Seagrasshabitats around Miranda, Mount Gullet and Ward Point were dense and largely intact.
Seagrass around Port Paterson, Blanche Harbour, Douglas Point, Baroota, and Fitzgerald Bay inner were generally degraded.
Almost all habitats monitored throughout the biounit were under stress from epiphyte growth on seagrass and opportunistic macroalgae indicating an excess of nutrients. It is possible that seagrass could be lost if this stress continues.
Elevated turbidity was evident at most sites in both autumn and spring, while there were also elevated nitrogen detected in the waters in some areas of the biounit detected in autumn.
Area map
About the location
The Winninowie Biounit occupies the far northern reaches of Northern Spencer Gulf; extending from Point Lowly on the Eyre Peninsula to Ward Point, on the Yorke Peninsula, north to Port Augusta at the top of the gulf. The orientation of the coast, relatively shallow depth and distance from the mouth of the gulf, typically results in low wave energies and restricted water movement which can result in areas with reduced flushing. This is likely to result in favourable conditions for algal growth that could increase the biological effects of excess nutrients. The geomorphology of the coastline is reasonably complex with numerous small bays and tributaries linking extensive mangrove flats to narrow, deeper channels where strong currents and extreme tides in excess of 3 m occur.
The City of Port Augusta is located in the northeast of the biounit and is the most northerly town on Spencer Gulf and has a population of approximately 7,330 people. The city’s sewage is collected and treated through two wastewater treatment plants (WWTP) located at Port Augusta West and Port Augusta East. The plant at Port Augusta East discharges effluent with high nutrient concentrations into the nearshore coastal waters near Hospital creek just south of Port Augusta. There are also a number of community waste management systems (CWMS) and individual septic systems to service satellite communities and shacks.
There are two large coal-fired power stations in Port Augusta; Playford and Northern power stations that discharge thermal effluent into the marine environment north of Port Paterson.
The waters of Fitzgerald Bay are used for the sea cage aquaculture of yellowtail kingfish (Seriola lalandii) (YTK). However, the amount of fish farmed at Fitzgerald Bay has significantly reduced in recent years.
Based on an assessment of threats to the nearshore habitats, Winninowie was expected to be in Fair condition.
In summary
The condition of habitats in waters between 2 – 15 m deep throughout the Winninowie biounit was assessed based on monitoring data collected during autumn and spring 2012. There are some small areas within the biounit that are deeper than 15 m which are not included as a part of this assessment.
The Winninowie biounit was observed to be in Fair condition. In some areas there were dense and intact seagrass meadows while in other areas the habitats were degraded with sparse and patchy seagrass and there were many areas that were under significant stress due to nutrient enrichment. This enrichment is likely to be causing excessive growth of algae on the seagrass leaves (epiphytes), which if prolonged, can result in seagrass loss over time.
It is important to note that this report assessed condition of the ecosystem and that these reports do not assess the suitability or quality of waters for aquaculture, food quality and fish health. For details about water quality affecting seafood quality please refer to the South Australian Seafood Quality Assurance Program (SASQAP).
Findings
A total of 10 sites were monitored during autumn and spring in 2012 to assess the condition of the biounit; 32% of the habitats monitored were covered in seagrass, while unvegetated sand accounted for 68% of the benthic habitat. No rocky reef was encountered in the sites assessed.
Seagrass coverage throughout the biounit was variable. Some areas had dense and continuous seagrass meadows, particularly in the waters adjacent to Miranda, Mount Gullet and Ward Point. While in other areas the seagrass was very sparse or patchy and generally in a degraded condition such as in Port Paterson, Blanche Harbour, Douglas Point, Baroota, and Fitzgerald Bay inner.
Throughout the entire biounit there were numerous indicators of nutrient enrichment. Seagrasses in many locations were covered in a thick covering of epiphytic algae and there were more frequent observations of snot weed (Hincksia sordida) and sea lettuce (Ulva spp.) which all suggest nutrient enrichment throughout the biounit.
There were some seasonal differences in the water chemistry sampled with turbidity and chlorophyll a being higher in autumn, whereas total nitrogen and total phosphorus were higher in spring.
Multiple indicators measured in this program suggest that the nearshore marine habitats in parts of this biounit are under stress due to nutrient enrichment, which if sustained over time could result in habitat loss and a decline in the AECR grade. If habitats are lost this can impact on the productivity of fisheries, nutrient assimilation, erosion and sand movement on beaches and wave attenuation and it can have a negative impact affect marine biodiversity.
Pressures and management responses
Pressures
Management responses
Nutrient loads discharged by the Port Augusta East wastewater treatment plant into the nearshore coastal waters just south of Port Augusta
The Port Augusta City Council operates a sewer mining wastewater reclamation plant (WWRP) which is used for irrigation of council open spaces. SA Water supplies the WWRP with low salinity wastewater and in 2012 assisted in doubling capacity of the facility by constructing a new pump station and connecting the Port Augusta Prison to the network. SA Water’s aim is to assist council maximise reuse, reduce effluent flowing to the Port Augusta East Wastewater Treatment Plant and reduce the concentration and load of nutrient discharges to the marine environment.
Stormwater runoff from urban areas discharge nutrient and sediment loads to the nearshore waters of the biounit
Since 2003, the Port Augusta City Council has required all new developments and significant civil upgrades to include Stormceptor technologies to treat urban runoff prior to marine discharge. This is an on-going initiative that will help reduce the quantity of nutrients and other pollutants entering the marine environment.
The cumulative effect of sea cage aquaculture can contribute high nutrient loads into the nearshore marine waters
When assessing an individual licence application there is a strict set of guidelines that applies a semi-quantitative risk-based assessment, based on a nationally accredited Ecological Sustainable Development assessment framework (Fletcher et. al., 2004), to determine the sustainability and outcome of each individual application. The integrity of the assessment process rests on understanding both the nature of the environment in which aquaculture is practised and the manner in which aquaculture interacts with or changes the environment that surrounds it. This includes assessment of approximately 40 possible risk events considered directly relevant to potential aquaculture influences, and applies them on both site and regional levels. PIRSA also apply guidelines to minimise environmental harm by excluding aquaculture over areas of seagrass, reef and macroalgae considered significant to local ecology.
Annual Environmental Monitoring Program (EMP) proformas are required to be submitted by all licence holders for each licensed site for each reporting year. These are reviewed (by PIRSA and EPA) prior to being sent out to licence holders to ensure appropriate information is being collected. Current data collected and assessed in EMP reports includes:
Site development and productivity
Feed and chemical inputs
Interactions with site infrastructure and marine vertebrates
Disease incidents
Debris incidents
Waste and refuse disposal
Annual Environmental Monitoring Program (FEMP) Environmental Monitoring Program sampling is conducted by the South Australian Research and Development Institute (SARDI). This program involves sampling sediment adjacent to actively farmed sites and using DNA profiling to measure changes in the benthic community compared to established control sites. PIRSA Fisheries and Aquaculture, the finfish industry and SARDI determine which sites are to be sampled each year. The same group has responsibility for any follow up action that needs to occur as a consequence of poor results through the 10-point FEMP plan of action.
Further information
Download the Methods Report for the nearshore marine ecosystems monitoring, evaluation and reporting program.