Impact of Ocean Acidification on the Energy Metabolism and Antioxidant Responses of the Yesso Scallop (Patinopecten yessoensis)

Abstract

Ocean acidification (OA), which is caused by increasing levels of dissolved CO2 in the ocean, is a major threat to marine ecosystems. Multiple lines of scientific evidence show that marine bivalves, including scallops, are vulnerable to OA due to their poor capacities to regulate extracellular ions and acid-based status. However, the physiological mechanisms of scallops responding to OA are not well understood. In this study, we evaluated the effects of 45 days of exposure to OA (pH 7.5) on the energy metabolism and antioxidant capability of Yesso scallops. Some biochemical markers related to energy metabolism (e.g., content of glycogen and ATP, activity of ATPase, lactate dehydrogenase, glutamate oxaloacetate transaminase, and glutamate-pyruvate transaminase), antioxidant capacity (e.g., reactive oxygen species level, activity of superoxide dismutase, and catalase) and cellular damage (e.g., lipid peroxidation level) were measured. Our results demonstrate that the effects of the reduced pH (7.5) on scallops are varied in different tissues. The energy reserves are mainly accumulated in the adductor muscle and hepatopancreas. Yesso scallops exhibit energy modulation by increasing lactate dehydrogenase activities to stimulate anaerobic metabolism. The highly active Na+/K+-ATPase and massive ATP consumption in the mantle and gill indicate that a large amount of energy was allocated for the ion regulation process to maintain the acid-base balance in the reduced-pH environment. Moreover, the increase in the reactive oxygen species level and the superoxide dismutase and catalase activities in the gill and adductor muscle, indicate that oxidative stress was induced after long-term exposure to the reduced-pH environment. Our findings indicate that the effects of OA are tissue-specific, and physiological homeostasis could be modulated through different mechanisms for Yesso scallops.

Impacts of pH on the Fitness and Immune System of Pacific White Shrimp

“…Our results show that exposure to pH 7.6 increased superoxide production as compared to the two other pH treatments (Figure 5). This is consistent with the available literature, mostly on mollusks, showing that decreased pH can stimulate oxidative stress in the marine organism through increased ROS production (Tomanek et al, 2011;Wang et al, 2016;Sun et al, 2017;Cao et al, 2018;Liao et al, 2019). Enhanced production of ROS such as superoxide ions and hydrogen peroxide were observed under various environmental challenges in marine invertebrates (Liu and Chen, 2004;Hannam et al, 2010;Hernroth et al, 2012;Wang et al, 2016;Sun et al, 2017;Cao et al, 2018).…”

Correlation between intermediary metabolism,Hspgene expression, and oxidative stress-related proteins in long-term thermal-stressedMytilus galloprovincialis

“…During prolonged hypoxic exposure, however, anaerobic degradation of glycogen could be considered another major adaptive mechanism that contributes to longer survival during sustained environmental hypoxia (63,64,73,79). Several works reported that decreased pH alone or synergistically, either with increased temperature or with low oxygen tension, induces anti-oxidative response in marine bivalves (42,57,96), while Tomanek (99) and Sokolova (85) further discuss the possible mechanisms leading to mitochondrial ROS formation during exposure of mussels to elevated CO 2 and low pH i . The voluntary switch to anaerobiosis in bivalves may serve as a mechanism reducing ROS formation, thus resulting to longer survival (3,27).…”

The marine gastropodCrepidula fornicataremains resilient to ocean acidification across two life history stages

“…We also observed downregulation of genes associated with oxidation-reduction processes (Figures 4 & S3), which, in conjunction with downregulation of electron transport, may reflect a dampened immune system. The electron transport chain is a site that produces reactive oxygen species, which are an important internal defense mechanism, but which need to be controlled by antioxidant enzymes (Cao et al, 2018; Liao et al, 2018). Downregulation of genes associated with oxidation-reduction may deplete the availability of antioxidants to counteract reactive oxygen species, thereby overwhelming the antioxidant defense mechanisms.…”