Seawater carbonate chemistry and gastropod shell composition

• Main Authors: Barclay, Kristina M, Gingras, Murray K, Packer, Stephen T, Leighton, Lindsey R
• Format: Dataset
• Language: English
• Published: PANGAEA 2020
• Subjects: Alkalinity; total; standard deviation; Animalia; Aragonite; Aragonite saturation state; Benthic animals; Benthos; Bicarbonate ion; Bodega_Marine_Reserve; Bottles or small containers/Aquaria (<20 L); Calcification/Dissolution; Calcite; Calcite/Aragonite ratio; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Calculated using seacarb after Orr et al. (2018); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Comment; EXP; Experiment; Experiment duration; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Fugacity of carbon dioxide in seawater; Greyscale value; Identification; Laboratory experiment; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.925655; https://doi.org/10.1594/PANGAEA.925655

Organisms, such as molluscs, that produce their hard parts from calcium carbonate are expected to show increased difficulties growing and maintaining their skeletons under ocean acidification (OA). Any loss of shell integrity increases vulnerability, as shells provide protection against predation, desiccation, and disease. Not all species show the same responses to OA, which may be due to the composition and microstructural arrangement of their shells. We explore the role of shell composition and microstructure in resisting dissolution caused by decreases in seawater pH using a combination of microCT scans, XRD analysis, and SEM imaging. Two gastropods with different shell compositions and microstructure, Tegula funebralis and Nucella ostrina, were exposed to simulated ocean acidification conditions for six months. Both species showed signs of dissolution on the exterior of their shells, but changes in density were significantly more pronounced in T. funebralis. XRD analysis indicated that the exterior layer of both shell types was made of calcite. T. funebralis may be more prone to dissolution because their outer fibrous calcite layer has more crystal edges and faces exposed, potentially increasing the surface area on which dissolution can occur. These results support a previous study where T. funebralis showed significant decreases in both shell growth and strength, but N. ostrina only showed slight reductions in shell strength, and unaffected growth. We suggest that microstructural arrangement of shell layers in molluscs, more so than their composition alone, is critical for determining the vulnerability of mollusc shells to OA.