Most marine sponges precipitate silicate skeletal elements, and it has been predicted that they would be among the few “winners” among invertebrates in an acidifying, high-CO2 ocean. But members of Class Calcarea and a small proportion of the Demospongiae have calcified skeletal structures, which puts them among those calcifying organisms which are vulnerable to lowered pH and CO3= availability.
Excavating sponges are prominent bioeroders on coral reefs that in comparison to other benthic organisms may suffer less or may even benefit from warmer, more acidic and more eutrophic waters. Here, the photosymbiotic excavating sponge Cliona orientalis from the Great Barrier Reef was subjected to a prolonged simulation of both global and local environmental change: future seawater temperature, partial pressure of carbon dioxide (as for 2100 summer conditions under "business-as-usual" emissions), and diet supplementation with particulate organics.