Chapter 1Introduction

Referral of the inquiry

1.1On 23 July 2025, the Senate referred an inquiry into the algal blooms in South Australia (the inquiry) to the Senate Environment and Communications References Committee (the committee) for inquiry and report by 28 October 2025, with the following terms of reference:

The causes, frequency, scale and duration of recent algal blooms in South Australian marine and coastal environments, with particular reference to:

(a)contributing environmental, land management or water quality factors;

(b)ecological, economic, cultural and social impacts of algal blooms with particular reference to:

(i)tourism, commercial and recreational fishing industries,

(ii)regional and coastal communities, and

(iii)marine biodiversity and ecosystem health;

(c)the cultural and economic impacts on Indigenous communities, including any loss of access to traditional fishing;

(d)the coordination of state and federal government responses, including support, industry engagement and scientific advice;

(e)the current support and recovery arrangements for impacted industries and communities, including:

(i)financial support for fishing, tourism and other impacted businesses,

(ii)community resilience services, and

(iii)research, monitoring and restoration efforts;

(f)the adequacy of long-term monitoring, forecasting and prevention strategies, including funding and institutional support for marine science and environmental data collection; and

(g)any related matters.[1]

1.2The committee was granted extensions of time to report to 4 November 2025[2] and 11 November 2025.[3]

Conduct of the inquiry

1.3Details of the inquiry were advertised on the committee’s website, including a call for submissions by 22 August 2025. The committee wrote directly to various stakeholders to invite them to make submissions.

1.4The committee received 155 submissions, which are listed at Appendix 1 and are available on the committee’s website.

Public hearings

1.5The committee held five public hearings, including four public hearings in South Australia (SA), in:

Seacliff, Adelaide on 9 September 2025;

Port Lincoln, Eyre Peninsula on 10 September 2025;

Ardrossan, Yorke Peninsula on 11 September 2025; and

Victor Harbor, Fleurieu Peninsula on 12 September 2025.

1.6A fifth public hearing was held in Canberra on 24 September 2025.

1.7A list of witnesses who attended the public hearings is available at Appendix 2. Hearing programs, transcripts of hearings, and answers to questions on notice are available on the committee’s website.

Site visits

1.8The committee also undertook two site visits while in SA.

1.9The committee first conducted a site visit to the Seacliff beachfront on 9 September 2025 to view areas affected by the algal bloom (see Figures 1.1 and 1.2). The walk, guided by Professor Michael (Mike) Steer, Executive Director of the South Australian Research and Development Institute (SARDI), and Mr Chris Beattie, Coordinator of the Algal Bloom Response in the SA Department of Premier and Cabinet, provided committee members with an opportunity to observe first-hand the impacts of the algal bloom on the local environment and community.

Source: Secretariat

1.10The committee extends it appreciation to Ms Charmaine Hughes, Mr Brian Abbott, Mr Josh Ross and Mr Troy Burgess, members of the beach clean up crew, for taking the time to talk to committee members about the work being undertaken to clear marine animals and plant matter from the beaches each day.

Source: Secretariat

1.11The committee also conducted a site visit in Port Lincoln on 10 September 2025 to gain an understanding of the impacts of the algal bloom on local marine industries, and spoke directly with representatives of the mussel industry (see figure 1.3).

1.12The committee thanks Ms Emily Rowe, Director of Seafood Industry SA for assisting with arrangements for the visit and Mr Mark Andrews, General Manager of Mussel Operations at Yumbah Aquaculture. The committee also thanks representatives of the SA Government who attended, including Dr Andrew Dunbar, Executive Director of the Department of State Development, and Professor Gavin Begg, Executive Director of Fisheries and Aquaculture at the South Australian Department of Primary Industries and Regions (PIRSA).

Source: Secretariat

Acknowledgements

1.13The committee thanks the organisations and individuals who made submissions, and attended public hearings, for their time and contributions to this inquiry.

Structure of the report

1.14This report comprises seven chapters:

Chapter 1 provides details of the inquiry and background information on the harmful algal bloom in SA, including a brief outline of a similar algal bloom that occurred in SA in 2014;

Chapter 2 outlines the key contributing factors for the bloom, and discusses current and future management strategies, forecasting and prevention strategies, and the international experience of Karenia mikimotoi blooms;

Chapter 3 outlines the role of the SA and Commonwealth Governments in the response to the harmful algal bloom, including support and recovery arrangements, and discusses the application of the emergency declaration framework;

Chapter 4 sets out evidence relating to the ecological, economic and social impacts of the algal bloom on marine biodiversity and ecosystem health;

Chapter 5 continues to discuss the ecological, economic and social impacts of the algal bloom on industries which rely on ocean health, and on regional and coastal communities;

Chapter 6 sets out the human health impacts of the algal bloom;

Chapter 7 sets out the cultural and economic impacts on First Nations communities; and

Chapter 8 sets out the committee view and recommendations.

Background information on the 2025 harmful algal bloom (HAB)

Algal blooms in coastal waters

1.15Algal blooms are a natural occurrence in coastal waters globally, and can be caused by multiple factors including extended hot periods, low winds and low tidal ranges.[4] Predicting algal blooms can be difficult, and the severity of the bloom can vary depending on factors such as marine heatwaves (MWHs) and nutrient pollution.

1.16In certain circumstances, including the spread of the 2025 algal bloom impacting SA coastal waters, algal blooms can negatively impact the local ecosystem in which they are occurring. In these cases, the bloom is referred to as a harmful algal bloom (HAB).[5]

1.17The species of algae that makes up the bloom can also affect its severity, as there are some species of algae that are toxic to marine life, whereas some other species of algae will cause harm to fish by removing oxygen from the water.

1.18The Australian and New Zealand Marine Harmful Algal Bloom Network (ANZMHAB Network) highlighted that, according to the Intergovernmental Oceanographic Commission of UNESCO Harmful Algal Event Database, there have been 124 HABs in Australia between 1770 and 2025.[6]

1.19HABs affect the marine ecosystem in a number of ways. Depending on the species of algae that make up a HAB, they can affect marine life in a variety of negative ways, even in low concentrations. This includes causing gill damage directly to marine life, creating toxins, and reducing the amount of oxygen available in the water to levels below what is required to sustain marine life.[7]

1.20HABs can have human health impacts, which can be caused by exposure to the water affecting breathing and the eyes or consumption of seafood that has accumulated toxins created by the HAB.[8] Further information surrounding the impact of HABs on human health is discussed in Chapter 6 of this report.

South Australian harmful algal bloom

1.21SA is currently experiencing ‘one of the largest scale, naturally occurring algal bloom events ever recorded in Australian waters’.[9]

1.22The specific species that comprises the HAB currently occurring in SA was initially stated to be Karenia mikimotoi (K. mikimotoi), a phytoplankton that has been responsible for multiple and frequently-occuring HABs globally, resulting in large fish kills. The ANZMHAB Network provided information on the Kareniaceae family:

The family Kareniaceae is a group of microalgal species belonging to the Dinophyceae (dinoflagellates). HABs involving Kareniaceae are well known for their fish-killing (ichthyotoxic) effects and some species have substantial human health impact due to the production of toxins, including neurotoxins (nerve-toxins) called brevetoxins. Many species of Karenia look very similar under high-powered microscopes and can be very difficult to distinguish from one another. Even for experts, identification can difficult using morphology alone.[10]

1.23More recent information has shown that the HAB is likely made up of multiple Karenia species including K. mikimotoi.[11] SARDI stated that the current HAB is likely to be a number of species within the Karenia family, some of which produce brevetoxins (marine neurotoxins):

Our level of understanding of the algae is that it's a complex composition of species within the Karenia family. We've heard about Karenia mikimotoi—I mentioned it early on—but there are likely a number of other species, and they have various means of producing brevetoxin-like substances. So there's clearly a relationship between the algal bloom and the production of brevetoxins.[12]

1.24Other evidence to the inquiry has claimed that there may also be an unknown species making up the HAB, and that it may be years before the exact species in the current HAB are known.[13] The ANZMHAB Network, for example, stated that there are several undescribed species of Karenia which occur in Australian waters, and whose toxicity is not known.[14]

1.25The HAB has affected more than 30 per cent of the SA coastline, and with more than 13,000 recorded animal deaths as well as other impacts, which are discussed throughout this report.[15]

1.26Commonwealth Department of Climate Change, Energy, the Environment and Water (DCCEEW) noted that recorded observations reference the deaths of tens of thousands of marine animals from more than 480 species, with the full extent of the impact unlikely to be known for some time.[16] The SA Government acknowledged that observed mortalities will be ‘only a small proportion of the total mortalities that continue to result’ from the bloom:

This is particularly important given approximately 85% of fish species, 95% of molluscs and 90% of echinoderms are endemic to the Southern temperate coast of Australia while the temperate macroalgal flora has a richness 50-80% greater than other comparable regions around the world.[17]

1.27The duration of the HAB is difficult to predict. The SA Government stated that a range of factors can determine the dissipation of a bloom:

Based on our observations, research and international expertise, it is difficult to predict the duration and spread of algal blooms. Factors that can lead to the decline or end of the bloom include a change in environmental conditions such as cooler temperatures, increased mixing and water flow, decreased sunlight, and decreased nutrient availability. This is a dynamic situation as the bloom travels depending on weather and water conditions and the impact on people in these areas can therefore be unpredictable.[18]

Affected areas

1.28The HAB has affected an expansive geographic area, with elevated levels of chlorophyll-a, an indicator of the presence of algae, being identified in high concentrations in both the Spencer Gulf and Gulf St Vincent, the north coast of Kangaroo Island, and along the coast south-east of the Fleurieu Peninsula, with elevated levels being identified as far away as Beachport, which is approximately 380 km south-east of Adelaide.[19]

1.29SA coastal waters affected by the HAB (at time of writing) include the below, and pictured at Figure 1.1 below:

Adelaide’s metropolitan beaches

Port River and West Lakes

Southern Fleurieu Peninsula

Kangaroo Island

The Coorong

Yorke Peninsula

Gulf St Vincent

Eyre Peninsula

Spencer Gulf. [20]

Figure 1.1: Satellite imagery of chlorophyll-a, which provides an indication of algae concentrations as of 12 October 2025

15 September 2025 - Satellite imagery of chlorophyll-a, which provides an indicator of algae concentrations but not necessarily concentrations of harmful algae, is being used to monitor the algal bloom. Areas in red have higher levels of chlorophyll-a.

Source: Government of South Australia, Algal Bloom Update: Affected Areas, 15 September 2025, https://www.algalbloom.sa.gov.au/where-the-algal-bloom-is, accessed 22 September 2025.

1.30The current HAB outbreak of K. mikimotoi was identified in the waters around the Fleurieu Peninsula, near Waitpinga and Parsons Beach. The SA Government stated in an update on 27 August 2025 that:

Daily satellite measures of chlorophyll-a (chla) levels, an indicator of algae concentrations, show elevated chla concentrations persist around the coastline of Gulf Saint Vincent north of Edithburgh in the west and extending south in a narrow band along the coast along the eastern side of the gulf to the southern tip of the Fleurieu Peninsula. Patches of elevated chla are observed near Goolwa, Penneshaw on Kangaroo Island and Kingston in the southeast. Regions of high chla concentrations in Spencer Gulf include along the western coastline from Port Lincoln to Munyaroo and around Hardwicke Bay and Moonta in the east.[21]

Water testing results

1.31K. mikimotoi grows outside of HAB conditions, with average levels of the alga being <5000 cells/L. This species was also responsible for the Coffin Bay HAB that occurred in February of 2014.[22]

1.32Water testing undertaken between 21 and 26 August 2025 showed levels of the Karenia species of alga:

Source: SA Government, South Australian Harmful Algal Bloom - Water Sampling Dashboard (accessed 1 September 2025).

1.33Water testing undertaken between 18 September and 13 October 2025 showed levels of the alga:

Source: SA Government, South Australian Harmful Algal Bloom - Water Sampling Dashboard (accessed 17 October 2025).

Identified causes

1.34The SA Government has identified three potential contributing factors to the HAB, which was first detected in March 2025:

an MHW which started in September 2024 and saw sea temperatures about 2.5°C warmer than usual, combined with calm conditions, light winds and small swells;

the 2022-23 River Murray flood, which washed extra nutrients into the sea; and

a cold-water upwelling in summer 2023-24 that brought nutrient-rich water to the surface.[24]

1.35The Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the DCCEEW identified an additional contributing factor to the HAB based on information from the SA Government, being anomalous weak winds in the summer of 2025. The weaker winds reduced the dilution of the algae, keeping it in optimal conditions for growth.[25]

1.36Further information on the contributing factors to the HAB is discussed in Chapter 2 of this report.

2014 Coffin Bay harmful algal bloom

1.37A significant, but comparatively small HAB occurred in 2014, in Coffin Bay, in SA. The 2014 Coffin Bay HAB was contained entirely within Coffin Bay, with minimal impact to surrounding areas, compared to the 2025 HAB occurring across a large portion of the water off the coasts near Adelaide due to its origin point giving it greater access to the gulfs near Adelaide.[26]

1.38In February 2014, a commercial diver reported abalone mortalities at Frenchman’s Bluff in the outer part of Coffin Bay (which is located on the Eyre Peninsula west of Adelaide), to the PIRSA in line with PIRSA’s abalone viral ganglioneuritis disease response plan. Following this, PIRSA conducted dive surveys along the coast to the north and south of the reported mortality site. Divers observed that the mortalities were localised at Frenchman’s Bluff and appeared to be due to an algal bloom. The SA Shellfish Quality Assurance Program (SASQAP)[27] analyses of water samples confirmed high density (12 million cells/L) of K. mikimotoi.[28]

1.39Following this, PIRSA’s incident management team met, and an emergency management structure was developed for the investigation and coordination. Teams were assembled to survey the beaches and waters in Coffin Bay, with updates provided to the Minister, state government departments, and seafood industry stakeholders. PIRSA confirmed that the likely cause of the mortality event was K. mikimotoi.[29]

1.40PIRSA continued to monitor the situation, conducting surveys and collecting water samples to measure K. mikimotoi counts in the affected area. It was noted that only a small number of marine organisms had washed ashore. In March 2014, dive surveys identified no further mortalities at any of the previously identified sites despite high concentrations of algae.[30]

1.41By 4 March 2014, PIRSA assessed that the severity of the HAB had significantly reduced, no new mortalities had been identified, and that the concentration of K. mikimotoi had greatly reduced. The led to a passive surveillance phase in line with the PIRSA Aquatic Animal Health Plan.

Next chapter

1.42The next chapter outlines the potential contributing factors to the HAB, and discusses long-term monitoring, forecasting and prevention strategies and possible approaches to lessen the impact of future blooms.

Footnotes

[1]Journals of the Senate, No. 2, 23 July 2025, p. 72.

[2]Journals of the Senate, No. 17, 28 October 2025, p. 569.

[3]Journals of the Senate, No. 21, 4 November 2025, p. 670.

[4]Algal blooms in coastal waters differ from those in freshwater in a number of ways, including biology, diversity, toxins, drivers and impacts. Australian and New Zealand Marine Harmful Algal Bloom Network (ANZMHAB Network), Submission 73, p. 2. Further details on the contributing factors of the HAB are outlined in Chapter 2 of this report.

[5]Environment Protection Agency, Government of South Australia (SA EPA), Harmful algal blooms (HABs) and marine heat waves, 27 May 2025 (accessed 24 July 2025).

[6]ANZMHAB Network, Submission 73, p. 2

[7]ANZMHAB Network, Submission 73, p. 3.

[8]ANZMHAB Network, Submission 73, p. 3.

[9]South Australian (SA) Government, Submission 71, p. 1.

[10]ANZMHAB Network, Submission 73, p. 4. Emphasis in original.

[11]See, for example, Professor Michael (Mike) Steer, Executive Director, South Australian Research and Development Institute (SARDI), Proof Committee Hansard, 9 September 2025, p. 13; Ms Faith Coleman, Submission 33, p. 1; Biodiversity Council, Submission 66, p. 4; Professor Shauna Murray, Submission 72, [p. 2].The presence of multiple algae species is discussed in the next chapter.

[12]Professor Steer, SARDI, Proof Committee Hansard, 9 September 2025, p. 13.

[13]Dr Christopher Bolch, private capacity, Proof Committee Hansard, 24 September 2025, p. 14.

[14]ANZMHAB Network, Submission 73, p. 4

[15]Mr Chris Beattie, Coordinator, Algal Bloom Response Coordination Unit, Department of the Premier and Cabinet, Proof Committee Hansard, 9 September 2025, p. 12.

[16]Department of Climate Change, Energy, the Environment and Water (DCCEEW), Submission 67, p. 13.

[17]SA Government, Submission 71, p. 4.

[18]SA Government, Submission 71, p. 1

[19]South Australian Department of Primary Industries and Regions (PIRSA),Harmful algal bloom (HAB) situation update, (accessed on 29July 2025).

[20]SA Government,Where is the algal bloom (accessed 16 September 2025).

[21]SA Government, South Australian Algal Bloom Situation Update: 27-08-25 (accessed 1 September 2025).

[22]Shane Roberts, Clinton Wilkinson, Ben Stobart, Mark Doubell, Paul van Ruth and John Gilliland, ‘Fish Kill investigation: Coffin Bay harmful algal bloom February 2014’, March 2014, p. 7 (accessed 24 July 2025).

[23]K. mikimotoi was not detected.

[24]SA Government, Learn about the algal bloom (accessed 12 August 2025).

[25]Commonwealth Scientific and Industrial Research Organisation (CSIRO), Submission 31, p. 5; and DCCEEW, Submission 67, p. 3.

[26]Dr Mark Doubell, Research Scientist, Oceanography Subprogram Leader, SARDI, Proof Committee Hansard, 9 September 2025, p. 18.

[27]The SA Shellfish Quality Assurance Program (SASQAP) is a joint initiative between PIRSA and the shellfish industries of SA and regularly monitors all accredited shellfish harvesting areas in SA for toxic algae and provides guidance for producers.

[28]Shane Roberts, Clinton Wilkinson, Ben Stobart, Mark Doubell, Paul van Ruth and John Gilliland, ‘Fish Kill investigation: Coffin Bay harmful algal bloom February 2014’, March 2014, p. 9 (accessed 24 July 2025).

[29]Shane Roberts, Clinton Wilkinson, Ben Stobart, Mark Doubell, Paul van Ruth and John Gilliland, ‘Fish Kill investigation: Coffin Bay harmful algal bloom February 2014’, March 2014, pp. 9–10 (accessed 24 July 2025).

[30]Shane Roberts, Clinton Wilkinson, Ben Stobart, Mark Doubell, Paul van Ruth and John Gilliland, ‘Fish Kill investigation: Coffin Bay harmful algal bloom February 2014’ March 2014, p. 9 (accessed 24 July 2025).