'Dread': coral scientists fear bleaching El Nino could bring

Forecasters predict a potentially powerful El Nino weather system will arrive this year, raising fears of catastrophic coral bleaching worldwide. El Nino, occurring every two to seven years, disrupts weather patterns, warms seawater, and reduces cloud cover—conditions that trigger coral bleaching by forcing algae to leave or be expelled, starving the reefs. Clint Oakley, a coral scientist at Victoria University of Wellington, described the prospect as 'dread, although not surprise,' noting every global bleaching event has coincided with El Nino. Without algae, corals turn white and starve, leaving them vulnerable to disease and unable to reproduce. Jen Matthews, a scientist at the University of Technology Sydney, warned that prolonged heat or extreme temperatures will kill corals entirely. The 2024 global mass bleaching event already devastated reefs, with Australia’s Great Barrier Reef losing 15-40% of its coral cover and some Caribbean species becoming 'functionally extinct.' A strong El Nino would further raise sea temperatures, which are already near the lethal threshold seen in the 1998 bleaching event. Scientists say up to 50% of the world’s coral has been lost in recent decades, threatening ecosystems that support fisheries and coastal protection. While some corals show resilience, experimental techniques like nutritional gels, shading, and genetic engineering are only 'buying time,' according to Matthews. Kimberley Reid, a research fellow at the University of Melbourne, cautioned that El Nino’s strength and duration remain uncertain, but its arrival would exacerbate warming already caused by climate change. Even without El Nino, the long-term outlook for coral reefs remains dire.