High pCO2 Research Articles

Higher sensitivity towards light stress and ocean acidification in an Arctic sea-ice-associated diatom compared to a pelagic diatom.

Thalassiosira hyalina and Nitzschia frigida are important members of Arctic pelagic and sympagic (sea-ice-associated) diatom communities. We investigated the effects of light stress (shift from 20 to 380µmolphotonsm-2 s-1 , resembling upwelling or ice break-up) under contemporary and future pCO2 (400 vs 1000µatm). The responses in growth, elemental composition, pigmentation and photophysiology were followed over 120h and are discussed together with underlying gene expression patterns. Stress response and subsequent re-acclimation were efficiently facilitated by T.hyalina, which showed only moderate changes in photophysiology and elemental composition, and thrived under high light after 120h. In N.frigida, photochemical damage and oxidative stress appeared to outweigh cellular defenses, causing dysfunctional photophysiology and reduced growth. pCO2 alone did not specifically influence gene expression, but amplified the transcriptomic reactions to light stress, indicating that pCO2 affects metabolic equilibria rather than sensitive genes. Large differences in acclimation capacities towards high light and high pCO2 between T.hyalina and N.frigida indicate species-specific mechanisms in coping with the two stressors, which may reflect their respective ecological niches. This could potentially alter the balance between sympagic and pelagic primary production in a future Arctic.

Blood Gas Disturbances and Disproportionate Body Weight Distribution in Broilers With Wooden Breast.

Wooden breast syndrome is a widespread and economically important myopathy and vasculopathy of fast growing, commercial broiler chickens, primarily affecting birds with high feed efficiency and large breast muscle yield. To investigate potential systemic physiological differences between birds affected and unaffected by wooden breast, a total of 103 market-age Cobb 500 broilers were sampled for 13 blood parameters and the relative weights of the pectoralis major muscle, pectoralis minor muscle, external oblique muscle, wing, heart, lungs, liver, and spleen. Blood analysis was performed on samples taken from the brachial vein of live birds and revealed significant differences in venous blood gases between affected and unaffected chickens. Chickens with wooden breast exhibited significantly higher potassium (K+) and lower partial pressure of oxygen (pO2), oxygen saturation (sO2), and pH. Additionally, affected males had significantly higher partial pressure of carbon dioxide (pCO2) and total carbon dioxide (TCO2) than unaffected males. Wooden breast affected broilers also possessed a significantly heavier pectoralis major muscle and whole feathered wing compared to unaffected broilers. Blood gas disturbances characterized by high pCO2 and low pH are indicative of insufficient respiratory gas exchange, suggesting that wooden breast affected broilers have an elevated metabolic rate that may also be inadequately compensated due to cardiovascular deficiencies such as poor venous return or respiratory insufficiency. Lung tissues from 12 birds with extreme sO2 values were subsequently examined to assess whether lung pathology contributed to the observed blood gas disturbance. Comparison of lung morphology between affected and unaffected birds revealed no apparent differences that could contribute to decreased parabronchial gas exchange. However, an interesting finding was the detection of pulmonary phlebitis in one of the wooden breast-affected samples consistent with vascular changes observed in pectoralis major muscle exhibiting the wooden breast phenotype. Our results suggest that the effects of wooden breast are not limited to the pectoralis major muscle and further indicate the importance of research into metabolic changes associated with the myopathy.

Air–Sea CO2 dynamics from tropical estuarine system Mahanadi, India

The biogeochemical characteristics of Mahanadi estuarine system in eastern India were investigated to understand the seasonality in carbon parameters and their influence on sea–air CO2 gradient. In general, the stations close to the estuary had higher salinity and total alkalinity; and lower pCO2(water) relative to the inner most stations. In contrast, the riverine stations had low pH and high pCO2(water) and lower total alkalinity. The chlorophyll a values ranged between 0.27 to 11.22 mg m−3 during this investigation. We found that the seasonal oscillations in sea–air CO2 gradient (ΔpCO2 = pCO2(water)–pCO2(air)) were negative during winter and positive during summer, wherein the estuary acted as a weak source. The average air–water CO2 flux density values varied between −5.65 to 13.11 μmol m−2 h−1 throughout the study period. Two-way ANOVA showed strong seasonal control on environmental variables. The relationships observed between pH and salinity with pCO2 suggest that fluvial inputs of nutrients and the accompanying heterotrophic processes may possibly control the sea–air CO2 gradient in the surface waters of the Mahanadi estuary.

A Mathematical Model of the Rat Kidney. II. Antidiuresis

Water conservation by the kidney requires a hypertonic medullary interstitium, NaCl in outer medulla (OM) and both NaCl and urea in inner medulla (IM), along with a vascular configuration that protects against washout. A multi‐solute mathematical model of the rat kidney, which includes the important acid‐base species, was developed and used first to examine K+‐induced natriuresis (Am. J. Physiol. 312:F925, 2017). In the present work, model computation has been streamlined by parallelizing the calculation of the model Jacobian, and this has allowed finer medullary spatial resolution, along with more extensive examination of model parameters. Tubule compliance is now represented along the whole nephron, and this attenuates pressure swings due to variations in urine flow. OM NaCl is modestly increased when transporter density in ascending Henle limbs (AHL) from juxtamedullary nephrons (JM), is scaled to match the greater JM nephron solute flow. However, higher NaCl transport produces greater CO2 generation, and by virtue of countercurrent vascular flows, establishment of high medullary pCO2. This CO2 gradient can be mitigated, by assuming that a fraction of medullary AHL and collecting duct transport is powered anaerobically. Reduction of vascular flows or increasing vessel permeabilities does little to further increase OM solute gradients. In contrast to the medullary models of others, vessels in this model all have solute reflection coefficients close to zero; increasing these coefficients provides no substantive enhancement of solute profiles, but does generate high interstitial hydrostatic pressures, which distort tubule architecture. As others have noted, increasing medullary urea delivery via entering vasa recta, enhances IM urea, although not nearly to levels found in rats. In sum, (1) the magnitudes of medullary gradients of Na+, urea, and ammonia are still not captured by the model; and (2) the countercurrent architecture that provides antidiuresis also produces exaggerated pCO2 profiles and appears to be an unappreciated constraint on models of medullary function.Support or Funding InformationNIH RO1‐DK‐29857

Mineralogical constraints on Neoproterozoic pCO2 and marine carbonate chemistry

Abstract Numerous investigators have sought to identify the perturbations to the global carbon cycle that fueled Earth system change during the Neoproterozoic Era. Nevertheless, a lack of constraints on ocean-atmosphere carbon chemistry has precluded efforts to link biology, climate, and the lithosphere. We combined field and petrographic observations with experimental and theoretical geochemistry to show that early Neoproterozoic seawater featured elevated alkalinity in the presence of high atmospheric pCO2, which sustained remarkable marine CaCO3 supersaturation (Ωcalcite). Without pelagic calcification, Neoproterozoic marine Ωcalcite and pCO2 would have been mediated principally by CaCO3 precipitation kinetics; thus, secular changes in kinetic inhibitors to CaCO3 nucleation may have destabilized the global carbon cycle.

The effects of elevated CO2 concentrations on changes in fatty acids and amino acids of three species of microalgae

ABSTRACT Microalgae are important producers in aquatic ecosystems and are valuable for biodiesel production and feed supply industries. Three such microalgae, Nannochloropsis oceanica (Eustigmatophyceae), Dunaliella salina (Chlorophyceae), and Chlamydomonas reinhardtii (Chlorophyceae), were cultured at two pCO2 (400 ppm, 1000 ppm) to investigate changes in fatty acid and amino acid composition. Elevated pCO2 increased C16:0, C18:3, C20:5, total saturated fatty acid (SFA), total polyunsaturated fatty acid (PUFA), and total essential amino acid (EAA) content in N. oceanica. High CO2 concentration reduced C16:0 and total SFA content, but increased C18:3, total PUFA, and total EAA accumulation, in D. salina. Changes in C. reinhardtii were the opposite of those in D. salina. Results indicated that higher pCO2 may improve the quality of biodiesel produced by N. oceanica and C. reinhardtii. Furthermore, in N. oceanica and D. salina, increased CO2 concentration elevated nutrient levels but resulted in reduced nutrient quality in C. reinhardtii. Our results can help predict nutritional changes in microalgae at elevated pCO2, and provide insight into production of biodiesel and animal feed by microalgae.

Resistance of seagrass habitats to ocean acidification via altered interactions in a tri-trophic chain

Despite the wide knowledge about prevalent effects of ocean acidification on single species, the consequences on species interactions that may promote or prevent habitat shifts are still poorly understood. Using natural CO2 vents, we investigated changes in a key tri-trophic chain embedded within all its natural complexity in seagrass systems. We found that seagrass habitats remain stable at vents despite the changes in their tri-trophic components. Under high pCO2, the feeding of a key herbivore (sea urchin) on a less palatable seagrass and its associated epiphytes decreased, whereas the feeding on higher-palatable green algae increased. We also observed a doubled density of a predatory wrasse under acidified conditions. Bottom-up CO2 effects interact with top-down control by predators to maintain the abundance of sea urchin populations under ambient and acidified conditions. The weakened urchin herbivory on a seagrass that was subjected to an intense fish herbivory at vents compensates the overall herbivory pressure on the habitat-forming seagrass. Overall plasticity of the studied system components may contribute to prevent habitat loss and to stabilize the system under acidified conditions. Thus, preserving the network of species interactions in seagrass ecosystems may help to minimize the impacts of ocean acidification in near-future oceans.

A single-center observational study on congenital diaphragmatic hernia: Outcome, predictors of mortality and experience from a tertiary perinatal center in Singapore

Congenital diaphragmatic hernia (CDH) is a common birth defect associated with significant mortality and morbidity. There is limited outcome data on CDH in the Southeast Asian region. Rapid accessibility to our CDH Perinatal Center, as a consequence of the small geographic size of our country and efficient land transportation system, has largely eliminated deaths of live outborn babies prior arrival at our center. We selected a study period when extracorporeal membrane oxygenation (ECMO) support was not available at our institution. The data will therefore be relevant in developing management guidelines and antenatal counselling for perinatal centers in this region managing CDH with limited resources, without ECMO facilities. A retrospective study of antenatally or postnatally diagnosed CDH infants born between January 2002 and June 2005 was performed. We selected this study period as ECMO support was not available over this period. We studied the demographics, clinical characteristics, postnatal predictors of mortality and outcomes of CDH infants in a single tertiary institution. A total of 24 patients with CDH were identified. Seventy-nine percent of liveborns with CDH survived to hospital discharge. Antenatal detection rate was 83.3%. Significant postnatal predictors of mortality were preoperative pneumothorax (p=0.035), high CRIB score (p=0.007), low one- and five-minute Apgar score (p=0.011, p=0.026 respectively) and high pCO2 on initial arterial blood gas (p=0.007). At one-year follow-up, three patients had delayed gross motor milestones which resolved subsequently. Re-admissions were required for recurrent bronchiolitis (33%) and oesophageal reflux which resolved in all cases. Two (13.3%) infants had surgical complications and needed re-admission for probable adhesive intestinal obstruction; one required adhesiolysis and the other was managed conservatively with good outcome. A single-center CDH outcome in Singapore, without ECMO use, was good. This is a cohort now with long-term survival outcome which will be valuable to the neonatology community.

Elevated pCO2 Level Affects the Extracellular Polymer Metabolism of Phaeodactylum tricornutum.

Extracellular polymeric substances (EPS) play an important role in diatom physiology and carbon biogeochemical cycling in marine ecosystems. Both the composition and yield of EPS in diatom cells can vary with environmental changes. However, information on intracellular pathways and controls of both biochemical and genetic of EPS is limited. Further, how such changes would affect their critical ecological roles in marine systems is also unclear. Here, we evaluated the physiological characteristics, EPS yields, EPS compositions, and gene expression levels of Phaeodactylum tricornutum under elevated pCO2 levels. Genes and pathways related to EPS metabolism in P. tricornutum were identified. Carbohydrate yields in different EPS fractions increased with elevated pCO2 exposure. Although the proportions of monosaccharide sugars among total sugars did not change, higher abundances of uronic acid were observed under high pCO2 conditions, suggesting the alterations of EPS composition. Elevated pCO2 increased PSII light energy conversion efficiency and carbon sequestration efficiency. The up-regulation of most genes involved in carbon fixation pathways led to increased growth and EPS release. RNA-Seq analysis revealed a number of genes and divergent alleles related to EPS production that were up-regulated by elevated pCO2 levels. Nucleotide diphosphate (NDP)-sugar activation and accelerated glycosylation could be responsible for more EPS responding to environmental signals. Further, NDP-sugar transporters exhibited increased expression levels, suggesting roles in EPS over-production. Overall, these results provide critical data for understanding the mechanisms of EPS production in diatoms and evaluating the metabolic plasticity of these organisms in response to environmental changes.

HYPO PERFUSION MARKERS AS THERAPEUTIC AND PROGNOSTIC TOOLS FOR SEPTIC PATIENTS

Background: Venous-to-arterial carbon dioxide difference (PvaCO2) and central venous oxygen saturation (ScvO2) may reflect the adequacy of blood flow during septic shock states. We sought to test whether the development of Pv-aCO2 and ScvO2 during the early phases of resuscitation is related to multi-organ dysfunction and outcomes in a population of septic shock patients resuscitated targeting the usual oxygen-derived and hemodynamic parameters. Aim of the Work: To assess the central venous-arterial carbon dioxide difference (Pv-aCO2) as a goal in goal directed therapy of sepsis resuscitation in comparison to central venous oxygen saturation (ScvO2) and to test for their prognostic values. Patients and Methods: This prospective observational study was performed in a 24-bed mixed ICU in a university-affiliated hospital. We examined all septic patients with a new episode admitted to the emergency room or proceeding from clinical wards during a 24-month period. After approval by Ethical Medical Committee and obtaining informed consent, simultaneous blood samples were collected from the central venous line and the arterial catheter for obtaining venous and arterial gases respectively at (T0), and 6 hours (T6), 12 hours (T12) and 24 hours (T24) later. Patients were classified into four groups; two group (30patients) (A1 and A2) according to PcvO2 gap and another two groups (30patients) (B1 andB2) according to Central venous oxygen saturation. Group (A1) Decreasing Pcv-aCO2 (high at T0, declining at T6), Group (A2) Persistently high Pcv-aCO2 (high at T0 and T6), Group (B1) Increasing Central venous oxygen saturation (less than 70% at T0, increasing at T6), Group (B2) Decreasing Central venous oxygen saturation (less than 70%at T0 and decreasing T6). Results: Sixty-eight septic critically ill patients were included in this study. However; 8 patients were excluded from the study. Among the included patients in the study, 3 patients were excluded as they developed acute coronary syndrome, 4 patients refused to complete the treatment and discharged against medical advice, and 1 patientdeveloped an ischemic cerebral vascular stroke. The final sample was therefore 60 patients. In this study, Central veno-arterial PCO2 gap and ScvO2 are considered as surrogate markers of the payment of the oxygen debt and early predictors of clinical outcome and organ dysfunction in the ICU. As regard the study, Central veno-arterial PCO2 gap is predictors for resuscitation in septic patients. As regard A Group, there was significant statistical difference between mortality and survival at T6, T12 and T24. However; regarding B Group, there was significant statistical difference between mortality and survival at T12 and T24. Also, this study shows that patients with persistently low ScvO2 are considered a good hypo perfusion marker for septic patients. Conclusion: Data support the hypothesis that persistence of high PCO2 Gap and low ScvO2 during the resuscitation of septic patients is associated with significant higher multi-organ dysfunction and poor outcomes in critically-ill patients. Recommendations: Future studies on a larger number of patients are needed and should test PCO2 Gap and ScvO2 as perfusion goals during early phases of the resuscitation of patients in septic shock to confirm its reliability.

A mathematical model of the rat kidney. II. Antidiuresis.

Kidney water conservation requires a hypertonic medullary interstitium, NaCl in the outer medulla and NaCl and urea in the inner medulla, plus a vascular configuration that protects against washout. In this work, a multisolute model of the rat kidney is revisited to examine its capacity to simulate antidiuresis. The first step was to streamline model computation by parallelizing its Jacobian calculation, thus allowing finer medullary spatial resolution and more extensive examination of model parameters. It is found that outer medullary NaCl is modestly increased when transporter density in ascending Henle limbs from juxtamedullary nephrons is scaled to match the greater juxtamedullary solute flow. However, higher NaCl transport produces greater CO2 generation and, by virtue of countercurrent vascular flows, establishment of high medullary Pco2. This CO2 gradient can be mitigated by assuming that a fraction of medullary transport is powered anaerobically. Reducing vascular flows or increasing vessel permeabilities does little to further increase outer medullary solute gradients. In contrast to medullary models of others, vessels in this model have solute reflection coefficients close to zero; increasing these coefficients provides little enhancement of solute profiles but does generate high interstitial pressures, which distort tubule architecture. Increasing medullary urea delivery via entering vasa recta increases inner medullary urea, although not nearly to levels found in rats. In summary, 1) medullary Na+ and urea gradients are not captured by the model and 2) the countercurrent architecture that provides antidiuresis also produces exaggerated Pco2 profiles and is an unappreciated constraint on models of medullary function.

Prognostic value of venous blood analysis at the start of CPR in non-traumatic out-of-hospital cardiac arrest: association with ROSC and the neurological outcome

BackgroundThe knowledge of new prognostic factors in out-of-hospital cardiac arrest (OHCA) that can be evaluated since the beginning of cardiopulmonary resuscitation (CPR) manoeuvres could be helpful in the decision-making process of prehospital care. We aim to identify metabolic variables at the start of advanced CPR at the scene that may be associated with two main outcomes of CPR (recovery of spontaneous circulation (ROSC) and neurological outcome).MethodsProspective observational study of all non-traumatic OHCA in patients older than 17 years assisted by emergency medical services (EMS), with doctor and nurse on board, between January 2012 and December 2017. Venous blood gases were sampled upon initially obtaining venous access to determine the initial values of pH, pCO2, HCO3−, base excess (BE), Na+, K+, Ca2+ and lactate. ROSC upon arrival at the hospital and neurological status 30 days later (Cerebral Performance Categories (CPC) scale) were recorded.ResultsWe included 1552 patients with OHCA with blood test data in a 6-year period. ROSC was achieved in 906 cases (58.4%), and good neurological recovery at 30 days (CPC I-II) occurred in 383 cases (24.68%). In multivariate analysis, we found a significant relationship between non-recovery of spontaneous circulation (no-ROSC) and low pH levels (adjusted odds ratio (OR) 0.03 (0.002–0.59), p = 0.020), high pCO2 levels (adjusted OR 1.03 [1.01–1.05], p = 0.008) and high potassium levels (adjusted OR 2.28 [1.43–3.61], p = 0.008). Poor neurological outcomes were associated with low pH levels (adjusted OR 0.06 [0.02–0.18], p < 0.001), high pCO2 (adjusted OR 1.05 [1.03–1.08], p < 0.001), low HCO3− (adjusted OR 0.97 [0.94–0.999], p = 0.044), low BE (adjusted OR 0.96 [0.93–0.98], p < 0.001) and high potassium levels (adjusted OR 1.37 [1.16–1.60], p < 0.001).ConclusionThere is a significant relationship between severe alterations of venous blood-gas variables and potassium at the start of CPR of non-traumatic OHCA and low-ROSC rate and neurological prognosis.

Symbiont community diversity is more variable in corals that respond poorly to stress.

Coral reefs are declining globally as climate change and local water quality press environmental conditions beyond the physiological tolerances of holobionts-the collective of the host and its microbial symbionts. To assess the relationship between symbiont composition and holobiont stress tolerance, community diversity metrics were quantified for dinoflagellate endosymbionts (Family: Symbiodiniaceae) from eight Acropora millepora genets that thrived under or responded poorly to various stressors. These eight selected genets represent the upper and lower tails of the response distribution of 40 coral genets that were exposed to four stress treatments (and control conditions) in a 10-day experiment. Specifically, four 'best performer' coral genets were analyzed at the end of the experiment because they survived high temperature, high pCO2 , bacterial exposure, or combined stressors, whereas four 'worst performer' genets were characterized because they experienced substantial mortality under these stressors. At the end of the experiment, seven of eight coral genets mainly hosted Cladocopium symbionts, whereas the eighth genet was dominated by both Cladocopium and Durusdinium symbionts. Symbiodiniaceae alpha and beta diversity were higher in worst performing genets than in best performing genets. Symbiont communities in worst performers also differed more after stress exposure relative to their controls (based on normalized proportional differences in beta diversity), than did best performers. A generalized joint attribute model estimated the influence of host genet and treatment on Symbiodiniaceae community composition and identified strong associations among particular symbionts and host genet performance, as well as weaker associations with treatment. Although dominant symbiont physiology and function contribute to host performance, these findings emphasize the importance of symbiont community diversity and stochasticity as components of host performance. Our findings also suggest that symbiont community diversity metrics may function as indicators of resilience and have potential applications in diverse disciplines from climate change adaptation to agriculture and medicine.

Food availability modulates the combined effects of ocean acidification and warming on fish growth

When organisms are unable to feed ad libitum they may be more susceptible to negative effects of environmental stressors such as ocean acidification and warming (OAW). We reared sea bass (Dicentrarchus labrax) at 15 or 20 °C and at ambient or high PCO2 (650 versus 1750 µatm PCO2; pH = 8.1 or 7.6) at ad libitum feeding and observed no discernible effect of PCO2 on the size-at-age of juveniles after 277 (20 °C) and 367 (15 °C) days. Feeding trials were then conducted including a restricted ration (25% ad libitum). At 15 °C, growth rate increased with ration but was unaffected by PCO2. At 20 °C, acidification and warming acted antagonistically and low feeding level enhanced PCO2 effects. Differences in growth were not merely a consequence of lower food intake but also linked to changes in digestive efficiency. The specific activity of digestive enzymes (amylase, trypsin, phosphatase alkaline and aminopeptidase N) at 20 °C was lower at the higher PCO2 level. Our study highlights the importance of incorporating restricted feeding into experimental designs examining OAW and suggests that ad libitum feeding used in the majority of the studies to date may not have been suitable to detect impacts of ecological significance.

The Arctic picoeukaryote &amp;lt;i&amp;gt;Micromonas pusilla&amp;lt;/i&amp;gt; benefits from ocean acidification under constant and dynamic light

Abstract. Compared to the rest of the globe, the Arctic Ocean is affected disproportionately by climate change. Despite these fast environmental changes, we currently know little about the effects of ocean acidification (OA) on marine key species in this area. Moreover, the existing studies typically test the effects of OA under constant, hence artificial, light fields. In this study, the abundant Arctic picoeukaryote Micromonas pusilla was acclimated to current (400 µatm) and future (1000 µatm) pCO2 levels under a constant as well as a dynamic light, simulating more realistic light fields as experienced in the upper mixed layer. To describe and understand the responses to these drivers, growth, particulate organic carbon (POC) production, elemental composition, photophysiology and reactive oxygen species (ROS) production were analysed. M. pusilla was able to benefit from OA on various scales, ranging from an increase in growth rates to enhanced photosynthetic capacity, irrespective of the light regime. These beneficial effects were, however, not reflected in the POC production rates, which can be explained by energy partitioning towards cell division rather than biomass build-up. In the dynamic light regime, M. pusilla was able to optimize its photophysiology for effective light usage during both low- and high-light periods. This photoacclimative response, which was achieved by modifications to photosystem II (PSII), imposed high metabolic costs leading to a reduction in growth and POC production rates when compared to constant light. There were no significant interactions observed between dynamic light and OA, indicating that M. pusilla is able to maintain effective photoacclimation without increased photoinactivation under high pCO2. Based on these findings, M. pusilla is likely to cope well with future conditions in the Arctic Ocean.

Carryover effects of temperature and pCO2 across multiple Olympia oyster populations.

Predicting how populations will respond to ocean change across generations is critical to effective conservation of marine species. One emerging factor is the influence of parental exposures on offspring phenotype, known as intergenerational carryover effects. Parental exposure may deliver beneficial or detrimental characteristics to offspring that can influence larval recruitment patterns, thus shaping how populations and community structure respond to ocean change. Impacts of adult exposure to elevated winter temperature and pCO2 on reproduction and offspring viability were examined in the Olympia oyster (Ostrea lurida) using three populations of adult, hatchery-reared O. lurida, plus an additional cohort spawned from one of the populations. Oysters were sequentially exposed to elevated temperature (+4°C, at 10°C), followed by elevated pCO2 (+2,204μatm, at 3,045μatm) during winter months. Male gametes were more developed after elevated temperature exposure and less developed after high pCO2 exposure, but there was no impact on female gametes or sex ratios. Oysters previously exposed to elevated winter temperature released larvae earlier, regardless of pCO2 exposure. Those exposed to elevated winter temperature as a sole treatment released more larvae on a daily basis but, when also exposed to high pCO2 , there was no effect. These combined results indicate that elevated winter temperature accelerates O. lurida spermatogenesis, resulting in earlier larval release and increased production, with elevated pCO2 exposure negating effects of elevated temperature. Altered recruitment patterns may therefore follow warmer winters due to precocious spawning, but these effects may be masked by coincidental high pCO2 . Offspring were reared in common conditions for 1 yr, then deployed for 3 months in four estuarine bays with distinct environmental conditions. Offspring of parents exposed to elevated pCO2 had higher survival rates in two of the four bays. This carryover effect demonstrates that parental conditions can have substantial ecologically relevant impacts that should be considered when predicting impacts of environmental change. Furthermore, Olympia oysters may be more resilient in certain environments when progenitors are pre-conditioned in stressful conditions. Combined with other recent studies, our work suggests that the Olympia may be more equipped than other oysters for the challenge of a changing ocean.

Response of coralline algae Porolithon onkodes to elevated seawater temperature and reduced pH

Coralline algae (CA), a type of primary calcifying producer presented in coastal ecosystems, are considered one of the highly sensitive organisms to marine environmental change. However, experimental studies on coralline algae responses to elevated seawater temperature and reduced pH have documented either contradictory or opposite results. In this study, we analysed the growth and physiological responses of coralline algae Porolithon onkodes to the elevated temperature (30.8°C) and reduced pH (7.8). The aim of this analysis was to observe the direct and combined effects, while elucidating the growth and photosynthesis in this response. It was demonstrated that the algae thallus growth rate and photosynthesis under elevated temperature were depressed by 21.5% and 14.9% respectively. High pCO2 enhanced the growth and photosynthesis of the thallus at ambient temperature, while they were deceased when both temperature and pCO2 were elevated. CA is among the most sensitive organisms to ocean acidification (OA) because of their precipitate high Mg-calcite. We hypothesize that coralline algae could increase their calcification rate in order to counteract the effects of moderate acidification, but offset by the effect of elevated temperature. Accordingly, our results also support the conclusion that global warming (GW) is a stronger threat to algal performance than OA. Our findings are also proposed that coralline algae may be more resilient under OA than GW.

Year-long effects of high pCO2 on the community structure of a tropical fore reef assembled in outdoor flumes

Abstract In this study, fore reef coral communities were exposed to high pCO2 for a year to explore the relationship between net accretion (Gnet) and community structure (planar area growth). Coral reef communities simulating the fore reef at 17-m depth on Mo’orea, French Polynesia, were assembled in three outdoor flumes (each 500 l) that were maintained at ambient (396 µatm), 782 µatm, and 1434 µatm pCO2, supplied with seawater at 300 l h−1, and exposed to light simulating 17-m depth. The communities were constructed using corals from the fore reef, and the responses of massive Porites spp., Acropora spp., and Pocillopora verrucosa were assessed through monthly measurements of Gnet and planar area. High pCO2 depressed Gnet but did not affect colony area by taxon, although the areas of Acropora spp. and P. verrucosa summed to cause multivariate community structure to differ among treatments. These results suggest that skeletal plasticity modulates the effects of reduced Gnet at high pCO2 on planar growth, at least over a year. The low sensitivity of the planar growth of fore reef corals to the effects of ocean acidification (OA) on net calcification supports the counterintuitive conclusion that coral community structure may not be strongly affected by OA.

Cycling phosphorus on the Archean Earth: Part I. Continental weathering and riverine transport of phosphorus

Phosphorus (P) is the key nutrient thought to limit primary productivity on geological timescales. Phosphate levels in Archean marine sediments are low, but quantification of the P cycle and how it changed through a billion years of recorded Archean history remain a challenge, hindering our understanding of the role played by P in biosphere/geosphere co-evolution on the early Earth.Here, we design kinetic and thermodynamic models to quantitatively assess one key component of the early P cycle – continental weathering – by considering the emergence and elevation of continents, as well as the evolution of climate, the atmosphere, and the absence of macroscopic vegetation during the Archean Eon. Our results suggest that the weathering rate of apatite, the major P-hosting mineral in the rocks, was at least five times higher in the Archean Eon than today, attributable to high levels of pCO2,g. Despite this, the weathering flux of P to the oceans was negligible in the early Archean Eon, increasing to a level comparable to or greater than the modern by the end of eon, a consequence of accelerating continental emergence. Furthermore, our thermodynamic calculations indicate high solubilities of primary and secondary P-hosting minerals in the acidic weathering fluids on land, linking to high Archean pCO2,g. Thus, weathering of P was both kinetically and thermodynamically favorable on the Archean Earth, and river water could transport high levels of dissolved P to the oceans, as also supported by the observed P-depletion in our new compilation of Archean paleosols. Lastly, we evaluated the relative rates of physical erosion and chemical weathering of silicates during the Archean Eon. The results suggest that continental weathering on the early and middle Archean Earth might have been transport-limited due to low erosion rates associated with limited subaerial emergence and low plateau elevations; by the late Archean, however, continental weathering would have transited to kinetically-limited state because of continental emergence, increased plateau elevation, and weakening weathering rates. Overall, our weathering calculations together with paleosol evidence indicate an increasing flux of bioavailable P to the oceans through time, associated with late Archean continental emergence, reaching levels comparable to or higher than modern values by the end of the eon. Increased P fluxes could have fueled increasing rates of primary production, including oxygenic photosynthesis, through time, facilitating the irreversible oxidation of the Earth’s atmosphere early in the Proterozoic Eon.

Experimental acidification increases susceptibility of Mercenaria mercenaria to infection by Vibrio species

Ocean acidification alters seawater carbonate chemistry, which can have detrimental impacts for calcifying organisms such as bivalves. This study investigated the physiological cost of resilience to acidification in Mercenaria mercenaria, with a focus on overall immune performance following exposure to Vibrio spp. Larval and juvenile clams reared in seawater with high pCO2 (~1200 ppm) displayed an enhanced susceptibility to bacterial pathogens. Higher susceptibility to infection in clams grown under acidified conditions was derived from a lower immunity to infection more so than an increase in growth of bacteria under high pCO2. A reciprocal transplant of juvenile clams demonstrated the highest mortality amongst animals transplanted from low pCO2/high pH to high pCO2/low pH conditions and then exposed to bacterial pathogens. Collectively, these results suggest that increased pCO2 will result in immunocompromised larvae and juveniles, which could have complex and pernicious effects on hard clam populations.