No abstract

Rising atmospheric carbon dioxide (CO 2 ) conditions are driving unprecedented changes in seawater chemistry, resulting in reduced pH and carbonate ion concentrations in the Earth's oceans. This ocean acidification has negative but variable impacts on individual performance in many marine species. However, little is known about the adaptive capacity of species to respond to an acidified ocean, and, as a result, predictions regarding future ecosystem responses remain incomplete. Here we demonstrate that ocean acidification generates striking patterns of genome-wide selection in purple sea urchins (Strongylocentrotus purpuratus) cultured under different CO 2 levels. We examined genetic change at 19,493 loci in larvae from seven adult populations cultured under realistic future CO 2 levels. Although larval development and morphology showed little response to elevated CO 2 , we found substantial allelic change in 40 functional classes of proteins involving hundreds of loci. Pronounced genetic changes, including excess amino acid replacements, were detected in all populations and occurred in genes for biomineralization, lipid metabolism, and ion homeostasis-gene classes that build skeletons and interact in pH regulation. Such genetic change represents a neglected and important impact of ocean acidification that may influence populations that show few outward signs of response to acidification. Our results demonstrate the capacity for rapid evolution in the face of ocean acidification and show that standing genetic variation could be a reservoir of resilience to climate change in this coastal upwelling ecosystem. However, effective response to strong natural selection demands large population sizes and may be limited in species impacted by other environmental stressors.experimental evolution | population genomics | RNA sequencing | adaptation | environmental mosaic A ccelerating increases in ocean CO 2 concentrations and accompanying declines in pH are expected this century (1, 2), particularly in the California Current System (3). The negative impacts of ocean acidification have been seen in a broad range of species (4-8) and are predicted to lead to future populations of individuals with low growth, reproduction, or survival. However, the capacity of marine populations to adapt to these changes is unknown (9, 10), and, as a result, there may be circumstances in which natural selection could result in populations of individuals with better-than-expected fitness under acidified conditions. Until recently, the tools to scan for standing genetic variation with adaptive potential in the face of climate change have not been broadly available. Here we combine sequencing across the transcriptome of the purple sea urchin Strongylocentrotus purpuratus, growth measurements under experimental acidification, and tests of frequency shifts in 19,493 polymorphisms during development. We detect the widespread occurrence of genetic variation to tolerate ocean acidification.Rapid evolution in changing environments is likely to depend ...

International audience[1] Thirteen laboratories from the USA and Europe participated in an intercomparison study of Mg/Ca and Sr/Ca measurements in foraminifera. The study included five planktonic species from surface sediments from different geographical regions and water depths. Each of the laboratories followed their own cleaning and analytical procedures and had no specific information about the samples. Analysis of solutions of known Mg/Ca and Sr/Ca ratios showed that the intralaboratory instrumental precision is better than 0.5% for both Mg/Ca and Sr/Ca measurements, regardless whether ICP-OES or ICP-MS is used. The interlaboratory precision on the analysis of standard solutions was about 1.5% and 0.9% for Mg/Ca and Sr/Ca measurements, respectively. These are equivalent to Mg/Ca-based temperature repeatability and reproducibility on the analysis of solutions of +/- 0.2 degreesC and +/- 0.5 degreesC, respectively. The analysis of foraminifera suggests an interlaboratory variance of about +/-8% (%RSD) for Mg/Ca measurements, which translates to reproducibility of about +/- 2 - 3 degreesC. The relatively large range in the reproducibility of foraminiferal analysis is primarily due to relatively poor intralaboratory repeatability (about +/- 1 - 2 degreesC) and a bias (about 1 degreesC) due to the application of different cleaning methods by different laboratories. Improving the consistency of cleaning methods among laboratories will, therefore, likely lead to better reproducibility. Even more importantly, the results of this study highlight the need for standards calibration among laboratories as a first step toward improving interlaboratory compatibility

No abstract

SUMMARYAnthropogenic CO 2 is reducing the pH and altering the carbonate chemistry of seawater, with repercussions for marine organisms and ecosystems. Current research suggests that calcification will decrease in many species, but compelling evidence of impaired functional performance of calcium carbonate structures is sparse, particularly in key species. Here we demonstrate that ocean acidification markedly degrades the mechanical integrity of larval shells in the mussel Mytilus californianus, a critical community member on rocky shores throughout the northeastern Pacific. Larvae cultured in seawater containing CO 2 concentrations expected by the year 2100 (540 or 970ppm) precipitated weaker, thinner and smaller shells than individuals raised under presentday seawater conditions (380ppm), and also exhibited lower tissue mass. Under a scenario where mussel larvae exposed to different CO 2 levels develop at similar rates, these trends suggest a suite of potential consequences, including an exacerbated vulnerability of new settlers to crushing and drilling attacks by predators; poorer larval condition, causing increased energetic stress during metamorphosis; and greater risks from desiccation at low tide due to shifts in shell area to body mass ratios. Under an alternative scenario where responses derive exclusively from slowed development, with impacted individuals reaching identical milestones in shell strength and size by settlement, a lengthened larval phase could increase exposure to high planktonic mortality rates. In either case, because early life stages operate as population bottlenecks, driving general patterns of distribution and abundance, the ecological success of this vital species may be tied to how ocean acidification proceeds in coming decades.Key words: biomineralization, early survivorship, environmental change, form and function, shell properties. THE JOURNAL OF EXPERIMENTAL BIOLOGY Impaired larval shell integrityPotential tradeoffs among calcification and other physiological responses are likewise poorly understood (Hofmann and Todgham, 2010). Most marine calcifiers can increase fluid pH and carbonate ion concentration at the site of crystal nucleation, which enables synthesis of shells and/or skeletons even when external seawater parameters are thermodynamically unfavorable for the formation of CaCO 3 (Cohen and Holcomb, 2009). Maintenance of local conditions that differ from those of surrounding waters, however, often depends on active ion transport that is energetically costly (Palmer, 1992; Cohen and Holcomb, 2009). Whether OA-induced energetic expenditures require that organisms differentially prioritize certain physiological processes is largely unknown (Widdicomb and Spicer, 2008). In shell-forming species, for instance, it is unclear whether decreased growth arises from somatic resources being redirected to fortify the shell or as a direct consequence of acidified seawater. If OA reduces both growth and shell integrity, it is uncertain which might be degraded more strongly.Such que...