BIOLOGICAL VERSUS PHYSICO-CHEMICAL FORCING OF PHANEROZOIC REEF EVOLUTION

The strong link of modern tropical coral reef distribution with sea surface temperature and nutrient levels, led to the paradigm of a vulnerable ecosystem strongly controlled by changes in the abiotic earth system. However, rigorous statistical tests of a large database on Phanerozoic reefs (PaleoReefs) suggest that proxies for physico-chemical changes are rarely cross-correlated with changes in global reef distribution, abundance and intrinsic ecological properties. Although it is possible that abiotic factors drive the evolution of reefs, which are currently not measurable, the currently most parsimonious explanation is that biological factors are more important. One such factor is biodiversity, which can be shown to affect the ecological stability of reefs over millions of years. However, although reef-diversity fluctuated strongly without a pronounced underlying trend, there is a long-term trend of lesser ecological change in younger reefs. This suggests that either changes in the earth system were more pronounced in the distant past, or older reefs were more vulnerable to abiotic forcing than younger reefs.