Jussieu Nearshore Marine Biounit
2010 Aquatic Ecosystem Condition Report
Condition overview
Observed Condition
Expected ConditionKey points:
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On the map, zoom in and click on the dots to view underwater video at each site.
- Seagrass habitats around Proper Bay, Spalding Cove and Thistle Island were dense and largely intact.
- Seagrass around Boston and Louth Bays were generally degraded.
- Almost all habitats monitored throughout the biounit were under stress from epiphyte growth. It is possible that seagrass could be lost if this stress continue.
- Large nitrogen load entering some areas of the biounit during autumn, it is unclear whether these nutrients are from natural upwellings or anthropogenic in origin.
Area map
About the Jussieu Biounit
The Jussieu Biounit extends from Cape Catastrophe including Thistle Island through to Salt Creek north of Tumby Bay (see the map). The shoreline of the Jussieu biounit is primarily orientated in an easterly direction resulting in the biounit being dominated by offshore breezes and low wave energy (Edyvane 1999 – see further information)
The Tod River flows into the southern end of Louth Bay when there is sufficient rainfall and drains a large catchment of predominantly agricultural land carrying nutrients and sediment from the catchment into the sea. EPA monitoring indicates that the Tod River is in Fair to Poor condition and water quality is likely to be degraded when flowing to the sea. It is also possible that soil carried by wind from agricultural lands may also be affecting water quality. The southern part of the biounit is adjacent to large areas of National Park and there are numerous offshore islands which have been cleared but currently there is little development on them.
The City of Port Lincoln is located in the south west of the biounit and is home to approximately 14,000 people. Port Lincoln the largest town on the Lower Eyre Peninsula, with numerous industries including the wastewater treatment plant at Billy Lights Point and the shipping and fishing industries centred around the wharves. The waters in this region are used extensively for aquaculture, including inshore waters within Louth & Boston Bays there is kingfish (Seriola lalandi) and mussel (Mytilus galloprovincialis) aquaculture. The deeper offshore waters adjacent both Port Lincoln and Louth are heavily used for the aquaculture of southern bluefin tuna (Thunnus maccoyii). There are also several land based aquaculture facilities rearing abalone (Haliotis laevigata) discharging large volumes of water into the sea near Point Boston.
The Jussieu biounit has large areas of shallow, warm waters which have reduced flushing. This is likely to result in favourable conditions for algal grow that could increase the biological effects of excess nutrients.
There are very large nutrient inputs into Spencer Gulf from deep offshore waters. These upwellings bring cool nutrient rich water into the biounit during late summer and autumn. The role these nutrients play in ecosystem condition when compared to anthropogenic sources of nutrients is currently unclear.
The Jussieu biounit was expected to be in Fair condition, based on an assessment of threats to the nearshore habitats.
Summary
The condition of habitats in waters between 2 – 15 m deep throughout the Jussieu biounit was assessed based on monitoring data collected during autumn and spring 2010. There are large areas within the biounit that are deeper than 15 m which are not included as a part of this assessment.
The Jussieu biounit was observed to be in Good condition. In some areas there were dense and intact seagrass meadows while in other areas the habitats were degraded. Throughout the biounit there were many areas that were under significant stress due to nutrient enrichment which 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 23 sites were monitored during autumn and spring in 2010 to assess the condition of the biounit; 62% of the habitats monitored were covered in seagrass, while 36% were covered in unvegetated sand. There was only a small amount of rocky reef or small algae encountered in the sites assessed.
Seagrass coverage throughout the biounit was variable. Some areas had dense and continuous seagrass meadows, particularly in Proper Bay and Spalding Cove. While in other areas the seagrass was very sparse or patchy and generally in a degraded condition such as in Boston and Louth Bays.
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.) during spring which all suggests excess nutrients throughout the biounit.
There was a seasonal difference between autumn and spring in the nutrient concentrations and the water clarity, but the most distinctive difference was in the ratio between nitrogen and phosphorus which can be used as an indicator of nutrient enrichment. Sites throughout Boston and Louth Bays had very high ratios particularly during autumn suggesting a large input of nitrogen into these bays detected during autumn.
These findings suggest that the nearshore marine habitats in parts of biounit are under stress due to nutrient enrichment, which if sustained over time could result in habitat loss. If habitats are lost this can impact on the productivity of fisheries, 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 |
|---|---|
| The cumulative effect of intensive sea cage aquaculture contributes high nutrient loads into the nearshore marine waters |
The South Australian Research and Development Institute (SARDI) is preparing a report titled “Carrying Capacity of Spencer Gulf: Hydrodynamic and Biogeochemical Measurement, Modelling and Performance Monitoring”. This will investigate the transport and fate of nutrients within this region which can be used to manage the location and management of sea cage aquaculture throughout the Lower Spencer Gulf. Integrated Multi-Trophic Aquaculture (IMTA) has been proposed in the zone policy discussions particularly for the Louth Bay region could have the potential to reduce the overall nutrient load discharged within this biounit (Primary Industries and Regions SA). The Aquaculture (Zones - Lower Eyre Peninsula) Policy 2013, Aquaculture (Zones - Arno Bay) Policy 2011 and the Aquaculture (Zones - Port Neill) Policy 2008 limits the maximum biomass of sea cage aquaculture animals that can be grown in the zoned area and is based on a carrying capacity model to determine the suitable amount of fish for each particular region without causing adverse environmental impacts (Primary Industries and Regions SA). 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:
Annual Environmental Monitoring Program (FEMP) Environmental Monitoring Program sampling is conducted by 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. |
| Nutrient loads discharged by the Billy Lights Point wastewater treatment plant | Until 1994, raw sewage was discharged via an outfall to Proper Bay. In 1994, SA Water commissioned the Billy Light Point wastewater treatment plant which significantly improved the quality of the treated effluent discharged to the marine environment. Since 2004, SA Water has further reduced nutrient loads to the marine environment by diverting a proportion of the treated effluent for reuse via the City of Port Lincoln water recycling scheme. This scheme provides water for irrigation on Council parks and reserves. |
| Natural upwelling of cold, nutrient rich water from the continental shelf, offshore from the mouth of Spencer Gulf also contributes to the nutrient load throughout the region in autumn |
The South Australian Research and Development Institute (SARDI) is preparing a report titled “Carrying Capacity of Spencer Gulf: Hydrodynamic and Biogeochemical Measurement, Modelling and Performance Monitoring”. This will investigate the source, fate and transport of nutrients within this region including natural upwelling events. Differentiation of upwelling derived nutrients, nutrients from anthropogenic sources, nutrient cycling in sediments, and phytoplankton are all issues that need further resolution to manage nutrient enrichment in Spencer Gulf. |
| Stormwater runoff from the Port Lincoln area, discharging nutrients and sediments to the nearshore marine waters |
The City of Port Lincoln are undertaking the preparation of a Stormwater Management Plan (SMP) for Port Lincoln. The SMP includes a number of catchment specific objectives which include water quality improvement, which covers the area of nutrient export. The SMP includes a number of strategies (some of which are still subject to further design development to confirm their viability) to meet the objectives. The two main strategies that are likely to reduce nutrient discharges to Boston Bay are:
The SMP also recommends the implementation of water sensitive urban design and the retention of the existing natural gullies within the Township (to encourage infiltration and vegetative filtering) which will assist in improving water quality and minimising stormwater flows and hence minimise nutrient loads. The City of Port Lincoln are also pursuing the implementation of Water Sensitive Urban Design (WSUD) principles to enable stormwater run off to be filtered prior to discharge into the marine environment. First example completed was a 150m2 filtration basin constructed at Gawler Terrace, Port Lincoln. It filters stormwater collected off approx. 9.5 Ha of residential area through heavily planted reeds and sedges. This allows pollutants and sediments to settle out prior to flowing into Boston Bay. It was jointly funded between the City of Port Lincoln and the Eyre Peninsula (EP) NRM Board. Another example is a series of drainage swales constructed in Dennis Westlake Reserve to achieve the same results. The City of Port Lincoln have since received extra funding through the EP NRM Board to do more WSUD work at an existing stormwater detention basin at Bethany Court, Port Lincoln. This is an existing detention basin several kilometers off the coast but ultimately the overflow from this basin eventually reaches the coast. We are aiming to keep more of the water upstream through the use of reed beds and passive irrigation to minimise how much water actually makes it all the way down the water course. The District Council of Tumby Bay Council is about to commence a Stormwater Management Plan for Tumby Bay, an objective of which will be to minimise stormwater impacts of existing and future developments on marine and coastal environments. This work is jointly funded by Council, the Stormwater Management Authority and the Natural Disaster Mitigation Program, and the EP NRM Board is a key stakeholder and have been involved in early project scoping. Again, I would be glad to receive any information the EPA may have on the specific impact of stormwater runoff on this marine environment that could inform this work. |
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Failing and/or high density of onsite wastewater treatment (septic) systems in some coastal towns. Overflowing septic systems contribute nutrients to nearshore marine waters through shallow sub-surface or occasional overland flows. |
The Tumby Bay township has a Community Wastewater Management Scheme (CWMS) which collects and treats all residential and commercial areas of the township (District Council of Tumby Bay). On site disposal is limited to a relatively small number of properties on the outskirts of the township, generally well away from the coast. All new dwellings within the township boundary are required to be connected to the CWMS. |
| Todd River transports agricultural runoff with elevated nutrient and sediment loads into nearshore marine waters of Louth Bay |
The Eyre Peninsula NRM Board promotes managing land to improve water quality. This includes incentives for:
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| Fish processing facilities discharge nutrient rich effluent into the nearshore marine waters of Proper Bay | The EPA is currently working to ensure that all land based fish processors in the Port Lincoln region cease the discharge of untreated wastewater to the marine environment. The EPA will be working with the industry involved, as well as the City of Port Lincoln, regional development board, and other government agencies to achieve compliance with the Environment Protection (Water Quality) Policy 2003 requirement that all fish processing facilities incorporate a wastewater management system and do not discharge to the marine environment. |
Further Information
- Download the 2010 habitat and water quality data
- Download the Methods Report for the nearshore marine ecosystems monitoring, evaluation and reporting program.
- Edyvane, K. S. (1999). Conserving Marine Biodiversity in South Australia - Part 2 - Identification of areas of high conservation value in South Australia, Primary Industries and Resources SA, South Australian Research and Development Institute Aquatic Sciences. SARDI (Aquatic Sciences).
- Fletcher, W.,J. Chesson, J., Fisher M., Sainsbury, K.J., Hundloe, T., Smith, A.D.M. and B. Whitworth (2002) National ESD Reporting Framework for Australian Fisheries: The 'How To' Guide for Wild Capture Fisheries. FRDC Project 2000/145, Canberra, Australia. 120pp.
