Buoyant weight, chemical bioerosion, and mechanical bioerosion from sponge ocean acidification study; sponges collected in Florida Keys and State Waters of Miami Dade (NCEI Accession 0276485)

Coral reef ecosystems are experiencing increased rates of dissolution due to the impacts of ocean acidification (OA) on coral reef calcifiers and bioeroders. Here, we subjected common zooxanthellate (Cliona varians) and azooxanthellate (Pione lampa) Caribbean sponges to four pH treatments: pre-industrial (8.15), present-day (8.05) and two future OA scenarios (7.85 and 7.75). Total bioerosion (buoyant weight), chemical bioerosion, and mechanical bioerosion rates were measured to evaluate trends related to seawater pH. We identified a parabolic relationship between OA and sponge bioerosion, with the highest rates measured in the moderate OA treatment (7.85 pH) and decreasing under the more extreme OA treatment (7.75 pH). This suggests that sponges may become physiologically impaired under prolonged exposure to extreme OA, resulting in diminished bioerosion potential. These data reveal that carbonate dissolution is likely to increase in the upcoming decades as a result of OA-enhanced sponge bioerosion, but that the long-term persistence of reef habitat may benefit from reduced sponge bioerosion under late century OA scenarios.