Holocene coral reef rubble and its binding agents

A literature review regarding reef rubble (defined as mechanically or chemically abraded parts of framebuilders or reef rock larger than sand fraction) and its binding agents is presented. Rubble is produced by natural and man-made events such as storms, wave agitation, earthquakes, bioerosion, ship groundings, and dynamite fisheries. The regeneration of reefs after bubble-forming processes requires rigid rubble binding, which is always preceded by preliminary stabilization. Preliminary stabilization can be achieved by a decline in hydrodynamic energy, interlocking of components, seagrass, and overgrowth by sponges or algae. Rigid binding is primarily achieved by diagenetic cementation. The literature indicates that binding by coralline algae or other organisms (corals, worms, bryozoans) is only of subordinate importance. Highest rates of rigid rubble binding are known from fore-reef areas with low sloping angles above fair-weather wave base; rigid rubble binding is particularly rare in deeper fore-reef environments and not described from the reef crest. Rigid binding by diagenetic cementation is generally known from inter- and supratidal near-shore ramparts as well as back-reef, reef-flat, and shallow fore-reef rubble accumulations, while coralline algae rigidly bind rubble only in very shallow fore-reef environments. Rubble binding does not appear to be easily achieved and fewer reports of bound rubble were found than of loose rubble.