Successful application of knowledge about modern reef ecosystems to Tertiary reef paleoecocystems depends greatly upon the scale at which it is applied.

The present is clearly an imperfect key to the past in the comparison of the biogeography and regional ecology of modern reefs with those of the Tertiary. This is largely because the Holocene and Pleistocene ecologic and biogeographic distribution of reef-building scleractinian corals, octocorals, and other key members of the reef community is a relatively recent phenomenon and is not representative of most of the Tertiary. Major changes in reef-coral paleobiogeography and evolution occurred in the late Eocene, at the end of the Oligocene, in the middle Miocene and at the end of the Pliocene. A worldwide change in the ecology of shallow-reef communities occurred in the early Pleistocene with the great diversification and growth luxuriance of predominantly branching species of reef-cor ls with light, rapidly growing skeletons accompanied by the proliferation of the hydrozoan Millepora. Most of these corals belong to the families Acroporidae, Poritidae, and Seriatoporidae.

Other more detailed paleoecologic relations may, however, be reconstructed only by strict uniformitarian comparison to living-reef examples because the evidence needed to derive them is not preserved or is incompletely preserved in the fossil record. Some of these include: (a) quantitative estimation for an ancient reef of the standing crop biomass volume and productivity. Many of the biotic components of the benthic reef ecosystem, such as seagrasses, sponges, and octocorals, have little preservation potential; (b) an estimation of the amounts and pathways of energy cycled through the benthic reef paleoecosystems; (c) the presence of symbiotic relations, such as the vital link between hermatypic corals and zooxanthellae; (d) mutualistic and antibiotic relations among encrusters; (e) ediment-rejection potential, especially that of reef corals, octocorals, and sponges; and (f) interspecific aggression among reef corals, although some overgrowth relations may be deduced from the fossil record.

End_of_Article - Last_Page 709------------