Impact of Ocean Acidification on Energy Metabolism of Oyster, Crassostrea gigas—Changes in Metabolic Pathways and Thermal Response

Abstract

Climate change with increasing temperature and ocean acidification (OA) poses risks for marine ecosystems. According to Pörtner and Farrell [1], synergistic effects of elevated temperature and CO2-induced OA on energy metabolism will narrow the thermal tolerance window of marine ectothermal animals. To test this hypothesis, we investigated the effect of an acute temperature rise on energy metabolism of the oyster, Crassostrea gigas chronically exposed to elevated CO2 levels (partial pressure of CO2 in the seawater ~0.15 kPa, seawater pH ~ 7.7). Within one month of incubation at elevated Pco2 and 15 °C hemolymph pH fell (pHe = 7.1 ± 0.2 (CO2-group) vs. 7.6 ± 0.1 (control)) and Peco2 values in hemolymph increased (0.5 ± 0.2 kPa (CO2-group) vs. 0.2 ± 0.04 kPa (control)). Slightly but significantly elevated bicarbonate concentrations in the hemolymph of CO2-incubated oysters ([HCO− 3]e = 1.8 ± 0.3 mM (CO2-group) vs. 1.3 ± 0.1 mM (control)) indicate only minimal regulation of extracellular acid-base status. At the acclimation temperature of 15 °C the OA-induced decrease in pHe did not lead to metabolic depression in oysters as standard metabolism rates (SMR) of CO2-exposed oysters were similar to controls. Upon acute warming SMR rose in both groups, but displayed a stronger increase in the CO2-incubated group. Investigation in isolated gill cells revealed a similar temperaturedependence of respiration between groups. Furthermore, the fraction of cellular energy demand for ion regulation via Na+/K+-ATPase was not affected by chronic hypercapnia or temperature. Metabolic profiling using 1H-NMR spectroscopy revealed substantial changes in some tissues following OA exposure at 15 °C. In mantle tissue alanine and ATP levels decreased significantly whereas an increase in succinate levels was observed in gill tissue. These findings suggest shifts in metabolic pathways following OA-exposure. Our study confirms that OA affects energy metabolism in oysters and suggests that climate change may affect populations of sessile coastal invertebrates such as mollusks.

Effects of low-pH stress on shell traits of the dove snail, <i>Anachis misera</i>, inhabiting shallow-vent environments off Kueishan Islet, Taiwan

“…Similar results have been obtained for other calcifying organisms, e.g., the reduction in shell growth of the oysters Crassostrea gigas (Lannig et al, 2010) and Crassostrea virginica (Beniash et al, 2010), of the larvae of the Mediterranean pteropods Cavolinia inflexa (Comeau et al, 2010), and of the mussels Mytilus edulis (Gazeau et al, 2010) and Mytilus californianus (Gaylord et al, 2011). Along a gradient of pH (5.…”

Effects of ocean acidification on immune responses of the Pacific oyster Crassostrea gigas

“…For example, OA was found to impact survival, development, physiology and growth of many marine mollusks [32]. Furthermore, OA exposure can also disturb the energy metabolism and regulation which might affect immune function in bivalves [14,18]. Recently, it has been found that OA stress has the potential to promote pathogen development and survival, disease transmission and host susceptibility [33].…”

“…Moreover, OA stress has also been found to affect many physiological processes, such as calcification [13], energy metabolism [14] and behavior [15,16] of calcifying organisms. However, there is a lack of studies on the effects of OA on other vital processes of marine organisms such as immune and stress responses [17].…”

Impacts of ocean acidification on marine shelled molluscs

“…4) while four experiments concluded on an increase in their SMR during exposure to elevated CO 2 (Lannig et al 2010;Cummings et al 2011;Parker et al 2012), suggesting an ability to at least partially compensate for the increased energy costs of acidosis (Wicks and Roberts 2012). In the mussel M. edulis, for example, exposure to elevated CO 2 of 1,120 latm (-0.3 pH unit) for 60 days led to a significant increase in SMR .…”