Ocean Acidification Capacity Is Needed at All Levels to Develop a Multistakeholder Ocean Acidification Action Platform

<p>A central goal of climate science and policy is to establish and follow carbon emissions pathways towards a single metric of changes in the Earth system. Currently, this most often means restricting global mean surface warming to 1.5 and 2 °C, in line with the Paris Climate Agreement. However, anthropogenic emissions do not lead solely to increases in global mean temperature, but also cause other changes to the Earth system. This study aims to quantify carbon emission pathways that are consistent with additional climate targets, and explore the impact of applying these additional climate targets on the future carbon budget. Here, we consider ocean acidification, although eventually multiple additional climate targets could be considered. </p><p>Emission of carbon dioxide leads to ocean acidification, since the ocean is a significant carbon sink in the climate system, absorbing an estimated 16 to 30% of yearly anthropogenic carbon emissions (Friedlingstein et al., 2020). Increased ocean acidification threatens ocean biodiversity, specifically coral reef systems and calcifying organisms, with impacts up the food web. The effects of acidification extend towards human systems, in part due to the impact on fisheries: Narita et al. (2012) estimate that the loss of mollusk production alone due to acidification could cost 100 billion USD globally following a business-as-usual trajectory towards 2100.</p><p>Despite the far-reaching damage caused by ocean acidification, there has been little successful effort to explicitly address ocean acidification in climate policy apart from the Paris Agreement warming targets of 1.5 and 2°C (Harrould-Kolieb and Herr, 2012). Although these targets mitigate many elements of dangerous climate change, Schleussner et al. (2016) project that carbon emission pathways consistent with 1.5°C cause 90% of coral reef areas between 66°N and 66°S to be at risk of long-term degradation in all but a single model run.  </p><p>Calculating a future carbon budget based on a temperature goal alone is subject to significant uncertainty, largely due to uncertainties in response of the climate system to forcing and natural carbon sequestration. Here, results from a large observation-constrained model ensemble are presented for pathways that achieve multiple climate targets. The uncertainty in the resulting future carbon budget, compared to the budget for temperature-only targets, is discussed. A secondary aim is to establish a pair of mean ocean pH targets that are analogous with the Paris Agreement targets for global mean warming. </p><p>References </p><p>Friedlingstein P. et al., 2020, Earth System Science Data, DOI: 10.5194/essd-12-3269-2020</p><p>Narita, D. et al., 2012, Climate Change, DOI: 10.1007/s10584-011-0383-3</p><p>Harrould-Kolieb E.R. et al., 2012, Climate Policy, DOI: 10.1080/14693062.2012.620788</p><p>Schleussner C-F. et al., 2016, Earth System Dynamics, DOI: 10.1080/14693062.2012.620788</p>

Physiology, behaviour and inter-species interactions of jellyfish under changing ocean conditions

Anthropogenic carbon emissions are causing changes in seawater carbonate chemistry including a decline in the pH of the oceans. While its aftermath for calcifying microbes has been widely studied, the effect of ocean acidification (OA) on marine viruses and their microbial hosts is controversial, and even more in combination with another anthropogenic stressor, i.e., human-induced nutrient loads. In this study, two mesocosm acidification experiments with Mediterranean waters from different seasons revealed distinct effects of OA on viruses and viral-mediated prokaryotic mortality depending on the trophic state and the successional stage of the plankton community. In the winter bloom situation, low fluorescence viruses, the most abundant virus-like particle (VLP) subpopulation comprising mostly bacteriophages, were negatively affected by lowered pH with nutrient addition, while the bacterial host abundance was stimulated. High fluorescence viruses, containing cyanophages, were stimulated by OA regardless of the nutrient conditions, while cyanobacteria of the genus Synechococcus were negatively affected by OA. Moreover, the abundance of very high fluorescence viruses infecting small haptophytes tended to be lower under acidification while their putative hosts' abundance was enhanced, suggesting a direct and negative effect of OA on viral–host interactions. In the oligotrophic summer situation, we found a stimulating effect of OA on total viral abundance and the viral populations, suggesting a cascading effect of the elevated pCO2 stimulating autotrophic and heterotrophic production. In winter, viral lysis accounted for 30 ± 16% of the loss of bacterial standing stock per day (VMMBSS) under increased pCO2 compared to 53 ± 35% in the control treatments, without effects of nutrient additions while in summer, OA had no significant effects on VMMBSS (35 ± 20% and 38 ± 5% per day in the OA and control treatments, respectively). We found that phage production and resulting organic carbon release rates significantly reduced under OA in the nutrient replete winter situation, but it was also observed that high nutrient loads lowered the negative effect of OA on viral lysis, suggesting an antagonistic interplay between these two major global ocean stressors in the Anthropocene. In summer, however, viral-mediated carbon release rates were lower and not affected by lowered pH. Eutrophication consistently stimulated viral production regardless of the season or initial conditions. Given the relevant role of viruses for marine carbon cycling and the biological carbon pump, these two anthropogenic stressors may modulate carbon fluxes through their effect on viruses at the base of the pelagic food web in a future global change scenario.

Ocean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed "tropicalization". A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral-dominated systems. We conducted field surveys and in situ transplants at natural analogues for present and future conditions under (i) ocean warming and (ii) both ocean warming and acidification at a transition zone between kelp and coral-dominated ecosystems. We show that increased herbivory by warm-water fishes exacerbates kelp forest loss and that ocean acidification negates any benefits of warming for range extending tropical corals growth and physiology at temperate latitudes. Our data show that, as the combined effects of ocean acidification and warming ratchet up, marine coastal ecosystems lose kelp forests but do not gain scleractinian corals. Ocean acidification plus warming leads to overall habitat loss and a shift to simple turf-dominated ecosystems, rather than the complex coral-dominated tropicalized systems often seen with warming alone. Simplification of marine habitats by increased CO2 levels cascades through the ecosystem and could have severe consequences for the provision of goods and services.

Atmospheric CO2 concentration [CO2] has increased from a pre-industrial level of approximately 280 ppm to approximately 385 ppm, with further increases (700–1000 ppm) anticipated by the end of the twenty-first century [[1][1]]. Over the past three decades, changes in [CO2] have increased global

Rising atmospheric CO2 reduces seawater pH causing ocean acidification (OA). Understanding how resilient marine organisms respond to OA may help predict how community dynamics will shift as CO2 continues rising. The common slipper shell snail Crepidula fornicata is a marine gastropod native to eastern North America that has been a successful invader along the western European coastline and elsewhere. It has also been previously shown to be resilient to global change stressors. To examine the mechanisms underlying C. fornicata’s resilience to OA, we conducted two controlled laboratory experiments. First, we examined several phenotypes and genome-wide gene expression of C. fornicata in response to pH treatments (7.5, 7.6, and 8.0) throughout the larval stage and then tested how conditions experienced as larvae influenced juvenile stages (i.e., carry-over effects). Second, we examined genome-wide gene expression patterns of C. fornicata larvae in response to acute (4, 10, 24, and 48 h) pH treatment (7.5 and 8.0). Both C. fornicata larvae and juveniles exhibited resilience to OA and their gene expression responses highlight the role of transcriptome plasticity in this resilience. Larvae did not exhibit reduced growth under OA until they were at least 8 days old. These phenotypic effects were preceded by broad transcriptomic changes, which likely served as an acclimation mechanism for combating reduced pH conditions frequently experienced in littoral zones. Larvae reared in reduced pH conditions also took longer to become competent to metamorphose. In addition, while juvenile sizes at metamorphosis reflected larval rearing pH conditions, no carry-over effects on juvenile growth rates were observed. Transcriptomic analyses suggest increased metabolism under OA, which may indicate compensation in reduced pH environments. Transcriptomic analyses through time suggest that these energetic burdens experienced under OA eventually dissipate, allowing C. fornicata to reduce metabolic demands and acclimate to reduced pH. Carry-over effects from larval OA conditions were observed in juveniles; however, these effects were larger for more severe OA conditions and larvae reared in those conditions also demonstrated less transcriptome elasticity. This study highlights the importance of assessing the effects of OA across life history stages and demonstrates how transcriptomic plasticity may allow highly resilient organisms, like C. fornicata, to acclimate to reduced pH environments.

Understanding how declining seawater pH caused by anthropogenic carbon emissions, or ocean acidification, impacts Southern Ocean biota is limited by a paucity of pH time-series. Here, we present the first high-frequency in-situ pH time-series in near-shore Antarctica from spring to winter under annual sea ice. Observations from autonomous pH sensors revealed a seasonal increase of 0.3 pH units. The summer season was marked by an increase in temporal pH variability relative to spring and early winter, matching coastal pH variability observed at lower latitudes. Using our data, simulations of ocean acidification show a future period of deleterious wintertime pH levels potentially expanding to 7–11 months annually by 2100. Given the presence of (sub)seasonal pH variability, Antarctica marine species have an existing physiological tolerance of temporal pH change that may influence adaptation to future acidification. Yet, pH-induced ecosystem changes remain difficult to characterize in the absence of sufficient physiological data on present-day tolerances. It is therefore essential to incorporate natural and projected temporal pH variability in the design of experiments intended to study ocean acidification biology.

Understanding how declining seawater pH caused by anthropogenic carbon emissions, or ocean acidification, impacts Southern Ocean biota is limited by a paucity of pH time-series. Here, we present the first high-frequency in-situ pH time-series in near-shore Antarctica from spring to winter under annual sea ice. Observations from autonomous pH sensors revealed a seasonal increase of 0.3 pH units. The summer season was marked by an increase in temporal pH variability relative to spring and early winter, matching coastal pH variability observed at lower latitudes. Using our data, simulations of ocean acidification show a future period of deleterious wintertime pH levels potentially expanding to 7–11 months annually by 2100. Given the presence of (sub)seasonal pH variability, Antarctica marine species have an existing physiological tolerance of temporal pH change that may influence adaptation to future acidification. Yet, pH-induced ecosystem changes remain difficult to characterize in the absence of sufficient physiological data on present-day tolerances. It is therefore essential to incorporate natural and projected temporal pH variability in the design of experiments intended to study ocean acidification biology.

Anthropogenic greenhouse gas emissions increase sea surface temperature and acidification, inhibiting calcification of reef-building corals. While ocean acidification is known to hinder skeletal development of newly settled coral recruits, little is known of its effects on older purebred or interspecific hybrid recruits, or its combined effects with temperature. Using 3D X-ray microscopy, we found that predicted mid-century ocean warming and acidification conditions (28 °C, 685 ppm pCO2) negatively affected the skeletal development of 7-month-old Acropora purebreds and hybrids in one direction (Acropora cf. kenti mother x Acropora loripes father). Conversely, the skeletal parameters of reciprocal hybrids (A. loripes mother x A. cf. kenti father) remained unaffected. Skeletal measurements taken from 3D data revealed patterns overlooked by previous 2D measurements, leading support to the likelihood of hybrid vigour in hybrids of A. loripes (mother) and A. cf. kenti (father) and the potential of interspecific hybridization as a reef restoration tool to enhance coral resilience.

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 61:291-305 (2010) - DOI: https://doi.org/10.3354/ame01446 AME Special 4: Progress and perspectives in aquatic microbial ecology: Highlights of the SAME 11, Piran, Slovenia, 2009 Effect of ocean acidification on microbial diversity and on microbe-driven biogeochemistry and ecosystem functioning Jinwen Liu1,2,3, Markus G. Weinbauer1,2, Cornelia Maier1,2, Minhan Dai3, Jean-Pierre Gattuso1,2,* 1INSU-CNRS, Laboratoire d'Océanographie de Villefranche, BP 28, 06234 Villefranche-sur-mer Cedex, France 2Université Pierre et Marie Curie, Observatoire Océanologique de Villefranche, 06230 Villefranche-sur-mer, France 3State Key Laboratory of Marine Environmental Science, Xiamen University, 361005 Xiamen, China *Corresponding author. Email: gattuso@obs-vlfr.fr ABSTRACT: The ocean absorbs about 25% of anthropogenic CO2 emissions, which alters its chemistry. Among the changes of the carbonate system are an increase in the partial pressure of CO2 (pCO2) and a decline of pH; hence, the whole process is often referred to as 'ocean acidification'. Many microbial processes can be affected either directly or indirectly via a cascade of effects through the response of non-microbial groups and/or through changes in seawater chemistry. We briefly review the current understanding of the impact of ocean acidification on microbial diversity and processes, and highlight the gaps that need to be addressed in future research. The focus is on Bacteria, Archaea, viruses and protistan grazers but also includes total primary production of phytoplankton as well as species composition of eukaryotic phytoplankton. Some species and communities exhibit increased primary production at elevated pCO2. In contrast to their heterocystous counterparts, nitrogen fixation by non-heterocystous cyanobacteria is stimulated by elevated pCO2. The experimental data on the response of prokaryotic production to ocean acidification are not consistent. Very few other microbial processes have been investigated at environmentally relevant pH levels. The potential for microbes to adapt to ocean acidification, at either the species level by genetic change or at the community level through the replacement of sensitive species or groups by non- or less sensitive ones, is completely unknown. Consequently, the impact of ocean acidification on keystone species and microbial diversity needs to be elucidated. Most experiments used a short-term perturbation approach by using cultured organisms; few were conducted in mesocosms and none in situ. There is likely a lot to be learned from observations in areas naturally enriched with CO2, such as vents, upwelling and near-shore areas. KEY WORDS: Ocean acidification · Microbial diversity · Microbe · Bacteria · Phytoplankton · Viruses á Biogeochemistry · Meta-analysis Full text in pdf format PreviousCite this article as: Liu J, Weinbauer MG, Maier C, Dai M, Gattuso JP (2010) Effect of ocean acidification on microbial diversity and on microbe-driven biogeochemistry and ecosystem functioning. Aquat Microb Ecol 61:291-305. https://doi.org/10.3354/ame01446 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 61, No. 3. Online publication date: December 30, 2010 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2010 Inter-Research.

<scp>ASLO</scp> 2020 Award Winners

Seasonal and inter-annual variability of air–sea CO 2 fluxes and seawater carbonate chemistry in the Southern North Sea

Impacts of climate change on methylmercury formation and bioaccumulation in the 21st century ocean

Abstract. Coastal and estuarine waters of the northern California Current system and southern Salish Sea host an observational network capable of characterizing biogeochemical dynamics related to ocean acidification, hypoxia, and marine heatwaves. Here, we compiled data sets from a set of cruises conducted in estuarine waters of Puget Sound (southern Salish Sea) and its boundary waters (Strait of Juan de Fuca and Washington coast). This data product provides data from a decade of cruises with consistent formatting, extended data quality control, and multiple units for parameters such as oxygen with different end use needs and conventions. All cruises obtained high-quality temperature, salinity, inorganic carbon, nutrient, and oxygen observations to provide insight into the dynamic distribution of physical and biogeochemical conditions in this large urban estuary complex on the west coast of North America. At all sampling stations, conductivity–temperature–depth (CTD) casts included sensors for measuring temperature, conductivity, pressure, and oxygen concentrations. Laboratory analyses of discrete water samples collected at all stations throughout the water column in Niskin bottles provided measurements of dissolved inorganic carbon (DIC), dissolved oxygen, nutrient (nitrate, nitrite, ammonium, phosphate, and silicate), and total alkalinity (TA) content. This data product includes observations from 35 research cruises, including 715 oceanographic profiles, with &gt;7490 sensor measurements of temperature, salinity, and oxygen; ≥6070 measurements of discrete oxygen and nutrient samples; and ≥4462 measurements of inorganic carbon variables (i.e., DIC and TA). The observations comprising this cruise compilation collectively characterize the spatial and temporal variability in a region with large dynamic ranges of the physical (temperature = 6.0–21.8 ∘C, salinity = 15.6–34.0) and biogeochemical (oxygen = 12–481 µmol kg−1, dissolved inorganic carbon = 1074–2362 µmol kg−1, total alkalinity = 1274–2296 µmol kg−1) parameters central to understanding ocean acidification and hypoxia in this productive estuary system with numerous interacting human impacts on its ecosystems. All observations conform to the climate-quality observing guidelines of the Global Ocean Acidification Observing Network, the US National Oceanic and Atmospheric Administration's Ocean Acidification Program, and ocean carbon community best practices. This ongoing cruise time series supports the estuarine and coastal monitoring and research objectives of the Washington Ocean Acidification Center and US National Oceanic and Atmospheric Administration (NOAA) Ocean and Atmospheric Research programs, and it provides diverse end users with the information needed to frame biological impacts research, validate numerical models, inform state and tribal water quality and fisheries management, and support decision-makers. All 2008–2018 cruise time-series measurements used in this publication are available at https://doi.org/10.25921/zgk5-ep63 (Alin et al., 2022).

Abstract. Ocean acidification from the uptake of anthropogenic carbon is simulated for the industrial period and IPCC SRES emission scenarios A2 and B1 with a global coupled carbon cycle-climate model. Earlier studies identified seawater saturation state with respect to aragonite, a mineral phase of calcium carbonate, as a key variable governing impacts on corals and other shell-forming organisms. Globally in the A2 scenario, water saturated by more than 300%, considered suitable for coral growth, vanishes by 2070 AD (CO2≈630 ppm), and the ocean volume fraction occupied by saturated water decreases from 42% to 25% over this century. The largest simulated pH changes worldwide occur in Arctic surface waters, where hydrogen ion concentration increases by up to 185% (ΔpH=−0.45). Projected climate change amplifies the decrease in Arctic surface mean saturation and pH by more than 20%, mainly due to freshening and increased carbon uptake in response to sea ice retreat. Modeled saturation compares well with observation-based estimates along an Arctic transect and simulated changes have been corrected for remaining model-data differences in this region. Aragonite undersaturation in Arctic surface waters is projected to occur locally within a decade and to become more widespread as atmospheric CO2 continues to grow. The results imply that surface waters in the Arctic Ocean will become corrosive to aragonite, with potentially large implications for the marine ecosystem, if anthropogenic carbon emissions are not reduced and atmospheric CO2 not kept below 450 ppm.