No abstract

The purpose of this study is to examine the rate of growth of reef-building corals by measuring the calcium deposition in the skeleton with the aid of a new method using radioactive calcium-45 as tracer. With this procedure it was possible to determine calcification rates in the different parts of coral colonies, and to estimate quantitatively the effect of light and darkness, zooxanthellae and carbonic anhydrase inhibitors on skeletogenesis.Numerous attempts have been made in the past to estimate the growth rates of reef-building corals, mostly by letting weighed and measured coral colonies grow in their natural habitat for periods of months to years (Agassiz

Very extensive bleaching of coral reef communities occurred after severe flood rains over eastern Jamaica. The loss of color was due to the mass expulsion of zooxanthellae from the tissues of Millepora, Scleractinia, Zoanthidea, and Actiniaria living in the shallow reef zones. The polyps of the bleached individuals continued to expand and feed in their normal fashion. It is believed that expulsion of the zooxanthellae was induced by contact with water of lowered osmotic pressure on the surface of the sea, rather than by sedimentation or fouling. Regeneration of the depleted zooxanthellar populations was very slow; many of the bleached colonies survived well despite the near total absence of zooxanthellae from their tissues for over 2 months.

No abstract

Brachiopods and coralline sponges are the dominant taxa of a series of parallel pantropical communities found in cryptic habitats of Recent coral reefs, where these organisms may cover almost the entire available surface area. It is suggested that the continued survival and success of these and other groups of considerable paleontological importance resulted from their occupation of cryptic reef habitats after competition with more rapidly growing hermatypic corals in the Middle Jurassic when scleractinian reefs first appeared.