The effect of substratum on the growth of Terpios, an encrusting sponge which kills corals

Abstract

The effects of substratum on the growth of Terpios was demonstrated using experimental and observational data at Guam, Mariana Islands. Terpios growth was measured on live coral, reef rock, and red calcareous algae in the field. In addition, Terpios was transplanted onto live coral, air-blasted (clean) coral, reef rock, and plexiglass plates, and subsequent growth measured. Terpios grows fastest on clean substrata followed by live coral, reef rock and red calcareous algae in decreasing order. Terpios is sometimes overgrown by Montipora, Porites and red calcareous algae. Since Terpios grows fastest when living coral tissue is removed, it is not likely that Terpios ingests coral tissue as previously suggested in the literature. Instead, Terpios is probably an efficient competitor of corals for space. Terpios overgrows most hard, stable reef substrata, and the growth rate on all sample substrata is substantial. Therefore Terpios has a great potential for covering a reef and may be one of the most important causes of disturbance on some coral reefs.