Structure-from-motion (SfM) photogrammetry is a technique used to generate threedimensional (3D) reconstructions from a sequence of two-dimensional (2D) images.SfM methods are becoming increasingly popular as a noninvasive way to monitor many systems, including anthropogenic and natural landscapes, geologic structures, and both terrestrial and aquatic ecosystems. Here, a detailed protocol is provided for collecting SfM imagery to generate 3D models of benthic habitats. Additionally, the cost, time efficiency, and output quality of employing a Digital Single Lens Reflex (DSLR) camera versus a less expensive action camera have been compared.A tradeoff between computational time and resolution was observed, with the DSLR camera producing models with more than twice the resolution, but taking approximately 1.4-times longer to produce than the action camera. This primer aims to provide a thorough description of the steps necessary to collect SfM data in benthic habitats for those who are unfamiliar with the technique as well as for those already using similar methods.

The structural complexity of coral reefs provides important ecosystem functions, such as wave attenuation for coastal protection, surfaces for coral growth, and habitat for other organisms. Corals build much of this structure, but an understanding of how colonies of different species and sizes contribute to complexity is lacking. We quantified three interdependent descriptors of complexity-rugosity, fractal dimension, and height range-for reef patches as well as the corals growing upon them in Ka ¯ne'ohe Bay (O'ahu, Hawai'i). Despite similar levels of reef-scale complexity throughout the bay, we found marked differences in how species contribute to this complexity. Variation in complexity among species was closely tied to colony morphology, but not to colony size. Together, our results show that no one species is sufficient to generate the full spectrum of habitat complexities we see on coral reefs, which has direct implications for reef recovery and restoration.