Last updated: 5 March 2026.
Since the middle of March 2025, South Australian coasts have been afflicted by a toxic algal bloom of unprecedented size and duration. The effects of the bloom on marine life have been devastating, with untold thousands of dead creatures, from tiny worms to large sharks, washing up on the beaches from Encounter Bay and Kangaroo Island to shores on both sides of Gulf St Vincent. Underwater surveys indicate that mortalities seen on the beaches are only a small fraction of what is happening off-shore.
Initially, one of the dominant organisms originally identified in the bloom was a dinoflagellate, Karenia mikimotoi. It is highly cytotoxic, although the precise mechanism of its primary toxic action is still not fully understood. In November, 2025, another species, Karenia cristata, was identified as a dominant species in many samples of the bloom. It is a significant producer of brevetoxin, which has well-described neurotoxic and respiratory actions. Other species of dinoflagellates detected to varying degrees in the bloom include Karenia papilionacea which also produces brevetoxin, Karenia brevisulcata, which produces a brevetoxin-like toxin and a cytotoxin, and Karlodinium species which produce a range of karlotoxins, which are well understood cytotoxins.
As the bloom has progressed, various citizen science groups, independent researchers, university researchers and government departments have been working to monitor and understand the genesis, progression and effects of the toxic algal bloom. As a result of my background in zoology, comparative anatomy and physiology, and both cellular and systems neuroscience, it turns out that I am one of the few people around who has significant background knowledge of how the various algal toxins affect different cell types and organ systems is a wide range of marine creatures. Consequently, I have contributed directly to several citizen science projects and have spoken about the toxins at public forums.
Other than the fact that they existed, I knew almost nothing about dinoflagellates before this bloom event. I experienced some of their toxic effects after windsurfing in Encounter Bay on the weekend of the bloom’s first significant appearance along that coast. Since then, I have learned a huge amount from independent scientists, Janine Baker, Faith and Peri Coleman, amongst many other experts who have been willing to share their time and knowledge.
New information and new interpretations of exisiting data are appearing all the time. Consequently, I am updating this site regularly in order to present the latest and most accurate information. The most recent update is indicated at the top of this page.
Unless specified otherwise, all illustrations and photographs are by me. Most technical terms are hyperlinked to the relevant pages in Wikipedia or other on-line resources that I have checked for accuracy. The scientific literature underpinning this article is large and diverse: key papers are cited via footnotes. The full list of citations can be seen on the References page. Where possible, the selected publications are open access.
Click on the headings or images in the topic list below to go the relevant section.
For key information on the bloom, the organisms in it, its effects, and how it is being monitored, visit these sites:
The Great Southern Reef Foundation
These comprehensive updates by Janine Baker are the most complete overviews of the effects of the bloom on the marine ecosystems, using data from citizen science and government sources.
https://greatsouthernreef.com/2025-algal-bloom-june-update
https://greatsouthernreef.com/2025-sa-algal-bloom-spring-update
The Government of South Australia Algal Bloom portal
https://www.algalbloom.sa.gov.au
SA Government water testing results for the algal bloom are here:
https://experience.arcgis.com/experience/5f0d6b22301a47bf91d198cabb030670
Luke Mosley has created an excellent app that integrates water testing results from the SA Government site and from citizen scientists:
https://sa-algal-bloom.streamlit.app
The SA Marine Mortality Events 2025-2026 community on iNaturalist
https://www.inaturalist.org/projects/sa-marine-mortality-events-2025-2026
The ANZ Marine HAB Network has been established to facilitate information gathering and sharing on marine harmful algal blooms
https://www.anzhabnet.com
If you experience health symptoms following exposure to the bloom, you can report them via the Bloomin’ Algae citizen science reporting portal. The information you provide is anonymous and will be used to help create a database that can be analysed at a later date.
https://www.bloominalgae.com.au/health-incident-reporting
Here are some of the core textbooks I have used as source material. They are mostly in print and available from large booksellers.
The only comprehensive, up-to-date resource on phytoplankton relevant to the bloom is Harmful Australian Marine Microalgae by Gustaaf M Hallegraeff (CSIRO Publishing, 2024):
https://www.publish.csiro.au/book/8143
For an excellent overview of plankton in general, with a strong Australian focus, see Plankton: A Guide to their Ecology and Monitoring for Water Quality, 2nd Edition, edited by Iain M Suthers, David Rissik & Anthony J Richardson (CSIRO Publishing, 2019): https://www.publish.csiro.au/book/7808
For the most comprehensive overview of the biology, evolution and development of marine invertebrates affected by the bloom (as well as all other types of invertebrates!) see Invertebrates, 4th Edition, by Richard C Brusca, Gonzalo Giribet & Wendy Moore (Sinauer / Oxford, 2023). https://www.oup.com.au/books/higher-education/science/9780197554418-invertebrates
For an excellent overview and detailed descriptions of how animals interact at cellular and systems levels with their environments, see Animal Physiology: An Environmental Perspective by Patrick J Butler, J Anne Brown, D George Stephenson & John R Speakman (Oxford University Press, 2021) https://www.oup.com.au/books/higher-education/science/9780199655458-animal-physiology
For detailed but accessible information on the how fish breathe, swim, and otherwise interact functionally with their environments, see The Physiology of Fishes, 5th edition, edited by Suzanne Currie & David H Evans (CRC Press, 2021) https://www.routledge.com/The-Physiology-of-Fishes/Currie-Evans/p/book/9780367477554
For just about everything you’d ever want to know about sharks and rays, see The Biology of Sharks and Rays by A Peter Klimley (University of Chicago Press, 2013) https://press.uchicago.edu/ucp/books/book/chicago/B/bo11018459.html
For identifying South Australian marine invertebrates, my first look-up is A Field Guide to the Marine Invertebrates of South Australia by Karen Gowlett-Holmes (notomares, 2008) ISBN 9780980485400. Then Field Guide to the Seashores of South-Eastern Australia by Christine Porter, Ty G Matthews, Alecia Bellgrove & Geoff Wescott (CSIRO Publishing, 2023) https://www.publishing.csiro.au/book/8030
For identifying and information about South Australian fish, I have started with three fine books, unfortunately all now out of print: The Marine and Freshwater Fishes of South Australia by TD Scott, CJM Glover & RV Southcott (SA Government Printer, 1974); A Field Guide to the Common Sea & Estuary Fishes of Non-Tropical Australia by JM Thomson (Collins, 1977); and Australian Seafood Handbook – Domestic Species edited by GK Yearsley, PR Last & RD Ward (CSIRO Marine Research, 1999). Further valuable information came from Swainston’s Fishes of Australia by Roger Swainston (Viking, 2010) https://animafish.com/products/swainstons-fishes-of-australia.
In addition to these (and other) books, species can be identified by many on-line resources, most notably, the Atlas of Living Australia: https://ala.org.au.
Introduction to toxins in the South Australian bloom
The effect of cytotoxins on gill function
Why are so many dead juvenile leatherjackets washed up?
What might be causing the skin flushing in sharks and rays?
Effects of the toxins on humans
Effects of the toxins on other creatures
Defences of fish against the bloom
A consolidated list of all the references used in these articles.
“they used to place coins on the eyelids of the dead so they could not follow the lives of the living … surrounded by ocean we find no clear water … in the absence of fire our soft tissues are burning … yet our eyes stay open …”
This is my video about the bloom, from the point of view of the fish that have been affected by it… For an extended account of what went in making this video, please see https://liberatedwords.com/2026/02/13/deadeye-a-poetry-video-response-to-an-environmental-catastrophe-ian-gibbins-january-2026/
If you find an error or something that needs a more clear explanation, please send me a message via the form below. Thank you.
