Every winter, a sliver of the South Australian coast becomes the world's hottest spot for giant cuttlefish romance. Hundreds of thousands of these shape-shifting, color-shifting cephalopods show up for a mating frenzy so epic it draws divers from around the globe. But this year, the party was a dud: official figures released this month estimate just 1,811 cuttlefish turned up to mate, down from 63,000 last year - a 97% drop that has sparked fears of a 'catastrophic decline'.

The state government points a finger at a toxic algal bloom that has been ravaging the coastline for over 18 months. The bloom, caused by ocean warming, marine heatwaves, and nutrient pollution - all exacerbated by climate change - has been particularly rough on cuttlefish, octopus, and squid. And the numbers are grim: only 440 eggs were counted this season, instead of the millions usually laid.

Manny Katz, 28, was one of four divers tasked by South Australia's Department of Environment and Water to assess the damage. Over two days in July, his team did eight one-hour dives, scouring under rocks along eight kilometers of coast. 'There would normally be millions of eggs,' he said. Instead, they found about 440. Adult cuttlefish live only 12 to 18 months, so this breeding season's success determines next year's population. 'We don't know if the population is ever going to be able to recover,' Katz lamented.

The few adults they did see were acting skittish, hiding under rocks - no strength in numbers. Katz wasn't shocked, given the algal bloom's devastation since March last year. 'This is the canary in the coal mine,' he said. Stefan Andrews, co-founder of the Great Southern Reef Foundation, is pushing to list the giant Australian cuttlefish as threatened, noting the bloom is a 'leading plausible explanation' but not definitively proven.

A spokesperson for South Australia's Department of Primary Industries and Regions noted that cuttlefish populations 'naturally fluctuate' - from a record low of 13,500 in 2013 to a high of 247,000 in 2020. Prof Mike Steer of the South Australian Research and Development Institute called the low estimate 'disheartening' but remained hopeful, as the population rebounded to over 100,000 within two years of the 2013 slump. He pointed to 'positive signs' of continued egg-laying.

So, will the cuttlefish bounce back? Only time - and a lot less toxic algae - will tell. But for now, the Cuttlefish Coast is a lot less crowded, and a lot more concerning.