REEFS HAPPEN

Corals and coral reefs confront us with a variety of paradoxes in term s of their responses to global change. The species appear evolutionari ly long-lived and stable, and combinations of organisms recur and pers ist at levels ranging from endosymbiosis to palaeocommunity structure. The fact that these organisms and communities occupy a seemingly prec arious environment near the common interface of land, sea, and air sug gests that they possess powerful adaptive and acclimative mechanisms, and the special characteristics associated with their range of reprodu ctive options, their modular (colonial) form, and their symbiotic asso ciations provide multiple pathways for adaptation. At the same time, t hey are widely considered to be vulnerable to anthropogenic stresses, and to show signs of deterioration on a global scale. Interest in cora ls is further enhanced by their unique position with regard to the car bon cycle, with inorganic and organic carbon metabolisms that are of c omparable magnitudes. The durable limestone structures they create mod ify the shallow-water environment, and their mineral skeletons preserv e in their isotopic, chemical, and structural characteristics records of past environmental conditions. Whether as survivors, recorders, or victims, their relationship to global change is fascinating and instru ctive. This paper provides a general background and context for the sp ecific papers that make up this topical issue of Global Change Biology .