Specific dynamic action of mussels exposed to TiO2 nanoparticles and seawater acidification.

Both nanoparticles (NPs) and ocean acidification (OA) pose threats to marine animals as well as marine ecosystems. The present study aims to evaluate the combined effects of NPs and OA on specific dynamic action (SDA) of mussels. The thick shell mussels Mytilus coruscus were exposed to two levels of pH (7.3 and 8.1) and three concentrations of TiO2 NPs (0, 2.5, and 10 mg L-1) for 14 days followed by a 7-day recovery period. The SDA parameters, including standard metabolic rate, peak metabolic rate, aerobic metabolic scope, SDA slope, time to peak, SDA duration and SDA, were measured. The results showed that TiO2 NPs and low pH significantly affected all parameters throughout the experiment. When the mussels were exposed to seawater acidification or TiO2 NPs conditions, standard metabolic rate, aerobic metabolic scope, SDA slope and SDA significantly decreased, whereas peak metabolic rate, time to peak and SDA duration significantly increased. In addition, interactive effects between TiO2 NPs and pH were observed in SDA parameters except time to peak and SDA. Therefore, the synergistic effect of TiO2 NPs and low pH can adversely affect the feeding metabolism of mussels.