By Valerie Perini

Among the many threats facing coral reefs throughout the world, we can add to the list an encrusting sponge found in the Indian Ocean. The sponge, Terpios hoshinota, grows on top of reef-building corals, covering them so they cannot catch food, and their endosymbiotic algae cannot capture light to perform photosynthesis.

To make matters worse, the sponge is currently expanding its range by moving towards the western Indian Ocean. A new study by MSC PhD candidate Jennifer Elliott and Professor Mark Patterson characterizes the range expansion of the sponge while also providing a glimmer of hope that some corals might be able to survive the killer sponge.

In the study, published in the journal Marine Biodiversity, Elliott and colleagues conducted surveys on the coral reefs of Mauritius, in the southwestern Indian Ocean, documenting the first appearance of the coral-killing sponge in this region. The researchers measured the growth rate of the sponge as well quantified the total habitat area inhabited by the sponge in 2014.

Additionally, the researchers report that during their surveys, they encountered a species of reef-building coral that was able to successfully overgrow established sponge colonies. The coral, Montipora aequituberculata, was successful in outcompeting the sponge because it did not attempt to attack the growing end of the sponge. Researchers posit that the high growth rate and plasticity of M. aequituberculata helped the coral to out complete the sponge.

This study provides important information regarding a poorly understood threat to Indo-Pacific corals, and offers hope that some coral species may be able to survive the destructive colonization of the sponge.