Effect of elevated pCO2 on metabolic responses of porcelain crab (Petrolisthes cinctipes) Larvae exposed to subsequent salinity stress

Abstract

Future climate change is predicted to alter the physical characteristics of oceans and estuaries, including pH, temperature, oxygen, and salinity. Investigating how species react to the influence of such multiple stressors is crucial for assessing how future environmental change will alter marine ecosystems. The timing of multiple stressors can also be important, since in some cases stressors arise simultaneously, while in others they occur in rapid succession. In this study, we investigated the effects of elevated pCO2 on oxygen consumption by larvae of the intertidal porcelain crab Petrolisthes cinctipes when exposed to subsequent salinity stress. Such an exposure mimics how larvae under future acidified conditions will likely experience sudden runoff events such as those that occur seasonally along portions of the west coast of the U.S. and in other temperate systems, or how larvae encounter hypersaline waters when crossing density gradients via directed swimming. We raised larvae in the laboratory under ambient and predicted future pCO2 levels (385 and 1000 µatm) for 10 days, and then moved them to seawater at ambient pCO2 but with decreased, ambient, or elevated salinity, to monitor their respiration. While larvae raised under elevated pCO2 or exposed to stressful salinity conditions alone did not exhibit higher respiration rates than larvae held in ambient conditions, larvae exposed to elevated pCO2 followed by stressful salinity conditions consumed more oxygen. These results show that even when multiple stressors act sequentially rather than simultaneously, they can retain their capacity to detrimentally affect organisms.

Figure 1. Larval oxygen consumption through time.

Dissolved oxygen (mean total oxygen less background bacterial consumption rates, ± S.E.) during respirometry trials under ambient or dual-stressor conditions. Horizontal dashed line shows the lower limit of data analyzed in this study; data for oxygen levels under 5 mgL⁻¹ are presented for completeness.

Figure 2. Multi-stressor effects on larvae.

Oxygen consumption (mean ± S.E.) by larvae subjected to salinity stress, CO₂ stress, both stressors, and ambient conditions; bars connected by the same letter are not significantly different. Larvae subjected to ambient conditions consumed significantly less oxygen than larvae subjected to both salinity and CO₂ stress (p = 0.0149). There were no differences in oxygen consumption between larvae raised at ambient conditions and larvae subjected to a single stressor.

Figure 3. Respiration of larvae under stressful and ambient conditions.

Oxygen consumption (mean ± S.E.) at stressful and ambient salinities by larvae raised under two pCO₂ treatments. Overall, larvae consumed significantly less oxygen at ambient (34) salinity (open squares) than at depressed or elevated (22 or 40) salinities (filled squares, p = 0.0038), though there was no difference in oxygen consumption between pCO₂ treatments (p = 0.1626).