Ocean acidification and hypoxia, both caused by anthropogenic activities, have showed deleterious impacts on marine animals. However, their combined effect on the mussel's defence to its predator has been poorly understood, which hinders us to understand the prey-predator interaction in marine environment. The thick shell mussel Mytilus coruscus and its predator, the Asian paddle crab Charybdis japonica were exposed to three pH levels (7.3, 7.7, 8.1) at two concentrations of dissolved oxygen (2.0 mg/L, 6.0 mg/L) seawater. The anti-predatory responses of mussels, in terms of byssus thread production were analysed after 72 h exposure. During the experiment, frequency of shedding stalks (mussels shed their byssal stalks to release themselves from attachment and allow locomotion) and number of byssus threads increased with time, were significantly reduced by hypoxia and low pH levels, and some interactions among time, predator, DO and pH were observed. As expected, the presence of the crab induced an anti-predator response in M. coruscus (significant increases in most tested parameters except the byssus thread length). Acidification and hypoxia significantly reduced byssus thread diamter at the end of the experiment, but not the byssus thread length. Cumulative byssus thread length and volume were significantly impaired by hypoxia and acidification. Our results highlight the significance of anti-predatory responses for adult mussel M. coruscus even under a stressful environment in which stress occurs through ocean acidification and hypoxia. By decreasing the strength of byssus attachment, the chance of being dislodged and consumed by crabs is likely increased. Our data suggest that there are changes in byssus production induced by hypoxia and acidification, which may affect predation rates on M. coruscus in the field.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2016) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2017-02-16.

Supplement to: Sui, Yanming; Hu, Menghong; Huang, Xizhi; Wang, Youji; Lu, Weiqun (2015): Anti-predatory responses of the thick shell mussel Mytilus coruscus exposed to seawater acidification and hypoxia. Marine Environmental Research, 109, 159-167