Seawater acidification induced immune function changes of haemocytes in Mytilus edulis: a comparative study of CO2 and HCl enrichment

Abstract

The present study was performed to evaluate the effects of CO2− or HCl-induced seawater acidification (pH 7.7 or 7.1; control: pH 8.1) on haemocytes of Mytilus edulis, and the changes in the structure and immune function were investigated during a 21-day experiment. The results demonstrated that seawater acidification had little effect on the cellular mortality and granulocyte proportion but damaged the granulocyte ultrastructure. Phagocytosis of haemocytes was also significantly inhibited in a clearly concentration-dependent manner, demonstrating that the immune function was affected. Moreover, ROS production was significantly induced in both CO2 and HCl treatments, and four antioxidant components, GSH, GST, GR and GPx, had active responses to the acidification stress. Comparatively, CO2 had more severe destructive effects on haemocytes than HCl at the same pH level, indicating that CO2 stressed cells in other ways beyond the increasing H+ concentration. One possible explanation was that seawater acidification induced ROS overproduction, which damaged the ultrastructure of haemocytes and decreased phagocytosis.

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).…”

“…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). However, the protective response of the antioxidant system (SOD, CAT, several peroxiredoxins) by scavenging excess radicals, can be varied under different situations.…”

“…For the THC, only a mild trend was observed as only one replicate in pH 7.6 had significantly lower THC than one replicate on pH 8.0 (Figure 4). A decline in THC was also noted in Norway lobsters (Hernroth et al, 2012), Blue mussels (Sun et al, 2017), Blood clams (Liu et al, 2016), common starfish (Hernroth et al, 2011) and American lobsters (Harrington and Hamlin, 2019) exposed to low pH. A significant decrease of hemocyte numbers was observed in Pacific white shrimps exposed to pH 7.5 for 15 days compared to pH 8.0 (Pan et al, 2005) and the same species exposed to pH 6.5 for 120 h exhibited a significant decrease in THC as compared to shrimps raised at pH 8.2 (Li and Chen, 2008).…”

“…While the main focus of the early work was on calcification, immune defense and energy budget appeared to play a key role in species response to OA. Immune suppression under OA was observed in many invertebrate species including Norway lobsters (Hernroth et al, 2012), common starfish (Hernroth et al, 2011), blue mussels (Ellis et al, 2015;Sun et al, 2017), blood clams (Liu et al, 2016) and Pacific oysters (Cao et al, 2018). However, recent studies showed enhanced immune response in east pacific red octopus (Culler-Juarez and Onthank, 2021) and in Chinese mitten crabs (Luo et al, 2021) exposed to OA.…”

The Bloom-Forming Dinoflagellate Karenia mikimotoi Adopts Different Growth Modes When Exposed to Short or Long Period of Seawater Acidification

“…Two level of acidification were applied, namely 1000 ppmv (pH 7.8; the prediction of atmospheric CO 2 level in 2100) and 2000 ppmv (pH 7.5; the prediction of atmospheric CO 2 level in 2300) based on our previous studies [ 38 , 72 ]. p CO 2 of 390 ppmv (pH 8.1; ambient seawater pH) was used as the control.…”