A comparative study of the cup reefs of Bermuda and the reefs of Green Lake, Fayetteville, New York, and of other central New York lakes indicates similarities in form and growth pattern. In both instances, algae are major contributors to growth.
The cup reefs, or “boilers,” grow near the margin of the Bermuda platform and rise 2 to 10 m from a coral floor to the intertidal zone. They are composed principally of encrusting calcareous red (coralline) algae and colonial vermetid gastropods. The material composing the reefs is primarily high-Mg calcite with lesser amounts of aragonite.
The algal reefs in Green Lake grow as lobate, overhanging ledges that protrude 2 to 8 m into the lake. The ledges extend from lake level to a depth of approximately 12 m. These reefs are composed of low-Mg calcite algal sediment and cement.
The same processes of sediment production, trapping, and cementation are at work in both environments but in differing proportions. In Green Lake, the main sediment producer is the calcareous alga Chara, which is analogous to the calcareous alga Liagora valida on the cup reefs. In the quiet waters of Green Lake, surface growth of the reef occurs by trapping and binding of sediment by blue-green algae and mosses, and later cementation is by precipitated calcium carbonate. In the cup reefs, trapping and binding is primarily confined to protected cavities, and surface growth in the agitated water is mainly by encrusting calcareous algae. In both environments, cementation continues inside cavities by precipitation of calcium carbonate.