to express their feelings and inspire others.
The Healing Mural
The Healing Mural is located at the Port Adelaide Visitors Centre.
An interpretive guide says Kaurna men and women are symbolised by footprints through the mangroves, along with kangaroo prints…The Aboriginal camp is one of several once located along the river, overlooking oyster beds.
Community Arts
A number of community arts groups, centres and events flourish locally, drawing upon the region and its ‘sense of place’.
Examples include:
The City of Port Adelaide Enfield Public Art Guide, pages 6 & 8, identifies artworks referencing Kaurna culture, the Estuary and marine life.
Mosaic mural celebrating Kaurna life, Outer Harbour Railway Station