How are single-shot photographs orthorectified?: Comment on "Quantifying sponge communities from shallow to mesophotic depths using orthorectified imagery" (Lesser et al. 2023)

For many decades, marine ecologists have used the point-intercept method to estimate the percentage cover of organisms on topographically complex benthic substrata (i.e., hardbottom reefs), whether applied directly in the field or to photographs. A recent Method article in this journal (Lesser et al., Mar Biol, 2023) claimed that this method is flawed when applied to photographs if the images are not orthorectified. This claim is factually incorrect, and the article is fundamentally in error. The article misuses the terms "orthorectification" and "orthorectified" and does not provide a method for orthorectification of single-shot photographs of complex substrata, nor does it provide a clear definition of orthogonal when applied to complex benthic substrata. More importantly, the point-intercept method does not require orthorectification to generate abundance estimates that are quantitative and valid. When using the point-intercept method, higher accuracy of estimates of benthic abundance is dependent on greater replication. Reanalysis of mesophotic reef photographs by Lesser et al. (2023) resulted in a > 90% reduction in replication because useful images were rejected erroneously. Area-based metrics (biomass, density, size, etc.) of complex reef substrata can be done accurately with 3D photogrammetry using multiple images of the same subject area.