Deficits in functional trait diversity following recovery on coral reefs

Abstract

The disturbance regimes of ecosystems are changing, and prospects for continued recovery remain unclear. New assemblages with altered species composition may be deficient in key functional traits. Alternatively, important traits may be sustained by species that replace those in decline (response diversity). Here, we quantify the recovery and response diversity of coral assemblages using case studies of disturbance in three locations. Despite return trajectories of coral cover, the original assemblages with diverse functional attributes failed to recover at each location. Response diversity and the reassembly of trait space was limited, and varied according to biogeographic differences in the attributes of dominant, rapidly recovering species. The deficits in recovering assemblages identified here suggest that the return of coral cover cannot assure the reassembly of reef trait diversity, and that shortening intervals between disturbances can limit recovery among functionally important species.

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

“…For example, the Great Barrier Reef has >420 coral species, of which 76 belong to the Acropora genus, while the Caribbean has a ~76 coral species, of which only three belong to the Acropora genus (Kuffner & Toth, 2016). This wide range of species and traits in the Indo‐Pacific has allowed the reefs of this region to be less affected by disturbances while showing an increased capacity for functional recovery (Denis et al., 2017; Januchowski‐Hartley et al., 2017; McWilliam et al., 2020). In addition, at the onset of our study, most of the reef sites were already dominated by the same species and traits, as they were at the conclusion of the study, and the contributions of species with key functional traits, such Acropora spp., were very low (Figure 4b,d; Figure S1), which may explain the observed maintenance of trait assemblages in our study.…”

Beyond coral-algal regimes: high taxonomic resolution surveys and trait-based analyses reveal multiple benthic regimes

“…Over the past four decades, tropical coral reefs, one of Earth's most biodiverse ecosystems, have experienced global declines and shifts in species compositions that deeply affect their functioning and the ecosystem services provided (Ainsworth and Mumby, 2015;Hughes et al 2018;McWilliam et al 2020). A turnover between highly three-dimensional scleractinian corals such as Acroporidae, by more robust corals (e.g.…”

Local Human Impacts Disrupt Relationships Between Benthic Reef Assemblages and Environmental Predictors

“…This may be a particular issue in regions such as the tropical Pacific where species diversity is exceptionally high and fleshy macroalgae, frequently stated as principal alternative organisms on degraded reefs, do not play such a dominant role in benthic dynamics compared, for instance, to the Caribbean region (Roff and Mumby, 2012). Furthermore, reefs are increasingly existing in a partially degraded condition between distinct regimes (Mumby, 2017), likely having undergone ecological homogenisation resulting from the non-random removal of species with particular traits in response to environmental factors (McWilliam et al, 2020). In this case, coral cover can remain moderate but comprises a less diverse community of stresstolerant and opportunistic types (Côté and Darling, 2010;van Woesik et al, 2011;Riegl et al, 2013).…”