Implications of reef ecosystem change for the stability and maintenance of coral reef islands

Abstract

Abstract.Coral reef islands are amongst the most vulnerable environments on Earth to climate change because they are low lying and largely constructed from unconsolidated sediments that can be readily reworked by waves and currents. These sediments derive entirely from surrounding coral reef and reef flat environments and are thus highly sensitive to ecological transitions that may modify reef community composition and productivity. How such modificationsdriven by anthropogenic disturbances and on-going and projected climatic and environmental change -will impact reef island sediment supply and geomorphic stability remains a critical but poorly resolved question. Here we review the unique ecological -geomorphological linkages that underpin this question and, using different scenarios of environmental change for which reef sediment production responses can be projected, explore the likely resilience of different island types. In general, sand-dominated islands are likely to be less resilient than those dominated by rubble grade material. However, because different islands typically have different dominant sediment constituents (usually either coral, benthic foraminifera or Halimeda) and because these respond differently to individual ecological disturbances, island resilience is likely to be highly variable. Islands composed of coral sands are likely to undergo major morphological change under most near-future ecological change scenarios, whilst those dominated by Halimeda may be more resilient. Islands composed predominantly of benthic foraminifera (a common state through the Pacific region) are likely to exhibit varying degrees of resilience depending upon the precise combination of ecological disturbances faced. The study demonstrates the critical need for further research bridging the ecological-geomorphological divide in order to understand: 1) sediment production responses to different ecological and environmental change scenarios; and 2) dependant landform vulnerability.

Evolution of Coral Rubble Deposits on a Reef Platform as Detected by Remote Sensing

“…Strategic management founded on thorough science is urgently needed to assess and increase the resilience of coral reef ecosystems, particularly in the view of unprecedented anthropogenic disturbances [2]. Different branches of science take a differing view on the concept of stability on coral reefs: while ecologists maintain that coral reefs are fragile environments, geologists portray them as robust landforms [3][4][5]. However, the concept of stability depends largely on the spatio-temporal domain used for analysis, as reefs can appear both as resilient landforms over geological timescales, or fragile systems due to rapid changes over ecological timescales [6].…”

Reef Island Evolution and Dynamics: Insights from the Indian and Pacific Oceans and Perspectives for the Spermonde Archipelago

“…Differences in sediment accumulation patterns between islands can be partly explained through temporal transitions/variations in sediment supply during island formation and recognition that the relationship between reef production and sediment generation is not linear (Perry et al, 2011). Changes in sediment generation are therefore, likely to reflect alterations in the delicate balance between reef growth and productivity through time.…”

“…It is widely perceived that the reef "carbonate factory" yields a quasicontinual supply of sediment to build or maintain landforms. However, existing studies indicate that the composition and supply of detrital sediment available for island formation can vary temporally as a consequence of changes in reef growth/reef ecology (Yamano et al, 2000;Woodroffe, 2008;Perry et al, 2011) and these in turn influence the pattern of island accumulation.…”

Morphological characterisation of reef types in Torres Strait and an assessment of their carbonate production

“…within a whole-reef or between reefs) over time, effectively linking ecological and morphological changes (Buddemeier and Smith, 1988;Perry et al, 2008). However, current understanding of ecomorphodynamic interactions remain poorly resolved, with anticipated shifts in ecological processes due to climate change, adjustments in sediment production and transport that will affect associated landforms such as reef islands, and further implications for reef morphology (Perry et al, 2011).…”