Calcification, growth and mortality of juvenile clams Ruditapes decussatus under increased pCO2 and reduced pH: Variable responses to ocean acidification at local scales?

• Published in: Journal of experimental marine biology and ecology 2011-01, Vol.396 (2), p.177-184
• Main Authors: Range, P., Chícharo, M.A., Ben-Hamadou, R., Piló, D., Matias, D., Joaquim, S., Oliveira, A.P., Chícharo, L.
• Format: Article
• Language: English
• Subjects: acidification; alkalinity; Animal and plant ecology; animal growth; Animal, plant and microbial ecology; biodiversity; Biological and medical sciences; Bivalves; calcification; Calcium carbonate; Carbon dioxide; clams; Climate change; Fundamental and applied biological sciences. Psychology; Invertebrates; Marine; Mollusca; Physiology; Ria Formosa; Ruditapes decussatus; Sea water ecosystems; seawater; spawning; survival rate; Synecology
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/j.jembe.2010.10.020

We investigated the effects of ocean acidification on juvenile clams Ruditapes decussatus (average shell length 10.24mm) in a controlled CO2 perturbation experiment. The carbonate chemistry of seawater was manipulated by diffusing pure CO2, to attain two reduced pH levels (by −0.4 and −0.7 pH units), which were compared to unmanipulated seawater. After 75days we found no differences among pH treatments in terms of net calcification, size or weight of the clams. The naturally elevated total alkalinity of local seawater probably contributed to buffer the effects of increased pCO2 and reduced pH. Marine organisms may, therefore, show diverse responses to ocean acidification at local scales, particularly in coastal, estuarine and transitional waters, where the physical–chemical characteristics of seawater are most variable. Mortality was significantly reduced in the acidified treatments. This trend was probably related to the occurrence of spontaneous spawning events in the control and intermediate acidification treatments. Spawning, which was unexpected due to the small size of the clams, was not observed for the pH −0.7 treatment, suggesting that the increased survival under acidified conditions may have been associated with a delay in the reproductive cycle of the clams. Future research about the impacts of ocean acidification on marine biodiversity should be extended to other types of biological and ecological processes, apart from biological calcification. ►Net calcification and growth of the clams were independent of the pH treatments. ►Elevated total alkalinity of local seawater buffered the effects of reduced pH. ►Biological responses to OA may be variable at local scales. ►Acidified treatments reduced mortalities of the clams. ►Reduced mortality was associated with a delay in the reproductive cycle.