Along the Ryukyu Islands of southern Japan, a liter of seawater drawn from above a coral reef now carries enough genetic information to name what lives below — a quiet revolution in how humanity listens to the ocean. Researchers at the Okinawa Institute of Science and Technology have built an atlas of 231 reef sites by reading the DNA that corals shed into the water column, mapping both abundance and absence across shallow and deep habitats. The work arrives as the fourth global bleaching event reshapes reefs worldwide, offering science a way to count what is being lost before the counting bec