REEForm Thematic Programme 3: Reef carbonate production

Coral reefs and reef sedimentary landforms are unique in that they are composed predominantly of calcium carbonate (CaCO3) that results almost entirely from ecological processes. Corals typically represent the primary constructional components on most reefs, but significant amounts of additional carbonate are also produced by various calcareous encrusting organisms, by a wide range of benthic carbonate sediment producers, and through the precipitation of marine cements. In addition, a range of physical and biological processes also operate to directly erode the accumulating reef structure, this material subsequently either re-accumulating within the reef structure or being exported either to adjacent landforms (islands) or out of the reef system. These various carbonate producing and cycling processes strongly influence reef-related carbonate accumulation, and the relative importance of each, within a given reef system, controls net rates of carbonate accumulation (a concept defined by the carbonate budget approach to conceptualizing and quantifying reef geomorphic performance).

It is evident, however, that while our understanding of the organisms and processes involved in reef framework and sediment production is generally good, and our conceptual understanding of how these processes interact to drive reef accretion and/or generate sediment facies is also reasonably good, attempts to quantify the rates of production either cumulatively or for individual components are far more poorly constrained, and knowledge of sediment production and accumulation pathways remains limited. Major research gaps also clearly exist in terms of linking reef ecological states (and changes therein) to sediment and framework carbonate production rates and styles.

REEForms research activities under this Thematic Programme will thus focus on addressing the following:

  • The establishment of reef framework carbonate budget studies from a wider variety of sites than exist at present, including from reefs that exist across gradients of evolutionary states and from anthropogenically modified environments.
  • The development of standardized approaches to quantify rates of carbonate sediment production.
  • The establishment of more spatially representative island sediment records, especially where these can be linked both to estimates of contemporary production and to records of recent morphodynamic change.

These will help us to:

  • Provide an improved understanding of rates of reef carbonate production across gradients of both natural and anthropogenic environmental change.
  • Understand how sediment production and supply to reef islands changes through time as islands evolve.
  • Understand the major environmental factors than can trigger changes in sediment and framework carbonate production.
  • Inform the reef ecosystem change debate in terms of understanding the geomorphic consequences of changing carbonate production regimes.