WFS Admin

The Great Southern Reef Research Partnership (GSRRP) warned in 2023 that a bloom was likely, mainly because of a worsening marine heatwave.

Late 2024 – The Setup

October–December 2024

Sea-surface temperatures in the Great Australian Bight and South Australian gulfs start trending 1–2°C above average due to a combination of El Nino conditions and climate change–driven ocean warming.

Satellite observations pick up weaker-than-normal winter mixing in gulf waters, meaning nutrients and oxygen are not being redistributed effectively.

Scientists begin noting ideal preconditions for a summer marine heatwave, similar to those described in the 2023 warning from the Great Southern Reef Research Partnership (GSRRP).

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Early 2025 – Conditions Intensify

January–March 2025

Marine heatwave thresholds are breached in parts of Spencer Gulf and Gulf St Vincent — water temps stay above the 90th percentile for multiple weeks.

Local marine biologists report that early microalgae density increases.

Commercial fishers notice patchy fish movements, likely due to lower oxygen in warmer waters.

No emergency intervention triggered — conditions monitored but not acted upon, though what could be done is debatable.

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Mid 2025 – Scientists Renew Warnings

May 2025

GSRRP sends a second formal warning to the federal government, highlighting that sea temperatures were now persistently in the danger zone.

Reports nutrient levels consistent with bloom development, partly from agricultural runoff and partly from a natural upwelling.

Warns explicitly that a toxic algal bloom in the gulfs is “highly probable” in the coming months.

Urges rapid-response measures — such as coordinated water sampling, aquaculture monitoring, and contingency plans for closures.

Federal government does not allocate emergency funding at this stage.

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The Bloom Survives Winter

July 2025

Bloom expands rapidly across Spencer Gulf and into Gulf St Vincent.

Fish kills reported along the Eyre Peninsula and Yorke Peninsula.

Mussel and oyster farms suspend harvesting in affected areas due to paralytic shellfish toxin (PST) levels.

Federal government announces $14 million emergency package — most funds aimed at research and industry relief.

Scientists state bloom is well established and cannot be reversed in the short term.

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August 2025

Bloom continues to affect large areas. Fishery closures in place.

Economic impacts estimated in the tens of millions for SA’s seafood industry.

Calls from scientists and industry leaders to establish the national reef monitoring program first requested in 2023.

State and federal agencies collaborating on post-bloom recovery plans, but the bloom may continue as the water warms again into spring and summer.