Award: OCE-1851510

Coral reefs provide habitat for fishes and invertebrates, but those animals can also help sustain the corals that shelter them. This project examined these two-way interactions on the reefs of Mo'orea, French Polynesia. We asked how the size and arrangement of branching coral colonies affect their resident animals, and how those animals, in turn, affect coral growth and recovery from disturbance.
We combined surveys of natural coral colonies, field experiments that changed coral size and spacing, three-dimensional measurements reconstructed from photographs, and mathematical models. The experiments showed that the arrangement of coral colonies changed the communities of fishes and invertebrates living within them. Isolated corals accumulated more beneficial residents and grew more than corals in denser neighborhoods. These results show why the amount of coral habitat alone may not predict the benefits that resident animals provide: neighboring colonies can influence which animals arrive and how many survive.
The models helped explain how these patterns can arise. Young animals settling onto the reef can be redirected among neighboring corals, changing the number reaching each colony. Survival after settlement can limit these effects when crowding increases mortality. A synthesis of studies of young reef fishes found that variation in this crowding-related mortality was greater within species than between species. A separate model of coral-animal mutualisms predicted that animals would preferentially settle on larger corals, even though settlement on smaller corals could improve recovery after disturbance. These are model predictions that identify questions for future experiments, rather than demonstrations that a particular restoration strategy will succeed.
The project also developed and evaluated methods for measuring coral growth and structure from photographs. Reviews brought together evidence on how coral-associated animals benefit their hosts, including protection and nutrient supply. Other publications examined methods for observing fish cleaning interactions and the reliability of ecological meta-analyses. Together, these studies improved tools for studying reef interactions and interpreting ecological evidence.
The award supported graduate and undergraduate researchers at UC Santa Barbara, the University of Georgia, and Tulane University, along with early-career researchers and technical staff. Participants gained experience in field and laboratory research, image processing, ecological modeling, data analysis, archiving, and scientific communication. Graduate researchers completed thesis or dissertation work, and undergraduate researchers contributed to fieldwork, video analysis, presentations, and data analysis.
Public engagement connected the research with educators and communities. The team worked with the 'Ātiti'a Center in Mo'orea to develop videos for elementary-school teachers featuring graduate researchers, underwater footage, and explanations of experiments. Local collaborators dubbed the videos in Tahitian and provided English subtitles. Project-related activities also included quantitative STEM education resources through QUBES and participation in "Imagination Squared," a community project about resilience. Conversations with Coral Gardeners connected the findings with questions about coral restoration.
Five datasets from the coral surveys and experiments were submitted to the Biological and Chemical Oceanography Data Management Office in March 2026 and accepted for further processing. At the most recent archive check on October 7, 2026, all five were listed as preliminary and in progress. The project's findings can inform future reef management and restoration by showing how coral arrangement and resident animals jointly affect coral performance.

Last Modified: 10/13/2026
Modified by: Adrian C Stier