title: Ocean acidification alters the material properties of Mytilus edulis shells.
abstract: Ocean acidification (OA) and the resultant changing carbonate saturation states is threatening the formation of calcium carbonate shells and exoskeletons of marine organisms. The production of biominerals in such organisms relies on the availability of carbonate and the ability of the organism to biomineralize in changing environments. To understand how biomineralizers will respond to OA the common blue mussel, Mytilus edulis, was cultured at projected levels of pCO2 (380, 550, 750, 1000 µatm) and increased temperatures (ambient, ambient plus 2°C). Nanoindentation (a single mussel shell) and microhardness testing were used to assess the material properties of the shells. Young's modulus (E), hardness (H) and toughness (KIC) were measured in mussel shells grown in multiple stressor conditions. OA caused mussels to produce shell calcite that is stiffer (higher modulus of elasticity) and harder than shells grown in control conditions. The outer shell (calcite) is more brittle in OA conditions while the inner shell (aragonite) is softer and less stiff in shells grown under OA conditions. Combining increasing ocean pCO2 and temperatures as projected for future global ocean appears to reduce the impact of increasing pCO2 on the material properties of the mussel shell. OA may cause changes in shell material properties that could prove problematic under predation scenarios for the mussels; however, this may be partially mitigated by increasing temperature.
authors.affiliation: School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK susan.fitzer@glasgow.ac.uk.
authors.forename: Susan C
authors.identifier: http://orcid.org/0000-0003-3556-7624
authors.initials: SC
authors.lastname: Fitzer
authors.affiliation: School of Engineering, University of the West of Scotland, Paisley PA1 2BE, UK.
authors.forename: Wenzhong
authors.identifier: http://orcid.org/0000-0002-2669-9177
authors.initials: W
authors.lastname: Zhu
authors.affiliation: School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: K Elizabeth
authors.identifier: http://orcid.org/0000-0003-2257-0218
authors.initials: KE
authors.lastname: Tanner
authors.affiliation: School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Vernon R
authors.identifier: http://orcid.org/0000-0002-8682-5200
authors.initials: VR
authors.lastname: Phoenix
authors.affiliation: School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Nicholas A
authors.identifier: http://orcid.org/0000-0003-3434-0807
authors.initials: NA
authors.lastname: Kamenos
authors.affiliation: School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Maggie
authors.identifier: http://orcid.org/0000-0003-0145-1180
authors.initials: M
authors.lastname: Cusack
mesh_terms: D060105:Animal Shells / Q000378:metabolism*; D000818:Animals; D002113:Calcification, Physiologic; D002245:Carbon Dioxide; D006863:Hydrogen-Ion Concentration; D049880:Mytilus edulis / Q000378:metabolism*; D009792:Oceans and Seas
chemical_list: D002245:Carbon Dioxide
keywords: CO2; biomineralization; multiple stressors; mussels; ocean acidification; temperature