Record El Niño Risks Seaweed Takeover of Great Barrier Reef — SkimNews
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- David Schoeman at the University of the Sunshine Coast warns the Great Barrier Reef could cross a tipping point into an algal-dominated ecosystem, a flip he says is easy to enter but very hard to reverse even if temperatures later normalize.
- Neal Cantin at AIMS reports that 2024 saw severe bleaching across the entire reef — affecting 60% of corals across roughly 40% of the reef, with 70–90% coral mortality in many zones — compared with just 8% mortality in 1998 and 35% in 2016.
- Cantin says the current El Niño is "record-breaking" and won't peak until November, and the bleaching footprint has expanded to offshore systems like Swains Reefs (150 km offshore) that were once buffered by deep cool water — a buffer that broke down in 2024.
- Schoeman documents six bleaching events in the past decade, with mass bleaching now striking even in La Niña years because baseline ocean warming is stacking on top of El Niño heat stress.
- Daniel Harrison at Southern Cross University is leading marine cloud brightening research — spraying seawater to brighten clouds and reflect sunlight — but field trials are unlikely before 2028, leaving the reef without that mitigation tool this summer.
- Harrison's team found that an 80% reduction in sulphate aerosols from shipping in the reef region adds an extra 0.15°C of sea-surface heating, a hidden consequence of cleaner-air policies that is compounding coral heat stress.
Why it matters: The reef is approaching an irreversible regime shift: 70–90% mortality in many zones in 2024 and six bleaching events in a decade show recovery windows are collapsing, while the most promising near-term intervention (marine cloud brightening) won't reach trials until at least 2028 — meaning the reef faces this record El Niño peak in November with no deployable geoengineering backstop and only decarbonization as a long-term lever.
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