Query: pco2 acidification

title: The physiological response of marine diatoms to ocean acidification: differential roles of seawater pCO2 and pH
abstract: Although increasing the pCO2 for diatoms will presumably down regulate the CO2 concentrating mechanism (CCM) to save energy for growth, different species have been reported to respond differently to ocean acidification (OA) To better understand their growth responses to OA, we acclimated the diatoms Thalassiosira pseudonana, Phaeodactylum tricornutum, and Chaetoceros muelleri to ambient (pCO2 400 matm, pH 8.1) carbonated (pCO2 800 matm, pH 8.1) acidified (pCO2 400 matm, pH 7.8) and OA (pCO2 800 matm, pH 7.8) conditions and investigated how seawater pCO2 and pH affect their CCMs, photosynthesis, and respiration both individually and jointly. In all three diatoms, carbonation down regulated the CCMs, while acidification increased both the photosynthetic carbon fixation rate and the fraction of CO2 as the inorganic carbon source. The positive OA effect on photosynthetic carbon fixation was more pronounced in C. muelleri, which had a relatively lower photosynthetic affinity for CO2, than in either T. pseudonana or P. tricornutum. In response to OA, T. pseudonana increased respiration for active disposal of H+ to maintain its intracellular pH, whereas P. tricornutum and C. muelleri retained their respiration rate but lowered the intracellular pH to maintain the cross membrane electrochemical gradient for H+ efflux. As the net result of changes in photosynthesis and respiration, growth enhancement to OA of the three diatoms followed the order of C. muelleri P. tricornutum T. pseudonana. This study demonstrates that elucidating the separate and joint impacts of increased pCO2 and decreased pH aids the mechanistic understanding of OA effects on diatoms in the future, acidified oceans.

title: Diurnally Fluctuating pCO2 Modifies the Physiological Responses of Coral Recruits Under Ocean Acidification
abstract: Diurnal pCO2 fluctuations have the potential to modulate the biological impact of ocean acidification (OA) on reef calcifiers, yet little is known about the physiological and biochemical responses of scleractinian corals to fluctuating carbonate chemistry under OA. Here, we exposed newly settled Pocillopora damicornis for 7 days to ambient pCO2, steady and elevated pCO2 (stable OA) and diurnally fluctuating pCO2 under future OA scenario (fluctuating OA) We measured the photo physiology, growth (lateral growth, budding and calcification) oxidative stress and activities of carbonic anhydrase (CA) Ca ATPase and Mg ATPase. Results showed that while OA enhanced the photochemical performance of in hospite symbionts, it also increased catalase activity and lipid peroxidation. Furthermore, both OA treatments altered the activities of host and symbiont CA, suggesting functional changes in the uptake of dissolved inorganic carbon (DIC) for photosynthesis and calcification. Most importantly, only the fluctuating OA treatment resulted in a slight drop in calcification with concurrent up regulation of Ca ATPase and Mg ATPase, implying increased energy expenditure on calcification. Consequently, asexual budding rates decreased by 50% under fluctuating OA. These results suggest that diel pCO2 oscillations could modify the physiological responses and potentially alter the energy budget of coral recruits under future OA, and that fluctuating OA is more energetically expensive for the maintenance of coral recruits than stable OA.

title: Transgenerational Effects of pCO2 Driven Ocean Acidification on Adult Mussels Mytilus chilensis Modulate Physiological Response to Multiple Stressors in Larvae
abstract: The effect of CO2 driven ocean acidification (OA) on marine biota has been extensively studied mostly on a single stage of the life cycle. However, the cumulative and population level response to this global stressor may be biased due to transgenerational effects and their impacts on physiological plasticity. In this study, we exposed adult mussels Mytilus chilensis undergoing gametogenesis to two pCO2 levels (550 and 1200 matm) for 16 weeks, aiming to understand if prolonged exposure of reproductive individuals to OA can affect the performance of their offspring, which, in turn, were reared under multiple stressors (pCO2, temperature, and dissolved cadmium) Our results indicate dependence between the level of pCO2 of the broodstock (i.e. parental effect) and the performance of larval stages in terms of growth and physiological rates, as a single effect of temperature. While main effects of pCO2 and cadmium were observed for larval growth and ingestion rates, respectively, the combined exposure to stressors had antagonistic effects. Moreover, we found a suppression of feeding activity in post spawning broodstock upon high pCO2 conditions. Nevertheless, this observation was not reflected in the final weight of the broodstock and oocyte diameter. Due to the ecological and socioeconomic importance of mussels' species around the globe, the potential implications of maternal effects for the physiology, survival, and recruitment of larvae under combined global change stressors warrant further investigation.

title: Effects of ocean acidification with pCO2 diurnal fluctuations on survival and larval shell formation of Ezo abalone, Haliotis discus hannai.
abstract: This study assessed the effects of constant and diurnally fluctuating pCO2 on development and shell formation of larval abalone Haliotis discus hannai. The larvae was exposed to different pCO2 conditions; constant [450, 800, or 1200 matm in the first experiment (Exp. I) 450 or 780 matm in the second experiment (Exp. II) or diurnally fluctuating pCO2 (800 400 or 1200 400 matm in Exp. I, 450 80, 780 200 or 780 400 matm in Exp. II) Mortality, malformation rates or shell length of larval abalone were not significantly different among the 450, 800, and 800 400 matm pCO2 treatments. Meanwhile, significantly higher malformation rates and smaller shells were detected in the 1200 and 1200 400 matm pCO2 treatments than in the 450 matm pCO2 treatment. The negative impacts were greater in the 1200 400 matm than in the 1200 matm. Shell length and malformation rate of larval abalone were related with aragonite saturation state (O aragonite) in experimental seawater, and greatly changed around 1.1 of O aragonite which corresponded to 1000 1300 matm pCO2. These results indicate that there is a pCO2 threshold associated with O aragonite in the seawater, and that pCO2 fluctuations produce additional negative impacts on abalone when above the threshold. Clear relationships were detected between abalone fitness and the integrated pCO2 value over the threshold, indicating that the effects of OA on development and shell formation of larval abalone can be determined by intensity and time of exposure to pCO2 over the threshold.

title: Early life stages of the Arctic copepod Calanus glacialis are unaffected by increased seawater pCO2: Towards a Broader Perspective on Ocean Acidification Research Part 2 A special issue of the ICES Journal of Marine Science
abstract: &NA; As the world's oceans continue to absorb anthropogenic CO2 from the atmosphere, the carbonate chemistry of seawater will change. This process, termed ocean acidification, may affect the physiology of marine organisms. Arctic seas are expected to experience the greatest decreases in pH in the future, as changing sea ice dynamics and naturally cold, brackish water, will accelerate ocean acidification. In this study, we investigated the effect of increased pCO2 on the early developmental stages of the key Arctic copepod Calanus glacialis. Eggs from wild caught C. glacialis females from Svalbard, Norway (80degN) were cultured for 2 months to copepodite stage C1 in 2degC seawater under four pCO2 treatments (320, 530, 800, and 1700 &mgr;atm) Developmental rate, dry weight, and carbon and nitrogen mass were measured every other day throughout the experiment, and oxygen consumption rate was measured at stages N3, N6, and C1. All endpoints were unaffected by pCO2 levels projected for the year 2300. These results indicate that naupliar development in wild populations of C. glacialis is unlikely to be detrimentally affected in a future high CO2 ocean.

title: Effects of pCO2 on photosynthesis and respiration of tropical scleractinian corals and calcified algae: Towards a Broader Perspective on Ocean Acidification Research Part 2 A special issue of the ICES Journal of Marine Science
abstract: &NA; The effects of ocean acidification (OA) on coral reefs have been studied thoroughly with a focus on the response of calcification of corals and calcified algae. However, there are still large gaps in our knowledge of the effects of OA on photosynthesis and respiration of these organisms. Comparisons among species and determination of the functional relationships between pCO2 and either photosynthesis or respiration are difficult using previously published data, because experimental conditions typically vary widely between studies. Here, we tested the response of net photosynthesis, gross photosynthesis, dark respiration, and light enhanced dark respiration (LEDR) of eight coral taxa and seven calcified alga taxa to six different pCO2 levels (from 280 to 2000 &mgr;atm) Organisms were maintained during 7 10 days incubations in identical conditions of light, temperature, and pCO2 to facilitate comparisons among species. Net photosynthesis was not affected by pCO2 in seven of eight corals or any of the algae; gross photosynthesis did not respond to pCO2 in six coral taxa and six algal taxa; dark respiration also was unaffected by pCO2 in six coral and six algae; and LEDR did not respond to pCO2 in any of the tested species. Overall, our results show that pCO2 levels up to 2000 &mgr;atm likely will not fertilize photosynthesis or modify respiration rates of most of the main calcifiers on the back reef of Moorea, French Polynesia.

title: Combined effects of elevated pCO2, temperature, and starvation stress on larvae of a large tropical marine fish: Towards a Broader Perspective on Ocean Acidification Research Part 2 A special issue of the ICES Journal of Marine Science
abstract: &NA; Ocean acidification and other environmental changes pose an ecological challenge to marine organisms globally. Although the youngest life stages of these organism are likely to be most affected, a limited number of studies of larval fishes have investigated the effects of combined stressors. We conducted two experiments on larval cobia (Rachycentron canadum) raised under combinations of elevated pCO2 and increased temperature or starvation stress. Larvae responded to individual CO2, temperature, and rationing treatments, and there was a negative effect of elevated pCO2 on starvation resistance, but few synergistic effects of combined stressors. Elevated pCO2 (1700 2100 &mgr;atm pCO2) caused a transient but significant reduction in larval standard length (SL) growth rate, and development rate, while warmer temperature (32 vs. 27 degC) caused a consistent increase in SL, development rate, and swimming ability. Larval condition (RNA:DNA ratio) was unaffected by elevated pCO2 although larvae fed a 25% ration had significantly reduced SL, growth rate, and development rate. Under complete feeding cessation, larvae in elevated pCO2 seawater demonstrated lower starvation resistance, indicating that acidification may increase starvation risk in a patchy marine environment. Overall, our results indicate that larval cobia are resistant to any major direct impact of combined elevated pCO2 and temperature or rationing stress.

title: The early life stages of an estuarine fish, the red drum (Sciaenops ocellatus) are tolerant to high pCO2: Towards a Broader Perspective on Ocean Acidification Research Part 2 A special issue of the ICES Journal of Marine Science
abstract: &NA; Ocean acidification (OA) and other climate change induced environmental alterations are resulting in unprecedented rates of environmental deterioration. This environmental change is generally thought to be too fast for adaptation using typical evolutionary processes, and thus sensitivity may be dependent on the presence of existing tolerant genotypes and species. Estuaries undergo natural pCO2 fluctuations over a variety of time scales, and levels regularly exceed the predicted end of the century values. Interestingly, estuarine fish species have been overlooked in reference to the impacts of OA. Here, we use the estuarine red drum (Sciaenops ocellatus) as a model to explore the hypothesis that early life stages of estuarine species have intrinsic tolerance to elevated pCO2. Our sensitivity endpoints included: survival, growth, yolk consumption, heart rate, and scototaxis. Survival was significantly decreased when exposed to 1300 &mgr;atm and 3000 &mgr;atm, and coincided with a significant increase in heart rate at the 3000 &mgr;atm exposure. However, these effects were less pronounced than the findings of previous studies on other marine fish species. Yolk depletion rate and standard length were not significantly affected by pCO2. Scototaxis behaviour was also not significantly affected by exposure to elevated levels of pCO2 under both acute and acclimated exposure scenarios. Overall, these results support the hypothesis that estuarine life history and habitat usage may play a critical role in determining sensitivity of fish species to OA. Furthermore, estuarine species may provide present day insight into the physiological and ecological foundation of OA tolerance.

title: Linking rising pCO2 and temperature to the larval development and physiology of the American lobster (Homarus americanus) Towards a Broader Perspective on Ocean Acidification Research Part 2 A special issue of the ICES Journal of Marine Science
abstract: &NA; Few studies have evaluated the joint effects of elevated temperature and pCO2 on marine organisms. In this study we investigated the interactive effects of Intergovernmental Panel on Climate Change predicted temperature and pCO2 for the end of the 21st century on key aspects of larval development of the American lobster, Homarus americanus, an otherwise well studied, iconic, and commercially prominent species in the northeastern United States and Atlantic Canada. Our experiments showed that larvae (stages I III) and postlarvae (stage IV) reared in the high temperature treatments (19 degC) experienced significantly lower survival, developed twice as fast, and had significantly higher oxygen consumption rates, than those in ambient treatments (16 degC) Larvae from the ambient temperature/high pCO2 (750 ppm) treatment had significantly longer carapace lengths, greater dry masses in stages I III and higher C: N ratios in stage IV than larvae from all other treatments. Stage IVs raised in the high pCO2 treatment at 19 degC had significantly higher feeding rates and swimming speeds than stage IVs from the other three treatments. Together these results suggest that projected end century warming will have greater adverse effects than increased pCO2 on larval survival, and changing pCO2 may have a complex effect on larval metabolism and behaviour. Understanding how the most vulnerable life stages of the lobster life cycle respond to climate change is essential in connecting the northward geographic shifts projected by habitat quality models, and the underlying physiological and genetic mechanisms that drive their ecology.

title: Long term exposure to elevated pCO2 more than warming modifies early life shell growth in a temperate gastropod: Towards a Broader Perspective on Ocean Acidification Research Part 2 A special issue of the ICES Journal of Marine Science
abstract: &NA; Co occurring global change drivers, such as ocean warming and acidification, can have large impacts on the behaviour, physiology, and health of marine organisms. However, whilst early life stages are thought to be most sensitive to these impacts, little is known about the individual level processes by which such impacts take place. Here, using mesocosm experiments simulating ocean warming (OW) and ocean acidification (OA) conditions expected for the NE Atlantic region by 2100 using a variety of treatments of elevated pCO2 and temperature. We investigated their impacts on bio mineralization, microstructure, and ontogeny of Nucella lapillus (L. juveniles, a common gastropod predator that exerts important top down controls on biodiversity patterns in temperate rocky shores. The shell of juveniles hatched in mesocosms during a 14 month long experiment were analysed using micro CT scanning, 3D geometric morphometrics, and scanning electron microscopy. Elevated temperature and age determined shell density, length, width, thickness, elemental chemistry, shape, and shell surface damages. However, co occurring elevated pCO2 modified the impacts of elevated temperature, in line with expected changes in carbonate chemistry driven by temperature. Young N. lapillus from acidified treatments had weaker shells and were therefore expected to be more vulnerable to predation and environmental pressures such as wave action. However, in some instances, the effects of both higher CO2 content and elevated temperature appeared to have reversed as the individuals aged. This study suggests that compensatory development may therefore occur, and that expected increases in juvenile mortality under OA and OW may be counteracted, to some degree, by high plasticity in shell formation in this species. This feature may prove advantageous for N. lapillus community dynamics in near future conditions.