Abstract Summary
Despite widespread increases in coral outplanting around the globe, few studies focus on the effects of coral restoration on reef communities or important ecosystem functions like herbivory and coral predation. Here, we measured the impact of coral restoration at four reefs in the Florida Keys, USA, ranging from 2-11 years of coral outplanting. To move beyond focusing on outplanted corals, we examined differences in three major criteria: diversity, community structure, and ecological processes, via paired surveys of restored sites where corals had been outplanted and unmanipulated control sites. Coral restoration successfully enhanced coral populations, increasing coral cover 4-fold compared to control sites. Surprisingly, there were few changes in the coral and fish communities with restoration. Some restored sites had higher abundance of herbivorous fish, higher rates of herbivory, or more juvenile-sized corals, but these effects were limited to individual reefs. Higher densities of territorial damselfishes in restored sites emerged as the consistent difference in fish communities. Corallivorous snails were 1.6x more abundant on corals in restored sites compared to control sites, and disease and mortality were more prevalent in restored areas. Thus, despite successfully augmenting target populations, coral restoration at these sites does not appear to have facilitated positive feedbacks that help reinforce coral success. Although coral restoration can successfully boost the cover of corals at degraded sites, additional restoration strategies are likely needed to realize community-level benefits of coral restoration and restore key functions like herbivory. We advocate for harnessing ecological processes that drive community dynamics on coral reefs in a way that facilitates the establishment and growth of restored corals. Drawing on decades of coral reef ecology research and lessons learned from the restoration of other ecosystems, we posit that restoration practitioners can control factors such as the density, diversity, and identity of transplanted corals; site selection; and transplant design to restore positive feedback processes – or to disrupt negative feedback processes – in order to improve restoration success. Ultimately, we argue that coral restoration should explicitly incorporate key natural processes to exploit dynamic ecological forces and drive recovery of coral reef ecosystems.
