Biochemical adaptation to ocean acidification

Abstract

The change in oceanic carbonate chemistry due to increased atmospheric P CO2 has caused pH to decline in marine surface waters, a phenomenon known as ocean acidification (OA). The effects of OA on organisms have been shown to be widespread among diverse taxa from a wide range of habitats. The majority of studies of organismal response to OA are in short-term exposures to future levels of P CO2 . From such studies, much information has been gathered on plastic responses organisms may make in the future that are beneficial or harmful to fitness. Relatively few studies have examined whether organisms can adapt to negative-fitness consequences of plastic responses to OA. We outline major approaches that have been used to study the adaptive potential for organisms to OA, which include comparative studies and experimental evolution. Organisms that inhabit a range of pH environments (e.g. pH gradients at volcanic CO 2 seeps or in upwelling zones) have great potential for studies that identify adaptive shifts that have occurred through evolution. Comparative studies have advanced our understanding of adaptation to OA by linking whole-organism responses with cellular mechanisms. Such optimization of function provides a link between genetic variation and adaptive evolution in tuning optimal function of rate-limiting cellular processes in different pH conditions. For example, in experimental evolution studies of organisms with short generation times (e.g. phytoplankton), hundreds of generations of growth under future conditions has resulted in fixed differences in gene expression related to acid-base regulation. However, biochemical mechanisms for adaptive responses to OA have yet to be fully characterized, and are likely to be more complex than simply changes in gene expression or protein modification. Finally, we present a hypothesis regarding an unexplored area for biochemical adaptation to ocean acidification. In this hypothesis, proteins and membranes exposed to the external environment, such as epithelial tissues, may be susceptible to changes in external pH. Such biochemical systems could be adapted to a reduced pH environment by adjustment of weak bonds in an analogous fashion to biochemical adaptation to temperature. Whether such biochemical adaptation to OA exists remains to be discovered.

Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

“…The prominent changes in temperature and carbon fluxes almost assuredly caused large variations in seawater pH and carbonate ion concentration (CO 2− 3 ; Dickens et al, 1997;Zachos et al, 2005;Kump et al, 2009;Zeebe et al, 2009;LeonRodriguez and Dickens, 2010;Hönisch et al, 2012;, although the response should depend on location and carbon fluxes involved (Dickens, 2000;Zeebe and Westbroek, 2003;Komar et al, 2013). Such changes might also affect the ability of living organisms to calcify (Riebesell et al, 2000(Riebesell et al, , 2008Kleypas et al, 2006;Iglesias-Rodriguez et al, 2008;Stillman and Paganini, 2015), which might impact the fossil record (Agnini et al, 2006;Raffi and De Bernardi, 2008;Erba et al, 2010;Hönisch et al, 2012).…”

Interactive effects of seawater acidification and elevated temperature on biomineralization and amino acid metabolism in the musselMytilus edulis

“…Global seawater surface pH is projected to drop a further 0.3-0.4 units by the end of this century, with seawater warming of 1-4°C (Bates et al, 2008;Doney et al, 2012). Seawater acidification and warming have negative impacts on the larval development, growth, reproduction, biomineralization, and physiological and biochemical performance of some marine organisms, especially marine calcifiers, by disturbing ion and acid-base equilibrium, energy budgets and calcium carbonate (CaCO 3 ) saturation state (CeballosOsuna et al, 2013;Gazeau et al, 2013;Paganini et al, 2014;Pimentel et al, 2014;Rosa et al, 2014;Schlegel et al, 2015;Stillman and Paganini, 2015;Turner et al, 2015;Wittmann and Portner, 2013;Yao and Somero, 2014).…”

Dimethylsulfide (DMS) production in polar oceans may be resilient to ocean acidification

“…Nevertheless, our approach can provide insight into the physiological response of a variety of 130 polar surface ocean communities, as well as their potential adaptive capacity to future OA when compared between environments that differ in carbonate chemistry (Stillman and Paganini 2015), alongside the implications this may have for DMS production.…”