Ascension Island’s Hermatypic but Non-Reef Building Corals

Abstract

Ascension Island lies 8° south of the equator in the South Atlantic and approximately 150 km west of the mid-Atlantic Ridge. The island has a stark beauty, with much of it resembling what one might imagine a martian landscape to look like: rugged brown lava flows and little vegetation. In spite of its tropical location, the island does not have palm-fringed shores nor does it have coral reefs – but why? Just five species of scleractinian coral have been identified, though these are either encrusting or solitary forms. Reasons for the paucity of marine invertebrates in the island’s near-shore waters are put forward, including the island’s isolation, the influence of oceanic currents affecting colonisation and the heavy grazing pressure from fish and sea urchins.