The contribution of corals to reef structural complexity in Kāne‘ohe Bay

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 Kāne‘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.