Coral Reef Growth in the Galapagos: Limitation by Sea Urchins

The regular echinoid Eucidaris thouarsii is a conspicuous omnivore on coral bottoms in the Galapagos. Unlike Eucidaris in Panama and mainland Ecuador, Galapagos Eucidaris are large and abundant and graze heavily in the open on live corals day and night. These differences are probably due in large part to more intense predation by fishes on mainland compared with island urchin populations. An assessment of coral growth versus coral attrition from grazing shows that Eucidaris interferes with the establishment of pocilloporid reef frame and therefore reduces reef growth in the Galapagos.