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Whether marine fish will grow differently in future high pCO2 environments remains surprisingly uncertain. Long-term and whole-life cycle effects are particularly unknown, because such experiments are logistically challenging, space demanding, exclude long-lived species, and require controlled, restricted feeding regimes—otherwise increased consumption could mask potential growth effects. Here, we report on repeated, long-term, food-controlled experiments to rear large populations (>4,000 individuals total) of the experimental model and ecologically important forage fish Menidia menidia (Atlantic silverside) under contrasting temperature (17°, 24°, and 28°C) and pCO2 conditions (450 vs. 2,200 μatm) from fertilization to a third of this annual species' life span. Quantile analyses of trait distributions showed mostly negative effects of high pCO2 on long-term growth. At 17°C and 28°C, but not at 24°C, high pCO2 fish were significantly shorter [17°C: -5 to -9%; 28°C: -3%] and weighed less [17°C: -6 to -18%; 28°C: -8%] compared to ambient pCO2 fish. Reductions in fish weight were smaller than in length, which is why high pCO2 fish at 17°C consistently exhibited a higher Fulton's k (weight/length ratio). Notably, it took more than 100 days of rearing for statistically significant length differences to emerge between treatment populations, showing that cumulative, long-term CO2 effects could exist elsewhere but are easily missed by short experiments. Long-term rearing had another benefit: it allowed sexing the surviving fish, thereby enabling rare sex-specific analyses of trait distributions under contrasting CO2 environments. We found that female silversides grew faster than males, but there was no interaction between CO2 and sex, indicating that males and females were similarly affected by high pCO2. Because Atlantic silversides are known to exhibit temperature-dependent sex determination, we also analyzed sex ratios, revealing no evidence for CO2-dependent sex determination in this species. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2020) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2020-12-25.

In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2022) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2023-10-17. This dataset includes physiological parameters of three Hawaiian coral species (Porites compressa, Porites lobata, and Montipora capitata) over 22-month mesocosm experiment. The corals were exposed to one of four treatments: control, ocean acidification, ocean warming, or combined future ocean conditions.

Ambient conditions shape microbiome responses to both short- and long-duration environment changes through processes including physiological acclimation, compositional shifts, and evolution. Thus, we predict that microbial communities inhabiting locations with larger diel, episodic, and annual variability in temperature and pH should be less sensitive to shifts in these climate-change factors. To test this hypothesis, we compared responses of surface ocean microbes from more variable (nearshore) and more constant (offshore) sites to short-term factorial warming (+3 °C) and/or acidification (pH -0.3). In all cases, warming alone significantly altered microbial community composition, while acidification had a minor influence. Compared with nearshore microbes, warmed offshore microbiomes exhibited larger changes in community composition, phylotype abundances, respiration rates, and metatranscriptomes, suggesting increased sensitivity of microbes from the less-variable environment. Moreover, while warming increased respiration rates, offshore metatranscriptomes yielded evidence of thermal stress responses in protein synthesis, heat shock proteins, and regulation. Future oceans with warmer waters may enhance overall metabolic and biogeochemical rates, but they will host altered microbial communities, especially in relatively thermally stable regions of the oceans. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Gattuso et al, 2019) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2020-10-20.

Rising atmospheric CO2 concentrations threaten coral reefs globally by causing ocean acidification (OA) and warming. Yet, the combined effects of elevated pCO2 and temperature on coral physiology and resilience remain poorly understood. While coral calcification and energy reserves are important health indicators, no studies to date have measured energy reserve pools (i.e., lipid, protein, and carbohydrate) together with calcification under OA conditions under different temperature scenarios. Four coral species, Acropora millepora, Montipora monasteriata, Pocillopora damicornis, Turbinaria reniformis, were reared under a total of six conditions for 3.5 weeks, representing three pCO2 levels (382, 607, 741 µatm), and two temperature regimes (26.5, 29.0°C) within each pCO2 level. After one month under experimental conditions, only A. millepora decreased calcification (-53%) in response to seawater pCO2 expected by the end of this century, whereas the other three species maintained calcification rates even when both pCO2 and temperature were elevated. Coral energy reserves showed mixed responses to elevated pCO2 and temperature, and were either unaffected or displayed nonlinear responses with both the lowest and highest concentrations often observed at the mid-pCO2 level of 607 µatm. Biweekly feeding may have helped corals maintain calcification rates and energy reserves under these conditions. Temperature often modulated the response of many aspects of coral physiology to OA, and both mitigated and worsened pCO2 effects. This demonstrates for the first time that coral energy reserves are generally not metabolized to sustain calcification under OA, which has important implications for coral health and bleaching resilience in a high-CO2 world. Overall, these findings suggest that some corals could be more resistant to simultaneously warming and acidifying oceans than previously expected. In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne et al, 2014) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2014-07-08. Supplement to: Schoepf, Verena; Grottoli, Andréa G; Warner, Mark E; Cai, Wei-Jun; Melman, Todd F; Hoadley, Kenneth D; Pettay, D Tye; Hu, Xinping; Li, Qian; Xu, Hui; Wang, Yujie; Matsui, Yohei; Baumann, Justin H (2013): Coral Energy Reserves and Calcification in a High-CO2 World at Two Temperatures. PLoS ONE, 8(10), e75049

From 26 December 2012 to 21 January 2013 we measured relevant parameters for surface energy and mass exchange calculation at three closely collocated sites near the Ross Sea shore in the valley floor of lower Taylor Valley, McMurdo Dry Valleys, Antarctica. At any time during the experiment, two surface energy balance stations were operated: One station was installed throughout the whole period at the investigated water track, referred to as WT. The other station was operated as a reference representing the dominant non-water track (NWT), bare soil surfaces in lower Taylor Valley; it was successively installed at two sites with different soil textures: PLD was located on a paleolake delta dominated by fine surficial sediments, while GT represented coarse glacial till. At each station the following instruments were installed: A net radiometer (NR01, Hukseflux Thermal Sensors B.V., Delft, NL) was used for measuring solar and terrestrial radiation, an ultrasonic anemometer (81000 VRE, R.M. Young Company, Traverse City, MI, USA) and an infrared gas analyzer (LI-7500, LI-COR Inc., Lincoln, NE, USA) recorded data for turbulent heat flux estimation via the eddy-covariance method. Thermistors and thermocouples recorded soil temperatures in several depths in the thawed layer. Additionally, we used a thermal properties analyzer (KD2 Pro, Decagon Devices, Pullman, WA, USA) for measuring soil thermal properties for several samples taken from the surface. Eddy-covariance processing was done with the bmmflux tool of the University of Bayreuth (see appendix in Thomas et al., 2009), including data quality assessment after Foken et al. (2004). Turbulent flux footprints were modeled with the TERRAFEX model of the University of Bayreuth (Göckede, 2001) which provided contributions of adjacent land cover types to the flux footprint. Further information on the experimental setup can be found in Linhardt et al. (2019).

Behavioural impairment following exposure to ocean acidification-relevant CO2 levels has been noted in a broad array of taxa. The underlying cause of these disruptions is thought to stem from alterations of ion gradients ([HCO3]−/Cl−) across neuronal cell membranes that occur as a consequence of maintaining pH homeostasis via the accumulation of [HCO3]−. While behavioural impacts are widely documented, few studies have measured acid–base parameters in species showing behavioural disruptions. In addition, current studies examining mechanisms lack resolution in targeting specific neural pathways corresponding to a given behaviour. With these considerations in mind, acid–base parameters and behaviour were measured in a model organism used for decades as a research model to study learning, the California sea hare (Aplysia californica). Aplysia exposed to elevated CO2 increased haemolymph [HCO3]−, achieving full and partial pH compensation at 1200 and 3000 µatm CO2, respectively. Increased CO2 did not affect self-righting behaviour. In contrast, both levels of elevated CO2 reduced the time of the tail-withdrawal reflex, suggesting a reduction in antipredator response. Overall, these results confirm that Aplysia are promising models to examine mechanisms underlying CO2-induced behavioural disruptions since they regulate [HCO3]− and have behaviours linked to neural networks amenable to electrophysiological testing.

Atmospheric monitoring of high northern latitudes (> 40°N) has shown an enhanced seasonal cycle of carbon dioxide (CO2) since the 1960s but the underlying mechanisms are not yet fully understood. The much stronger increase in high latitudes compared to low ones suggests that northern ecosystems are experiencing large changes in vegetation and carbon cycle dynamics. Here we show that the latitudinal gradient of the increasing CO2 amplitude is mainly driven by positive trends in photosynthetic carbon uptake caused by recent climate change and mediated by changing vegetation cover in northern ecosystems. Our results emphasize the importance of climate-vegetation-carbon cycle feedbacks at high latitudes, and indicate that during the last decades photosynthetic carbon uptake has reacted much more strongly to warming than carbon release processes.

Ocean acidification (OA) is predicted to reduce reef coral calcification rates and threaten the long-term growth of coral reefs under climate change. Reduced coral growth at elevated pCO2 may be buffered by sufficiently high irradiances; however, the interactive effects of OA and irradiance on other fundamental aspects of coral physiology, such as the composition and energetics of coral biomass, remain largely unexplored. This study tested the effects of two light treatments (7.5 versus 15.7 mol photons/m**2/d) at ambient or elevated pCO2 (435 versus 957 µatm) on calcification, photopigment and symbiont densities, biomass reserves (lipids, carbohydrates, proteins), and biomass energy content (kJ) of the reef coral Pocillopora acuta from Kāne'ohe Bay, Hawai'i. While pCO2 and light had no effect on either area- or biomass-normalized calcification, tissue lipids/gdw and kJ/gdw were reduced 15% and 14% at high pCO2, and carbohydrate content increased 15% under high light. The combination of high light and high pCO2 reduced protein biomass (per unit area) by approximately 20%. Thus, under ecologically relevant irradiances, P. acuta in Kāne'ohe Bay does not exhibit OA-driven reductions in calcification reported for other corals; however, reductions in tissue lipids, energy content and protein biomass suggest OA induced an energetic deficit and compensatory catabolism of tissue biomass. The null effects of OA on calcification at two irradiances support a growing body of work concluding some reef corals may be able to employ compensatory physiological mechanisms that maintain present-day levels of calcification under OA. However, negative effects of OA on P. acuta biomass composition and energy content may impact the long-term performance and scope for growth of this species in a high pCO2 world.

Reconstructing the evolution of sea level during past warmer epochs such as the Pliocene provides insight into the response of sea level and ice sheets to prolonged warming. Although estimates of global mean sea level (GMSL) during this time do exist, they vary by several tens of metres, hindering the assessment of past and future ice-sheet stability. Here we show that during the mid-Piacenzian Warm Period, which was on average 2-3 degrees Celsius warmer than the pre-industrial period, the GMSL (sea-level equivalent changes in global ice volume) was about 16.2 metres higher than today. During the even warmer Pliocene Climatic Optimum (about 4 degrees Celsius warmer than pre-industrial), our results show that GMSL was 23.5 metres above the present level (m.a.p.s.l.). We present six GMSL data points, ranging from 4.39 to 3.27 million years ago, that are based on overgrowths on phreatic (from water-filled caves) speleothems from the western Mediterranean Sea, near Mallorca, Spain. This record is unique owing to its clear relationship to sea level, its reliable U-Pb ages and its long timespan, which allows us to quantify uncertainties on potential uplift. Our data indicate that ice sheets are very sensitive to warming and provide important calibration targets for future ice-sheet models.