Giant clam shell reveals 200 years of Great Barrier Reef climate data

Researchers have used the shell of a giant clam (_Tridacna gigas_) to reconstruct month-by-month climate conditions at the Lizard Island Group in the northern Great Barrier Reef from approximately 200 years ago.

As the clam grows, it creates microscopic daily lines and broader annual bands in its shell, similar to tree rings. By analyzing the geochemistry of these layers, scientists can decode how the surrounding seawater changed over the animal's long lifetime. The findings indicate that prior to widespread industrial-era warming, summers at Jiigurru (Lizard Island Group) were cooler than they are today, while winter conditions remained surprisingly similar.