Executive Summary
Historical records confirm repeated coastal observations of water discolouration, fish mortality, and harmful algal events in South Australia over more than a century.
“Discoloured water caused by plankton blooms has been recorded periodically in South Australian coastal waters since the early twentieth century.” [A]
Documented events show consistent environmental drivers including nutrient availability, water temperature, and water column stability. The record also includes specific fin-fish mortality events in both tuna and kingfish aquaculture.
These records support that the events are recurring system responses, not isolated incidents.
1 Forward Timeline (Source Anchored)
1800s
“An extensive growth of confervoid vegetation coloured the waters of Lake Alexandrina green.” [B]
“The water assumed a green colour and emitted an offensive odour.” [C]
Early 1900s
“Discoloured water caused by plankton blooms has been recorded periodically in South Australian coastal waters since the early twentieth century.” [A]
1956–1959 (Murray Flood Period)
“Muddy water extended far out to sea from the Murray Mouth following flood discharge.” [D]
“Large volumes of freshwater entered the coastal zone, significantly altering salinity conditions.” [E]
“Fish kills were reported in the lower river and estuarine regions during and after the flood.” [F]
“Floodwaters carried heavy loads of silt and organic matter into coastal waters.” [G]
1987
“In 1987 a bloom of Alexandrium catenella in Gulf St Vincent caused paralytic shellfish poisoning and led to the closure of shellfish harvesting areas.” [H]
1996
“Mass mortality of captive southern bluefin tuna occurred in Boston Bay, South Australia, in April–May 1996.” [I]
“The event represented a complex diagnostic problem involving several environmental factors.” [J]