Experimental ocean acidification alters the allocation of metabolic energy

Abstract

Energy is required to maintain physiological homeostasis in response to environmental change. Although responses to environmental stressors frequently are assumed to involve high metabolic costs, the biochemical bases of actual energy demands are rarely quantified. We studied the impact of a near-future scenario of ocean acidification [800 μatm partial pressure of CO 2 (pCO 2 )] during the development and growth of an important model organism in developmental and environmental biology, the sea urchin Strongylocentrotus purpuratus. Size, metabolic rate, biochemical content, and gene expression were not different in larvae growing under control and seawater acidification treatments. Measurements limited to those levels of biological analysis did not reveal the biochemical mechanisms of response to ocean acidification that occurred at the cellular level. In vivo rates of protein synthesis and ion transport increased ∼50% under acidification. Importantly, the in vivo physiological increases in ion transport were not predicted from total enzyme activity or gene expression. Under acidification, the increased rates of protein synthesis and ion transport that were sustained in growing larvae collectively accounted for the majority of available ATP (84%). In contrast, embryos and prefeeding and unfed larvae in control treatments allocated on average only 40% of ATP to these same two processes. Understanding the biochemical strategies for accommodating increases in metabolic energy demand and their biological limitations can serve as a quantitative basis for assessing sublethal effects of global change. Variation in the ability to allocate ATP differentially among essential functions may be a key basis of resilience to ocean acidification and other compounding environmental stressors.ocean acidification | sea urchin | energetics | metabolic allocation | development

Urchins in a high CO2 world: partitioned effects of body-size, ocean warming and acidification on metabolic rate

“…Low pH has also been shown to alter ATP allocation, even when overall metabolic rate remains unaltered (Pan et al, 2015). How lowered seawater pH causes changes to metabolic rates in marine invertebrates is complex and often species-specific, depending on which part of the metabolic pathway is affected (Carter et al, 2013;Pan et al, 2015).…”

“…Low pH has also been shown to alter ATP allocation, even when overall metabolic rate remains unaltered (Pan et al, 2015). How lowered seawater pH causes changes to metabolic rates in marine invertebrates is complex and often species-specific, depending on which part of the metabolic pathway is affected (Carter et al, 2013;Pan et al, 2015). In sea urchins, the impacts of low pH may be minimal at the level of the organism, but cause a dramatic change to metabolic function at the cellular level (Pan et al, 2015) potentially compromising the energy available for biochemical functioning under environmental stress.…”

“…How lowered seawater pH causes changes to metabolic rates in marine invertebrates is complex and often species-specific, depending on which part of the metabolic pathway is affected (Carter et al, 2013;Pan et al, 2015). In sea urchins, the impacts of low pH may be minimal at the level of the organism, but cause a dramatic change to metabolic function at the cellular level (Pan et al, 2015) potentially compromising the energy available for biochemical functioning under environmental stress. A better understanding of the effects of acidification on the metabolic pathway is required to make better predictions as to how marine species will respond.…”

“…In larvae, two studies found OA caused increased R (Dorey et al, 2013;Stumpp et al, 2011). In one other, OA caused increased R in unfed larvae; in fed larvae there was no effect upon R but there were alterations to the allocation of metabolic energy (ATP) (Pan et al, 2015). Altered energy budgets unaccompanied by altered R have also been observed in adult sea urchins (Stumpp et al, 2012).…”

Using the critical salinity (S crit) concept to predict invasion potential of the anemone Diadumene lineata in the Baltic Sea

“…Cellular osmoregulation is an energy-dependent process. The physiological response to moderate abiotic stress often involves an increase in metabolic activity or a repartitioning of cellular energy allocation to compensate for the elevated energy demand induced by the stressor (Pan et al 2015). Severe stress may, however, exceed the organism's capacity to supply ATP from food or internal storages to sustain routine metabolism.…”