Impact of medium-term exposure to CO2 enriched seawater on the physiological functions of the velvet swimming crab Necora puber

Abstract

Ocean acidification (OA) is predicted to play a major role in shaping species biogeogra- phy and marine biodiversity over the next century. We tested the effect of medium-term exposure to OA (pH 8.00, 7.30 and 6.70 for 30 d) on acid-base balance in the decapod crab Necora puber—a spe- cies that is known to possess good extracellular buffering ability during short-term exposure to hypercapnic conditions. To determine if crabs undergo physiological trade-offs in order to buffer their haemolymph, we characterised a number of fundamental physiological functions, i.e. metabolic rate, tolerance to heat, carapace and chelae (Ca 2+ ) and (Mg 2+ ), haemolymph (Ca 2+ ) and (Mg 2+ ), and immune response in terms of lipid peroxidation. Necora puber was able to buffer changes to extra- cellular pH over 30 d exposure to hypercapnic water, with no evidence of net shell dissolution, thus demonstrating that HCO3 - is actively taken up from the surrounding water. In addition, tolerance to heat, carapace mineralization, and aspects of immune response were not affected by hypercapnic conditions. In contrast, whole-animal O2 uptake significantly decreased with hypercapnia, while significant increases in haemolymph (Ca 2+ ) and (Mg 2+ ) and chelae (Mg 2+ ) were observed with hyper- capnia. Our results confirm that most physiological functions in N. puber are resistant to low pH/ hypercapnia over a longer period than previously investigated, although such resistance comes at the expenses of metabolic rates, haemolymph chemistry and chelae mineralization.