Defense Responses to Short-term Hypoxia and Seawater Acidification in the Thick Shell Mussel Mytilus coruscus

Abstract

The rising anthropogenic atmospheric CO2 results in the reduction of seawater pH, namely ocean acidification (OA). In East China Sea, the largest coastal hypoxic zone was observed in the world. This region is also strongly impacted by ocean acidification as receiving much nutrient from Changjiang and Qiantangjiang, and organisms can experience great short-term natural variability of DO and pH in this area. In order to evaluate the defense responses of marine mussels under this scenario, the thick shell mussel Mytilus coruscus were exposed to three pH/pCO2 levels (7.3/2800 μatm, 7.7/1020 μatm, 8.1/376 μatm) at two dissolved oxygen concentrations (DO, 2.0, 6.0 mg L−1) for 72 h. Results showed that byssus thread parameters, such as the number, diameter, attachment strength and plaque area were reduced by low DO, and shell-closing strength was significantly weaker under both hypoxia and low pH conditions. Expression patterns of genes related to mussel byssus protein (MBP) were affected by hypoxia. Generally, hypoxia reduced MBP1 and MBP7 expressions, but increased MBP13 expression. In conclusion, both hypoxia and low pH induced negative effects on mussel defense responses, with hypoxia being the main driver of change. In addition, significant interactive effects between pH and DO were observed on shell-closing strength. Therefore, the adverse effects induced by hypoxia on the defense of mussels may be aggravated by low pH in the natural environments.

Only as strong as the weakest link: structural analysis of the combined effects of elevated temperature and pCO2 on mussel attachment

“…(2013) and this study are due to effects on mussel physiology prior to thread deposition, similar to the altered expression of genes coding for foot proteins observed when pH decreases in M. coruscus by Zhao et al . (2017) and hypoxia as observed by Sui et al . (2017).…”

“…For example, elevated pCO 2 (>1200 μatm) lowers thread strength in Mytilus trossulus (O'Donnell et al ., 2013; George and Carrington, 2018), thread strength and production in Mytilus coruscus and Pinctada fucata (Zhao et al ., 2017; Li et al ., 2017; Kong et al ., 2019), and thread strength in Mytilus edulis (Kong et al ., 2019, but see Dickey et al ., 2018). However, there is little consensus when whole animal attachment is measured, with negative, neutral, and positive effects of elevated pCO 2 observed in Mytilus galloprovincialis , M. edulis, Xenostrobus securis , and M. coruscus , respectively (Babarro et al ., 2018; Clements et al ., 2018; Sui et al ., 2017). These same studies reported negative effects of elevated temperature on attachment in M. galloprovincialis and M. edulis , but not X. securis .…”

Growth and Mortality of Green Mussel Perna viridis Farmed at Ambong Bay and Marudu Bay, Sabah, Malaysia

“…This could be explained by the fact that bivalves are able to tolerate low dissolved oxygen (Wang et al, 2011). However, prolonged exposure of low dissolved oxygen may become a stress factor for mussels and weaken their defence response (Sui et al, 2017). The pH of nearshore waters fluctuates more than that of the open sea because of the biological activities that take place in the coastal areas (Cornwall et al, 2013).…”

Short-Term Exposure of Mytilus coruscus to Decreased pH and Salinity Change Impacts Immune Parameters of Their Haemocytes

“…OA also influences immune function (Wang et al, 2016 ), calcification (Zhang et al, 2007 ), and metabolism (Clark et al, 2013 ) in many other shellfish species. In addition, short-term pH decrease has been reported to affect defense responses (Sui et al, 2017b ), energy budget (Sui et al, 2016 ), and antioxidant response (Sui et al, 2017a ) of mussels. All together, these data suggest that OA will affect the healthy physiological activities of marine species (Lewis et al, 2016 ).…”