The Jussieu biounit extends from Cape Catastrophe, including Thistle Island, through to Salt Creek north of Tumby Bay (see map). The shoreline of Jussieu is primarily orientated to the east resulting in the biounit being dominated by offshore breezes and low wave energy.
The City of Port Lincoln is the largest town on the lower Eyre Peninsula, located in the southwest of the biounit. In 2021, its population was 14,404 people (2021 census), which is around 1200 less people than last monitoring period. Port Lincoln has large fishing, aquaculture and shipping industries centred around the marina and wharves. Sewage from Port Lincoln is treated at the Billy Lights Point wastewater treatment plant, which discharges nutrient-rich wastewater into Proper Bay. SA Water has recently upgraded sludge processing and handling facilities at the WWTP, as part of an agreed Environment Improvement Program with the EPA. These works were completed in late 2020, and included construction of an anaerobic digester and the decommissioning of sludge lagoons.
Parts of Port Lincoln are subject to significant stormwater flooding during high rainfall events. Poor quality stormwater enters the marine environment within Boston Bay during these events. There is also a risk of poorly managed sewerage discharges from marine vessels, for example in late 2020 a bulk carrier accidentally released 26 tonnes of sewerage into Boston Bay.
The Tod River flows into the southern end of Louth Bay when there is sufficient rainfall. The Tod catchment is largely agricultural land where runoff can transport nutrients and sediment to the sea. Over the last 2 years there has been higher than average rainfall in the area due to the climate driver La Nina. The EPA condition assessment in 2015 showed the Tod River was in a Fair to Poor condition and water quality is expected to be of Poor quality when flowing to the sea.
The waters are used extensively for aquaculture, including inshore waters within Louth and Boston Bays for Yellowtail Kingfish (Seriola lalandi) and mussels (Mytilus galloprovincialis). The deeper offshore waters are used for Southern Bluefin Tuna (Thunnus maccoyii). There are also several land-based aquaculture facilities growing abalone (Haliotis laevigata) which are discharging large volumes of water into the sea near Point Boston.
There are numerous embayments with shallow, warm waters which have reduced flushing with Gulf waters. These conditions result in favourable environment for algal growth that could increase the symptoms of nutrient enrichment.
The desktop threat assessment indicated the nearshore waters in the Jussieu biounit were expected to be in Fair condition.
It is important to note that this report assessed condition of the ecosystem and does 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).
In summary
Twenty sites were monitored in 2022. Jussieu biounit was observed to be in a Fair condition which is a drop in condition score from Good in 2016. To determine trend, only sites that were monitored in both 2022 and 2016 were compared to formulate the latest score. While the condition score of the biounit marginally changes from 2016, a number of ecological indicators in 2022 were trending down. The expert panel concluded the score to be Fair.
Overall, the Jussieu biounit experienced a 6% decline in seagrass cover. Louth Bay experienced the biggest change in condition, with a 42% reduction of seagrass percent cover from what was present in 2016. Boston and Proper bay are deemed to be in an unnatural state and are under pressures from nutrient enrichment.
Findings
The condition of habitats in waters between 2–15 m deep throughout the Jussieu biounit was assessed based on monitoring data collected during autumn 2022. There are some areas within the biounit that are deeper than 15 m which are not included as a part of this assessment. A total of 20 sites were analysed during autumn 2022 to assess the condition of Jussieu − 36% of the habitats monitored were classified as seagrass, 2.6% was reef and 61% was unvegetated sand.
In 2016, habitat data for Jussieu showed the biounit was in a Fair condition, the upwards trend in a number of ecological indicators and the score being within 1% of Good led the expert panel to upgrade the condition to Good. In 2022, 6 sites that were monitored in 2016 were excluded due to logistical constraints. Half these sites contained dense continuous meadows of seagrass, and one site had a relatively healthy reef system. When excluding these sites from the 2016 data set, the overall reef score of the biounit is impacted but there is little change to the seagrass percent cover. The change in reef condition score brings the 2016 data to well within the Fair condition score. Data from 2022 showed a decrease in seagrass percent cover across the entire biounit, a downwards trend in ecological indicators and reef systems remained stable.
Louth Bay
Since the 2016 monitoring period, 6 out of 8 sites within Louth Bay have declined in seagrass percent cover. Overall, the bay went from a total seagrass percent cover of 31% in 2016 to 18% in 2022, a 42% decrease. The biggest losses were seen in the apex species Posidonia at sites: Peake Point (m0114), which declined 60% from 2016 cover, Louth Island (m0111) declined 52% and both Point Boston (m0113) and Outside Bolingbroke (m0142) declined 37% from 2016.
The percent cover of Halophila spp. and Zostera spp. largely remained the same throughout the bay from 2016.
Epiphyte loads within the bay have dropped since 2016, driven by 2 sites; Peake Bay Inner (m0115) and Inside Bolingbroke (m0117). Excluding the data from these sites there is very little difference in epiphyte load between 2016 and 2022. The epiphyte load in this case is directly related to the amount of epiphyte on Halophila and Zostera species.
Observationally, the Halophila at Inside Bolingbroke and Peake Bay Inner was a much younger plant than in 2016, indicating that the mature plant died off sometime between 2016 and 2022 (potentially from the continual load of epiphyte which leads to increase risk of disease, reduced light availability and promotes blade breakage from hydrodynamic forces) and we are seeing younger plants established.
In 2018 a Tier 3 investigation was done to better understand the condition of habitats within Jussieu biounit. The data showed losses of the Zostera and Halophila at these sites from 2016. In the first round of AECR monitoring (2010), the sites contained none of these species of seagrass. The 2022 data again contained Zostera and Halophila. This demonstrates the ephemeral nature of these seagrass species over a relatively short amount of time.
Fp ratios of phytoplankton communities show that 3 sites within Peake bay (m0142, m0117, m0115) were borderline oligotrophic/mesotrophic. All other sites in Louth and Peake are in a mesotrophic condition and have increased from 2016.
Boston and Proper bays
Overall the seagrass percent cover stayed the same across the two bays, there were losses at some sites and gains at others. The presence of seagrass has completely disappeared in Rotten Bay (m0110), in 2010 there was more than 24% cover of Posidonia spp.. The habitat is now dominated by nutrient tolerant species such as; ascidians, invasive European fan worms (Sabella spallanzanii), holothurians (sea cucumbers) and microphytobenthos.
North Shields (m0105) had the second biggest loss of seagrass from 2016, with a 19.5% decline in Posidonia. Inside Boston Island (m0109) showed an 89% increase in Posidonia cover from 2016, although there are signs of growth within the meadows. This data could be subject to design variability as it was noted in 2022 that the deeper waters away from the island were dominated by small reds and fan worms, and more of the deeper waters were monitored in 2016 compared to 2022.
Epiphyte load has increased by 39% from what was present in 2016, current load is similar to the 2010 monitoring period. Phytoplankton community composition showed that 7 out of 8 sites were in a mesotrophic condition pushing up into eutrophic conditions. The high epiphyte loads, high Fp ratio in phytoplankton community composition and the large numbers of nutrient enrichment indicator species seen throughout the habitats indicate that these two bays are under pressure from nutrient enrichment.
Inside and outside Spalding Cove
Since 2010, seagrass cover inside and outside Spalding Cove has been reducing by about 20% with each monitoring period. Spalding Cove (m0118) shows pressures from nutrient enrichment with prominent large chlorophyll pigments within phytoplankton communities and >90% load of epiphyte on seagrass.
Cape Donington (m0122) experienced a significant loss in percent cover of Posidonia (20%), however epiphyte load has remained quite stable. Outside of Spalding Cove, at Thistle Island (m0124) there was a large increase of epiphytic growth on the seagrass at this site, associated with a reduction of larger chlorophyll pigment sizes present within phytoplankton communities.
At the time of sampling, water chemistry showed slightly elevated levels of total nitrogen with ranges from 100 ug/l–200 ug/l across the biounit which is well below ANZECC Guidelines for South Australian waters (1,000 ug/L total nitrogen) and slightly above the adopted value of 100 ug/L for South Central Australia. The adopted value has been used for modelling nutrient budgets in this biounit.
Pressures and management responses
Pressures
Management responses
Poor agricultural land management practices can result in sediment and nutrient rich runoff entering coastal waters
The EP Landscape Board administers the region’s Water Affecting Activity permitting program, which promotes best practice catchment management through the permitting process and ensure a minimum standard in relation to water affecting activities such as dam or watercourse crossing construction, draining or discharging water into a watercourse or excavations in a watercourse.
The Eyre Peninsula Landscape Board is working with landmanagers to fence off and restore riparian and coastal habitats increasing buffering capacity; and manage stock grazing pressure in riparian zones.
The EP Landscape Board have also been focusing on land care actions to help protect and improve temperate saltmarsh along these coastlines. Activities such as monitoring, revegetation, weed management, improving hydrological flows and removing marine debris are contributing to improving these threatened communities.
Stormwater runoff from the Port Lincoln area, discharging nutrients and sediments to the nearshore marine waters
District Council Tumby Bay- The council completed a receiving water risk assessment as part of Stormwater Management Planning (SMP) in 2014.Summary: Overall risks to the marine environments of the region from stormwater under existing conditions are low. Stormwater quality improvement works are currently assessed as low priority within the SMP, and implementation in the short term will be dependent on external funding. In 2019 the Council implemented recommendations from the SMP including the development of 3 x wetland retention basins, 2 x raingardens and 3 x infiltration basins to improve quality of stormwater discharge from the township urban areas.
Overflowing septic systems contribute nutrients to nearshore marine waters through shallow sub-surface or occasional overland flows.
District Council Tumby Bay - Tumby Bay Community Wastewater Management Scheme was commissioned in 1990. All township properties have been provided with approved, centralised effluent treatment and disposal.
Nutrient loads discharged by the Port Lincoln Wastewater Treatment Plant, located at Billy Lights Point.
Until 1994, raw sewage was discharged via an outfall to Proper Bay. In 1994, SA Water commissioned the Port Lincoln Wastewater Treatment Plant (WWTP), which significantly improved the quality of treated wastewater discharged to the local marine environment.
Since 2004, SA Water has further reduced nutrient loads to this marine environment by diverting a proportion of treated wastewater from the local WWTP, for reuse via the City of Port Lincoln water recycling scheme. This scheme provides water for irrigation on Council parks and reserves.
Additionally, in 2014, the wastewater treatment process aeration control was optimised to reduce the nitrogen concentration in marine discharges from the WWTP.
Over the past decade, SA Water has worked with the local aquaculture industry and the EPA to connect all land-based fish processing facilities identified by the EPA, to SA Water’s wastewater network for the safe and licensed disposal of fish processing waste. As of 2021, all facilities are now connected and this has resulted in the cessation of fish processing waste being discharged directly to the marine environment and is instead further treated at the Port Lincoln WWTP.
In parallel, SA Water has upgraded sludge processing and handling facilities at the WWTP, as part of an agreed Environment Improvement Program with the EPA. These works were completed in late 2020, and included construction of an anerobic digestor and the decommissioning of sludge lagoons that are no longer required.
This upgrade has resulted in improved environmental performance of the plant, through reduced odour and preventing seepage from lagoons to groundwater and the adjacent marine environment.
In early 2023, work began at the Port Lincoln WWTP to rehabilitate aerators which will maintain reliability of the plant’s treatment processes.
The cumulative effect of intensive sea cage aquaculture contributes high nutrient loads into the nearshore marine waters
The PIRSA Fisheries and Aquaculture Division is responsible for the regulation of the Aquaculture industry in South Australia. The Aquaculture (Zones–Lower Eyre Peninsula) Policy 2013 and Aquaculture (Zones–Tumby Bay) Policy 2015 limits the maximum biomass of sea cage aquaculture animals that can be grown in the zoned areas and is based on a carrying capacity model to determine the suitable amount of fish for each particular region without causing adverse environmental impacts (Department of Primary Industries and Regions - PIRSA).
When assessing an individual licence application there is also 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. 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, including all finfish/tuna sites located within the biounit. Data collected is used to adaptively manage the aquaculture industry in South Australia.
Historically, a Finfish and Tuna Environmental Monitoring Program (FEMP and TEMP respectively) was conducted by the South Australian Research and Development Institute (SARDI). This program involved annual sampling sediment adjacent to actively farmed sites and using DNA profiling to measure changes in the benthic community compared to established control sites between 2005-2013. A temporal and spatial analysis of these data demonstrated no significant difference between farmed sites and control sites within the biounit (Tanner et al 2017).
The EMPs for all sectors were reviewed during the development of the Aquaculture Regulations 2016 to further enhance these programs. As a result, in 2015, a regional based EMP was introduced to the lower Spencer Gulf to monitor the impacts of all aquaculture activity.
This regional program took place over a 4-year period with monitoring undertaken by SARDI. This monitoring program focussed on water quality and infauna, with results used to inform future management arrangements for these two sectors. The final report of the inaugural 4-year program can be found at SARDI Report (pir.sa.gov.au).
In 2019, the second 4-year regional EMP commenced, with a specific focus on seagrass condition and water quality.
SARDI have also completed a report titled 'Carrying Capacity of Spencer Gulf: Hydrodynamic and Biogeochemical Measurement, Modelling and Performance Monitoring', which was released in 2015. This investigated the transport and fate of nutrients within this region which can be used by PIRSA to manage the location and management of sea cage aquaculture throughout the Spencer Gulf.
The modelling described above, along with data from the regional EMP’s, has contributed to the review of the Aquaculture (Zones–Lower Eyre Peninsula) Policy 2013, which commenced in 2019.
The latest modelling demonstrates nutrient outputs are under ANZECC water quality trigger values and generally reach background levels outside of the aquaculture zones, however annual monitoring continues to ensure any impacts are detected.
Integrated Multi-Trophic Aquaculture (IMTA) has been included in the zone policy review which could have the potential to reduce the overall nutrient load discharged within this biounit. In recent years, a new aquaculture sector (macroalgae/seaweed) has emerged within the biounit which will also have positive effects by reducing nutrient levels from anthropogenic sources such as agricultural run-off from Tod river, waste water treatment plan and adjacent aquaculture.
Cleanseas farmed yellowtail kingfish are fed to appetite, ensuring no feed is allowed to fall through the pens without being consumed. Nutrient excreted in the form of faeces is minimised via continual diet improvement. Clean Seas undertakes detailed environmental monitoring programs in both the Louth Bay and Boston Bay regions, with sites specifically selected to compliment the dataset collected by the EPA.
Maximum annual stocking of yellowtail kingfish in the Jussieu region has remained relatively consistent averaging 2568t (range: 2428 – 2755t) between 2016 and 2022. This peak however is short lived and average annual stocking in the Jussieu region was lower at an average of 2182t (range: 1870 – 2531t) between 2016 and 2022.
Tod River transports agricultural runoff with elevated nutrient and sediment loads into nearshore marine waters of Louth Bay
The EP Landscape Board administers the region’s Water Affecting Activity permitting program, which promotes best practice catchment management through the permitting process and ensure a minimum standard in relation to water affecting activities such as dam or watercourse crossing construction, draining or discharging water into a watercourse or excavations in a watercourse.
The Eyre Peninsula Landscape Board is working with landmanagers to fence off and restore riparian and coastal habitats increasing buffering capacity; and manage stock grazing pressure in riparian zones.
The EP Landscape Board have also been focusing on land care actions to help protect and improve temperate saltmarsh along these coastlines. Activities such as monitoring, revegetation, weed management, improving hydrological flows and removing marine debris are contributing to improving these threatened communities.
Jones, A.R., Alleway, H.K., McAfee, D., Reis-Santos, P., Theuerkauf, S.J. and Jones, R.C. (2022). Climate-Friendly Seafood: The Potential for Emissions Reduction and Carbon Capture in Marine Aquaculture. BioScience, 72(2), pp.123–143.
Barrett, L.T., Theuerkauf, S.J., Rose, J.M., Alleway, H.K., Bricker, S.B., Parker, M., Petrolia, D.R. and Jones, R.C. (2022). Sustainable growth of non-fed aquaculture can generate valuable ecosystem benefits. Ecosystem Services, 53, p.101396.
Tanner, J.E., Giblot-Ducray, D. and Loo, M.GK. (2017). Temporal Analysis of Infaunal DNA Data fiom the Tuna and Finfish Environmental Monitoring Programs, 2005-2014. Report prepared for PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2016/000392-1 SARDI Research Report Series No. 916. 24pp.
Observed Condition
Expected Condition