This image illustrates how scientist measure a coral for size and growth rate. First, the edges of a structure are identified (a) and then the coral is digitally measured in pixels from the edge of a structure to the tip of the colony (b). The structure of known diameter is measured in pixels and then pixels are converted into centimeters (c). Distance “b” is divided by the number of years the structure has been submerged to get colony growth rate in centimeters per year. Division of coral length by the total number of years a structure is submerged assumes that the coal settled immediately after the structure was put in place. Because the coral may have settled at a later date, growth rate estimates using this method are always minimum growth rates. Image courtesy of Lophelia II 2012 Expedition, NOAA-OER.