Recovery disparity between coral cover and the physical functionality of reefs with impaired coral assemblages

Abstract

The ecology and structure of many tropical coral reefs have been markedly altered over the past few decades. Although long‐term recovery has been observed in terms of coral cover, it is not clear how novel species configurations shape reef functionality in impaired reefs. The identities and life‐history strategies of the corals species that recover are essential for understanding reef functional dynamics. We used a species identity approach to quantify the physical functionality outcomes over a 13 year period across 56 sites in the Mexican Caribbean. This region was affected by multiple stressors that converged and drastically damaged reefs in the early 2000s. Since then, the reefs have shown evidence of a modest recovery of coral cover. We used Bayesian linear models and annual rates of change to estimate temporal changes in physical functionality and coral cover. Moreover, a functional diversity framework was used to explore changes in coral composition and the traits of those assemblages. Between 2005 and 2018, physical functionality increased at a markedly lower rate compared to that of coral cover. The disparity between recovery rates depended on the identity of the species that increased (mainly non‐framework and foliose‐digitate corals). No changes in species dominance or functional trait composition were observed, whereas non‐framework building corals consistently dominated most reefs. Although the observed recovery of coral cover and functional potential may provide some ecological benefits, the long‐term effects on reef frameworks remain unclear, as changes in the cover of key reef‐building species were not observed. Our findings are likely to be representative of many reefs across the wider Caribbean basin, as declines in coral cover and rapid increases in the relative abundance of weedy corals have been reported regionally. A coral identity approach to assess species turnover is needed to understand and quantify changes in the functionality of coral reefs.

Effects of the Stony Coral Tissue Loss Disease Outbreak on Coral Communities and the Benthic Composition of Cozumel Reefs

“…In addition, the loss of highly susceptible coral species may also trigger an abrupt decrease in the accretion (growth) of the reef framework (Estrada-Saldívar et al, 2020), as most of the highly susceptible species to SCTLD are also important reef builders. A shift in the composition of reefbuilding corals and reef structure may not only compromise ecosystem resilience through a reduction in functional traits (González-Barrios et al, 2020;Molina-Hernández et al, 2020) but may also affect many other reef-associated species (Idjadi and Edmunds, 2006;Rogers et al, 2014). Given the short-temporal scale of our study, we cannot conclude that the drastic changes observed in the ecological communities will lock Cozumel reefs into low-carbonate production and high algae dominated states.…”

Different population trajectories of two reef‐building corals with similar life‐history traits

“…Red lines represent the mean of 500 stochastic projections (depicted as thin light red lines) based on the population growth rate (λ) derived from the IPMs with fecundity reduced to half (λ = 1.038 for D. favus and λ = 0.948 for P. lamellina) traits frequently express ecological functionality (Madin et al, 2016;Mouillot et al, 2013), there is an increasing interest in heuristically categorizing corals for comparative purposes. For example, some studies emphasize 'weedy' versus 'non-weedy' (Knowlton, 2001), or massive versus branching morphologies (Álvarez-Noriega et al, 2016;Comeau et al, 2014;Klepac & Barshish, 2020;Loya et al, 2001;Pisapia et al, 2020), or some other multi-dimensional trait measures (Darling et al, 2012;Denis et al, 2017;González-Barrios et al, 2020;van Woesik, Franklin, et al, 2012). In most cases, studies using trait categories largely aim to estimate 'winners' and 'losers' (sensu Loya et al, 2001), or differential functionality following disturbances and ecosystem-wide changes (Denis et al, 2017;González-Barrios et al, 2020;Mouillot et al, 2013).…”

“…For example, some studies emphasize 'weedy' versus 'non-weedy' (Knowlton, 2001), or massive versus branching morphologies (Álvarez-Noriega et al, 2016;Comeau et al, 2014;Klepac & Barshish, 2020;Loya et al, 2001;Pisapia et al, 2020), or some other multi-dimensional trait measures (Darling et al, 2012;Denis et al, 2017;González-Barrios et al, 2020;van Woesik, Franklin, et al, 2012). In most cases, studies using trait categories largely aim to estimate 'winners' and 'losers' (sensu Loya et al, 2001), or differential functionality following disturbances and ecosystem-wide changes (Denis et al, 2017;González-Barrios et al, 2020;Mouillot et al, 2013). While such approaches yield valuable insights, they amalgamate species (or even genera), which may result in the loss of subtle yet different speciesspecific responses, as shown here.…”

“…Despite the value of coral cover as a key metric of assessing a coral-reef state, changes in coral cover alone cannot accurately predict species-specific population trajectories Hartmann et al, 2018;Ortiz et al, 2018;Pisapia et al, 2020;Shlesinger & Loya, 2019). For example, coral composition at any one location can change from one assemblage to another, or change from high to low diversity, or from a few large colonies to many small colonies-while not displaying obvious changes in coral cover (Done, 1999;Fine et al, 2019;González-Barrios et al, 2020;Knowlton, 2001;Pisapia et al, 2020).…”

The transformation of Caribbean coral communities since humans

“…The increasing occurrence of some stress-tolerant and weedy corals (Agaricia, P. astreoides, branching Porites) over the past four decades in the midslope zone corresponds to trends in percent living cover from modern localized surveys of Caribbean coral communities (Green et al, 2008, Estrada-Saldívar et al, 2019, González-Barrios et al, 2021.…”