Use of Bayesian analysis with individual‐based modeling to project outcomes of coral restoration

Abstract

Various approaches to coral restoration have been developed to help increase rate of reef recovery from perturbations, among the most common of which is coral transplantation. Success is often evaluated based on short-term observations that capture only the initial phase of space colonization by coral transplants. Here, an individual-based model is developed to quantify uncertainty in future trajectories in experimental plots given past observations. Empirical data were used to estimate probabilistic growth, survival, and fission rates of Acropora pulchra and A. intermedia (order Scleractinia) in a sandy reef flat (Bolinao, Philippines). Simulations were initialized with different densities (25 or 50 transplants per species per 16 m 2 ) to forecast possible coral cover trajectories over a 5-year period. Given current conditions, there is risk of local extinction which is higher in low-density plots for both species, and higher for A. intermedia compared to A. pulchra regardless of density. While total coral cover is projected to increase, species composition in the future is more likely to be highly uneven. The model was used to quantify effect on recovery rate of protection from pulse anthropogenic disturbances, given different initial transplantation densities. When monitoring data are limited in time, stochastic models may be used to assess whether the restoration trajectory is heading toward the desired state and at what rate, and foresee system response to various adaptive interventions. Implications for Practice• Coral cover may be restored in reef patches of several square meters after physical disturbance if the latter will not recur. • Members of the genus Acropora (order Scleractinia) are potential candidates for restoration because they grow quickly and can effectively reproduce asexually, provided local environmental conditions are suitable. • Differences exist among Acropora species in terms of growth and survival as well as competitive ability, factors that should be considered when choosing an appropriate combination, and transplant density of species to initiate coral population and community development in previously degraded reef areas.

Optimizing return‐on‐effort for coral nursery and outplanting practices to aid restoration of the Great Barrier Reef

“…Favia spp., Goniastrea spp., and others) RRE scores, presumably since not all K ‐selected histories are the same (Darling et al ). Different RRE scores for alternate morphologies of Acropora similarly demonstrates that not all r ‐selected life histories are equal (see also Sleeman et al ; Benjamin et al ). Values for both % Growth and % Survivorship were highly variable among morphologies of Acropora , resulting in RRE scores ranging from approximately 10–14.…”

“…Values for both % Growth and % Survivorship were highly variable among morphologies of Acropora , resulting in RRE scores ranging from approximately 10–14. Consequently, a single RRE score is insufficient to consider propagation success for Acropora as a genus, not only as a result of competition between growth forms of Acropora (Benjamin et al ) but also inherent differences in stress susceptibility (Hoogenboom et al ). For example, within the genus Acropora , “ Acropora plating” (largely Acropora hyacinthus ) and “ Acropora Branching Open” had lower and higher RRE scores, respectively.…”

A potential method for improving coral self‐attachment

“…Recently, there have been increasing efforts to restore reefs using sexually propagated corals (Guest et al , ; Chamberland et al ; Edwards et al ; dela Cruz & Harrison ). However, coral reef rehabilitation usually involves transplanting asexually propagated coral fragments that have been grown out in a nursery, similar to silviculture (Epstein et al ; Rinkevich ), and generally shows high variability in restoration outcomes (Barton et al ; Benjamin et al ). Transplantation methods must minimize the detachment losses to achieve success (Gomez et al ).…”

Rebutting the inclined analyses on the cost‐effectiveness and feasibility of coral reef restoration

“…The third postulation made by Bayraktarov et al (2016) was the contrived summation and averaging of the entire set of experiments and research scenarios, an approach that often leads to wrong conclusions. Coral reef restoration is a fledgling discipline, still inclined to different approaches (Rinkevich 2005, Benjamin et al 2017) that diverge in rationales, practices, and the intensity of the studies. Analyses performed with such raw material are prone to bias conversion when amalgamated with less representative results or when combining the results of diverged individual restoration acts/experiments.…”

“…The same holds true for other ecological engineering tactics (Lirman and Schopmeyer 2016): the creation of stocks of sexually derived spats in an attempt to augment population genetic repertoires (Linden and Rinkevich 2017); the "design" of coral chimeras from aggregated conspecific spats, which leads to enhanced survivorship, increased body size, an earlier onset of reproduction, and reduced predation risk (Linden and Rinkevich 2017); the long-term ecological engineering tool of supplying coral reefs with larvae through the transplantation of nurseryfarmed gravid colonies (Horoszowski-Fridman et al 2011); the successful integration of coral transplants into a degraded reef; the provision of new ecological niches for reef-associated fauna, fish, and invertebrates (Horoszowski-Fridman et al 2015); the construction of novel coral reef communities that are more impervious to global change conditions , Gillson et al 2013; and the creation of new connectivity routes and biological corridors via a series of mid-water coral nurseries arranged as stepping stone instruments (Rinkevich 2015a). Even different initial transplant densities have divergent success projections (Ladd et al 2016, Benjamin et al 2017, outcomes that are influenced by life-history tradeoffs (Montero-Serra et al 2017). The aforementioned examples further attest to the surplus benefits that develop on top of the enhanced coral survival and growth rates, simply by enhancing the reproduction efforts and larval development and settlement, as well as the corals' post-settlement survivorship and development (Rinkevich 2015a, Lirman andSchopmeyer 2016).…”