Microscope view of hard coral polyps showing zooxanthellae

A young hard coral with polyps. The small brown flecks inside the coral are single-celled algae called zooxantellae.

This image is of a 12 week old Acropora Tenuis recruit grown in the AIMS National Sea Simulator, taken with a dissecting microscope. The recruits were grown on tiles and transported to the microscope in a box of water.