Seawater carbonate chemistry and adhesion and shell formation of the Barnacle Amphibalanus amphitrite

• Main Authors: Nardone, Jessica A, Patel, Shrey, Siegel, Kyle R, Tedesco, Dana, McNicholl, Conall G, O'Malley, Jessica, Herrick, Jack, Metzler, Rebecca A, Orihuela, Beatriz, Rittschof, Daniel, Dickinson, Gary H
• Format: Dataset
• Language: English
• Published: PANGAEA 2018
• Subjects: Adhesive strength; standard error; Alkalinity; total; standard deviation; Amphibalanus amphitrite; Animalia; Aragonite saturation state; Area; Arthropoda; Atomic disorder; Benthic animals; Benthos; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcite crystal area; Calcite saturation state; Calcium; Calculated using CO2calc; 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; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.922978; https://doi.org/10.1594/PANGAEA.922978

Barnacles are dominant members of marine intertidal communities. Their success depends on firm attachment provided by their proteinaceous adhesive and protection imparted by their calcified shell plates. Little is known about how variations in the environment affect adhesion and shell formation processes in barnacles. Increased levels of atmospheric CO2 have led to a reduction in the pH of ocean waters (i.e., ocean acidification), a trend that is expected to continue into the future. Here, we assessed if a reduction in seawater pH, at levels predicted within the next 200 years, would alter physiology, adhesion, and shell formation in the cosmopolitan barnacle Amphibalanus (=Balanus) amphitrite. Juvenile barnacles, settled on silicone substrates, were exposed to one of three static levels of pHT, 8.01, 7.78, or 7.50, for 13 weeks. We found that barnacles were robust to reduced pH, with no effect of pH on physiological metrics (mortality, tissue mass, and presence of eggs). Likewise, adhesive properties (adhesion strength and adhesive plaque gross morphology) were not affected by reduced pH. Shell formation, however, was affected by seawater pH. Shell mass and base plate area were higher in barnacles exposed to reduced pH; barnacles grown at pHT 8.01 exhibited approximately 30% lower shell mass and 20% smaller base plate area as compared to those at pHT 7.50 or 7.78. Enhanced growth at reduced pH appears to be driven by the increased size of the calcite crystals that comprise the shell. Despite enhanced growth, mechanical properties of the base plate (but not the parietal plates) were compromised at the lowest pH level. Barnacle base plates at pHT 7.50 broke more easily and crack propagation, measured through microhardness testing, was significantly affected by seawater pH. Other shell metrics (plate thickness, relative crystallinity, and atomic disorder) were not affected by seawater pH. Hence, a reduction in pH resulted in larger barnacles but with base plates that would crack more readily. It is yet to be ...