27 years of benthic and coral community dynamics on turbid, highly urbanised reefs off Singapore.

J R Guest,A Vergés,A H Campbell,A G Bauman,L M Chou,K Tun,E M Marzinelli,P D Steinberg,J Low,D A Feary

doi:10.1038/srep36260

J R Guest, A Vergés + Show 8 more

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https://doi.org/10.1038/srep36260

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Abstract

Coral cover on reefs is declining globally due to coastal development, overfishing and climate change. Reefs isolated from direct human influence can recover from natural acute disturbances, but little is known about long term recovery of reefs experiencing chronic human disturbances. Here we investigate responses to acute bleaching disturbances on turbid reefs off Singapore, at two depths over a period of 27 years. Coral cover declined and there were marked changes in coral and benthic community structure during the first decade of monitoring at both depths. At shallower reef crest sites (3–4 m), benthic community structure recovered towards pre-disturbance states within a decade. In contrast, there was a net decline in coral cover and continuing shifts in community structure at deeper reef slope sites (6–7 m). There was no evidence of phase shifts to macroalgal dominance but coral habitats at deeper sites were replaced by unstable substrata such as fine sediments and rubble. The persistence of coral dominance at chronically disturbed shallow sites is likely due to an abundance of coral taxa which are tolerant to environmental stress. In addition, high turbidity may interact antagonistically with other disturbances to reduce the impact of thermal stress and limit macroalgal growth rates.

Highlights

Coral cover on reefs is declining globally due to coastal development, overfishing and climate change
Between 1988 and 2012 there was an overall ~12% decline in mean coral cover at the shallow sites, whereas at deep sites there was a decline of almost 30% between 1986 and 2012
Coral cover on Indo-Pacific reefs has declined dramatically in recent decades with some heavily disturbed reefs undergoing phase shifts from coral to algal dominance[5,6,16,54,55]

Summary

Introduction

Coral cover on reefs is declining globally due to coastal development, overfishing and climate change. Reef building corals may remain dominant following disturbances, but coral taxonomic community structure may shift towards species capable of tolerating new environmental conditions, resulting in novel assemblages[12,13]. The most common such change is a shift in dominance from susceptible taxa with branching morphologies, rapid growth rates and high structural complexity to taxa that have foliose or massive morphologies and slower growth rates[12,14,15]. It is generally accepted that chronic human disturbances compromise the ability of coral reefs to recover from acute disturbances[19], some heavily disturbed reefs appear surprisingly resilient[20]

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