10. Introduction to Bermuda: Geology, Oceanography and Climate

The Bermuda islands and shallow platform lie on the top of an extinct Meso-Cenozoic volcano. The islands and the Bermuda Platform were created by reef building corals, vermetid snails and calcareous algae that colonized the eroding seamount. Coral reefs even played a significant role in the settlement of Bermuda and now human impacts of the well-populated islands are important to the ongoing health of the reefs and coral communities. The economic underpinnings of Bermuda – financial services and tourism, along with limited agriculture and small fisheries have created a society that has a moderate impact on the reefs and has a significant and direct economic interest in maintaining a healthy marine environment. Throughout the history of Bermuda, the distribution of coral reefs, and coral communities on the Platform have been determined by the interactions of several environmental factors. Pleistocene formations underlie many modern reefs and there is evidence of submerged reef tracts at depths below 60 m, all around the Bermuda Pedestal. The positions of these formations correspond to stable sea level positions attained during glacial and interglacial periods. Today, there is great variability in the marine environment on the Platform, with the most extreme conditions occurring in inshore waters. The most extensive reefs are developed around the shallow rim of the Platform and, seaward from this, down a gradually descending slope to about 50–60 m depth. Algal-vermetid cup reefs are particularly abundant in Bermuda. On the Platform, seagrass and calcareous green algae beds are closely associated spatially and ecologically with coral reefs, forming unique communities; these are widespread across the lagoon and larger inshore water bodies.