Changing geo‐ecological functions of coral reefs in the Anthropocene

Abstract

The ecology of many coral reefs has changed markedly over recent decades in response to various combinations of local and global stressors. These ecological changes have important implications for the abundance of taxa that regulate the production and erosion of skeletal carbonates, and thus for many of the geo‐ecological functions that coral reefs provide, including reef framework production and sediment generation, the maintenance of reef habitat complexity and reef growth potential. These functional attributes underpin many of the ecosystem goods and services that reefs provide to society. Rapidly changing conditions of reefs in the Anthropocene are likely to significantly impact the capacity of reefs to sustain these geo‐ecological functions. Although the Anthropocene footprint of disturbance will be expressed differently across ecoregions and habitats, the end point for many reefs may be broadly similar: (a) progressively shifting towards net neutral or negative carbonate budget states; (b) becoming structurally flatter; and (c) having lower vertical growth rates. It is also likely that a progressive depth‐homogenisation will occur in terms of these processes. The Anthropocene is likely to be defined by an increasing disconnect between the ecological processes that drive carbonate production on the reef surface, and the net geological outcome of that production, that is, the accumulation of the underlying reef structure. Reef structures are thus likely to become increasingly relict or senescent features, which will reduce reef habitat complexity and sediment generation rates, and limit reef potential to accrete vertically at rates that can track rising sea levels. In the absence of pervasive stressors, recovery of degraded coral communities has been observed, resulting in high net‐positive budgets being regained. However, the frequency and intensity of climate‐driven bleaching events are predicted to increase over the next decades. This would increase the spatial footprint of disturbances and exacerbate the magnitude of the changes described here, limiting the capacity of many reefs to maintain their geo‐ecological functions. The enforcement of effective marine protection or the benefits of geographic isolation or of favourable environmental conditions (“refugia” sites) may offer the hope of more optimistic futures in some locations. A >plain language summary is available for this article.

The meaning of the term ‘function’ in ecology: A coral reef perspective

“…consumption rate per individual), to provide an overall estimate of the magnitude of a function over a unit area (e.g. rates of grazing on reefs or bioerosion m −2 ) (Bellwood et al, ; Graham et al, ; Perry & Alvarez‐Filip, ). The advantage of this approach is that functional impacts can be estimated at an individual, population, species, functional group or community level and can be expressed as a rate‐based process in terms of its spatial impact (function per unit area).…”

Tropicalisation of temperate reefs: Implications for ecosystem functions and management actions

“…In particular, acidification tends to increase coral reef bioerosion, preventing effective reef accretion (Barkley et al, ), and this may be further accentuated by higher nutrients (e.g., due to increases in current‐driven upwelling; Schaeffer, Roughan, & Wood, ), which can impair coral skeletal density and limit reef construction (Manzello et al, ). This suggests that high latitude coral‐dominated reefs of the future may not form accreting reef frameworks (Perry & Alvarez‐Filip, ), and this may limit associated biodiversity. Ocean acidification may also limit corals by enhancing the competitive strength of turf and seaweeds generally (Connell & Russell, ; Diaz‐Pulido, Gouezo, Tilbrook, Dove, & Anthony, ) and of kelp in particular (Linares et al, ).…”

Coral reef ecology in the Anthropocene

“…Globally, human‐induced warming of the ocean is resulting in increasingly frequent mass coral bleaching events (Hughes, Anderson et al, ) that are transforming coral assemblages (Hughes, Kerry et al, ) and in some cases causing regime shifts to fleshy macroalgae (Graham, Jennings, MacNeil, Mouillot, & Wilson, ). In combination with human‐induced ocean acidification (Albright et al, ), these shifts in benthic composition have broader ecosystem effects, from compromising the growth of reef structures (Perry & Alvarez‐Filip, ; Perry et al, ) to changing the diversity, abundance and behaviour of other reef‐associated organisms (Keith et al, ; Richardson, Graham, Pratchett, Eurich, & Hoey, ; Stuart‐Smith, Brown, Ceccarelli, & Edgar, ). Hence, myriad interconnected human drivers are rapidly changing the structure and function of reefs (Pendleton, Hoegh‐Guldberg, Langdon, & Comte, ).…”