The development of a marine community (the ecological succession or sere) shows the same trends in the Silurian (as described by Lowenstam in the case of Niagaran reefs of the Great Lakes area) as occurs today. Three stages in the reef development are the quiet-water stage (pioneer community), the semi-rough-water stage (pre-climax community), and the rough-water or wave-resistant stage (climax community). The first stage is simple in biotic composition, with comparatively few species, classes, and phyla present. Increase in variety and total population of organisms typifies the change to the second stage. The final stage is marked by the presence of a very complex biotic association. In the first stage, Stromatactis-like forms are dominant, in the second and third a stromatoporoid species is dominant, with one or more species of crinoids and brachiopods as subdominants. A much greater number of species, genera, orders, classes, and phyla lived in the reef area during the climax than during the pioneer stage.

You do not currently have access to this article.