Persistence and Change in Community Composition of Reef Corals through Present, Past, and Future Climates

Abstract

The reduction in coral cover on many contemporary tropical reefs suggests a different set of coral community assemblages will dominate future reefs. To evaluate the capacity of reef corals to persist over various time scales, we examined coral community dynamics in contemporary, fossil, and simulated future coral reef ecosystems. Based on studies between 1987 and 2012 at two locations in the Caribbean, and between 1981 and 2013 at five locations in the Indo-Pacific, we show that many coral genera declined in abundance, some showed no change in abundance, and a few coral genera increased in abundance. Whether the abundance of a genus declined, increased, or was conserved, was independent of coral family. An analysis of fossil-reef communities in the Caribbean revealed changes in numerical dominance and relative abundances of coral genera, and demonstrated that neither dominance nor taxon was associated with persistence. As coral family was a poor predictor of performance on contemporary reefs, a trait-based, dynamic, multi-patch model was developed to explore the phenotypic basis of ecological performance in a warmer future. Sensitivity analyses revealed that upon exposure to thermal stress, thermal tolerance, growth rate, and longevity were the most important predictors of coral persistence. Together, our results underscore the high variation in the rates and direction of change in coral abundances on contemporary and fossil reefs. Given this variation, it remains possible that coral reefs will be populated by a subset of the present coral fauna in a future that is warmer than the recent past.

Evaluating the causal basis of ecological success within the scleractinia: an integral projection model approach

“…This emphasis has been characterized by limited progress in evaluating the causal basis of ecological success or failure among coral taxa (Loya et al 2001), and therefore provides a compelling context within which new approaches can be proposed. It is widely accepted that "weedy" corals will fare better than "nonweedy" corals on the reefs of tomorrow (Knowlton 2001), and that thermal resilience will be critical for survival in a warmer future (Brown and Cossins 2011;Edmunds et al 2014). These traits, however, have not been evaluated in the context of impacts on long-term demography such as the population growth factor λ, nor have they been evaluated for relative importance against one another.…”

“…Further, a trait-based analysis of coral performance over ecological (i.e., on extant reefs) and geological time (i.e., the fossil record) revealed that the evolutionary fate of coral species was largely independent of taxon. We inferred, therefore, that the fate of corals was more strongly dependent on holobiont phenotypes than taxonomy, and subsequently implemented a modeling effort to evaluate the features of winning and losing corals in a phenotype-based construct (Edmunds et al 2014). …”

“…The present paper originated as an effort to use empirical data describing coral phenotypes to codify our general phenotype-based model projecting present-day reefs into a future of warmer and more acidic seas (Edmunds et al 2014). Conceptually, we intended to select corals identified as ecological winners or losers based on changes in their absolute and relative abundance on contemporary reefs between 1981 and 2010 (Edmunds et al 2014), and then define their phenotypes based on continuously distributed measurements of select traits.…”

“…Conceptually, we intended to select corals identified as ecological winners or losers based on changes in their absolute and relative abundance on contemporary reefs between 1981 and 2010 (Edmunds et al 2014), and then define their phenotypes based on continuously distributed measurements of select traits. Our objective was to use the ecological categories and their corresponding phenotypic properties as parameter values in a population model from which we could evaluate emergent properties of the population.…”

“…A demographic approach to defining ecological success offers advantages over common measures of abundance (like percentage cover), which are related only loosely to demographic processes (Hughes and Tanner 2000;Edmunds and Elahi 2007;Darling et al 2013). Stable coral cover can, for example, hide impending population decline (Hughes and Tanner 2000), and categorizing corals based on changes in cover (Loya et al 2001;Edmunds et al 2014) has the potential to generate functional groupings with equivocal ecological relevance.…”