The metabolic response of thecosome pteropods from the North Atlantic and North Pacific oceans to high CO<sub>2</sub> and low O<sub>2</sub> Academic Article uri icon

abstract

  • <p><strong>Abstract.</strong> As anthropogenic activities directly and indirectly increase carbon dioxide (CO<sub>2</sub>) and decrease oxygen (O<sub>2</sub>) concentrations in the ocean system, it becomes important to understand how different populations of marine animals will respond. Water that is naturally low in pH, with a high concentration of carbon dioxide (hypercapnia) and a low concentration of oxygen, occurs at shallow depths (200–500<span class="thinspace"></span>m) in the North Pacific Ocean, whereas similar conditions are absent throughout the upper water column in the North Atlantic. This contrasting hydrography provides a natural experiment to explore whether differences in environment cause populations of cosmopolitan pelagic calcifiers, specifically the aragonitic-shelled pteropods, to have a different physiological response when exposed to hypercapnia and low O<sub>2</sub>. Using closed-chamber end-point respiration experiments, eight species of pteropods from the two ocean basins were exposed to high CO<sub>2</sub> (???<span class="thinspace"></span>800<span class="thinspace"></span>µatm) while six species were also exposed to moderately low O<sub>2</sub> (48<span class="thinspace"></span>% saturated, or ???<span class="thinspace"></span>130<span class="thinspace"></span>µmol<span class="thinspace"></span>kg<sup>?1</sup>) and a combined treatment of low O<sub>2</sub>/high CO<sub>2</sub>. None of the species tested showed a change in metabolic rate in response to high CO<sub>2</sub> alone. Of those species tested for an effect of O<sub>2</sub>, only <i>Limacina retroversa</i> from the Atlantic showed a response to the combined treatment, resulting in a reduction in metabolic rate. Our results suggest that pteropods have mechanisms for coping with short-term CO<sub>2</sub> exposure and that there can be interactive effects between stressors on the physiology of these open ocean organisms that correlate with natural exposure to low O<sub>2</sub> and high CO<sub>2</sub>. These are considerations that should be taken into account in projections of organismal sensitivity to future ocean conditions.</p>

publication date

  • November 17, 2016