Ocean acidification bends the mermaid's wineglass

Abstract

Ocean acidification lowers the saturation state of calcium carbonate, decreasing net calcification and compromising the skeletons of organisms such as corals, molluscs and algae. These calcified structures can protect organisms from predation and improve access to light, nutrients and dispersive currents. While some species (such as urchins, corals and mussels) survive with decreased calcification, they can suffer from inferior mechanical performance. Here, we used cantilever beam theory to test the hypothesis that decreased calcification would impair the mechanical performance of the green alga Acetabularia acetabulum along a CO 2 gradient created by volcanic seeps off Vulcano, Italy. Calcification and mechanical properties declined as calcium carbonate saturation fell; algae at 2283 matm CO 2 were 32% less calcified, 40% less stiff and 40% droopier. Moreover, calcification was not a linear proxy for mechanical performance; stem stiffness decreased exponentially with reduced calcification. Although calcifying organisms can tolerate high CO 2 conditions, even subtle changes in calcification can cause dramatic changes in skeletal performance, which may in turn affect key biotic and abiotic interactions.

Acclimation of bloom‐forming and perennial seaweeds to elevated pCO2 conserved across levels of environmental complexity

“…Our results stand in contrast to studies carried out in naturally CO 2 rich systems, where it is often nonbloom-forming species traditionally grouped within the Phaeophyta that perform best (Enochs et al, 2015;Johnson et al, 2012;Linares et al, 2015;Porzio et al, 2011). Similar studies that find heterokont algae to cope best at high pCO 2 levels, with only some green seaweeds (such as Ulva) surviving the long-term effects of ocean acidification (Newcomb, Milazzo, Hall-Spencer, & Carrington, 2015).…”

Effects of ocean acidification on the shells of four Mediterranean gastropod species near a CO2 seep

“…Much of this decline in biodiversity is due to reductions in the presence of calcifying marine organisms including scleractinian corals, mollusks and echinoderms (Inoue et al, 2013;Fabricius et al, 2014;Garilli et al, 2015). Species that do survive under acidified conditions may become more vulnerable to predation due to weakened shells/skeletons and are often smaller due to dissolution or physiological stress (Rodolfo-Metalpa et al, 2015;Langer et al, 2014;Collard et al, 2016;Newcomb et al, 2015;Harvey et al, 2016).…”

Sea HareAplysia punctata(Mollusca: Gastropoda) Can Maintain Shell Calcification under Extreme Ocean Acidification

“…Compromised structural integrity under lower pH has also been shown in marine algae, including at a site of "natural OA," an area of volcanic outgassing of CO 2 that is thought to closely mimic future OA conditions (Newcomb et al, 2015). Studies on the invertebrates in this and similar "natural OA" sites show much decreased structural integrity of calcified parts (Rodolfo-Metalpa et al, 2011), with consequences for survival and community dynamics (HallSpencer et al, 2008;Kroeker et al, 2011).…”