Old and cold To collect the crystalline crusts, divers chiseled off calcite shards from underwater rocks in the Labrador Sea offshore of Kingitok Island and in the Arctic Ocean near Nunavut, Canada.
The oldest algae crusts contained 646 years of layers, confirmed by carbon dating, the researchers said. The algae, called Clathromorphum compactum, owes its long lifespan to its thick calcite crust and a different protective layer, called eitihallium, that keeps grazing animals from chomping too much of the algal surface, Halfar said.
While 646 years won't put the algae near the record for the world's oldest plant (which is held by trees such as 5,000-year-old bristlecone pines), the discovery does add to the list of long-lived, cold-loving species. Sponges in Antarctica may live for up to 10,000 years, and mollusks collected offshore of Iceland can live for more than 500 years.
The algae's lifespan is theoretically unlimited, Halfar said. "Much longer records are possible, and in fact, during an expedition this past summer, our group sampled some specimens off Labrador that, based on their thickness are well over 1,000 years old (in-depth analysis and dating pending)," Halfar told LiveScience.