Posts Tagged 'physiology'

Impact of ocean acidification and warming on the bioenergetics of developing eggs of Atlantic herring Clupea harengus

Atlantic herring (Clupea harengus) is a benthic spawner, therefore its eggs are prone to encounter different water conditions during embryonic development, with bottom waters often depleted of oxygen and enriched in CO2. Some Atlantic herring spawning grounds are predicted to be highly affected by ongoing Ocean Acidification and Warming with water temperature increasing by up to +3°C and CO2 levels reaching ca. 1000 μatm (RCP 8.5). Although many studies investigated the effects of high levels of CO2 on the embryonic development of Atlantic herring, little is known about the combination of temperature and ecologically relevant levels of CO2. In this study, we investigated the effects of Ocean Acidification and Warming on embryonic metabolic and developmental performance such as mitochondrial function, respiration, hatching success (HS) and growth in Atlantic herring from the Oslo Fjord, one of the spawning grounds predicted to be greatly affected by climate change. Fertilized eggs were incubated under combinations of two PCO2 conditions (400 μatm and 1100 μatm) and three temperatures (6, 10 and 14°C), which correspond to current and end-of-the-century conditions. We analysed HS, oxygen consumption (MO2) and mitochondrial function of embryos as well as larval length at hatch. The capacity of the electron transport system (ETS) increased with temperature, reaching a plateau at 14°C, where the contribution of Complex I to the ETS declined in favour of Complex II. This relative shift was coupled with a dramatic increase in MO2 at 14°C. HS was high under ambient spawning conditions (6–10°C), but decreased at 14°C and hatched larvae at this temperature were smaller. Elevated PCO2 increased larval malformations, indicating sub-lethal effects. These results indicate that energetic limitations due to thermally affected mitochondria and higher energy demand for maintenance occur at the expense of embryonic development and growth.

Continue reading ‘Impact of ocean acidification and warming on the bioenergetics of developing eggs of Atlantic herring Clupea harengus’

Possible roles of glutamine synthetase in responding to environmental changes in a scleractinian coral

Glutamine synthetase is an enzyme that plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. In this study, the activity and responses of glutamine synthetase towards environmental changes were investigated in the scleractinian coral Pocillopora damicornis. The identified glutamine synthetase (PdGS) was comprised of 362 amino acids and predicted to contain one Gln-synt_N and one Gln-synt_C domain. Expression of PdGS mRNA increased significantly after 12 h (1.28-fold, p < 0.05) of exposure to elevated ammonium, while glutamine synthetase activity increased significantly from 12 to 24 h, peaking at 12 h (54.80 U mg−1, p < 0.05). The recombinant protein of the mature PdGS (rPdGS) was expressed in E. coli BL21, and its activities were detected under different temperature, pH and glufosinate levels. The highest levels of rPdGS activity were observed at 25 °C and pH 8 respectively, but decreased significantly at lower temperature, and higher or lower pH. Furthermore, the level of rPdGS activities was negatively correlated with the concentration of glufosinate, specifically decreasing at 10−5 mol L−1 glufosinate to be less than 50% (p < 0.05) of that in the blank. These results collectively suggest that PdGS, as a homologue of glutamine synthetase, was involved in the nitrogen assimilation in the scleractinian coral. Further, its physiological functions could be suppressed by high temperature, ocean acidification and residual glufosinate, which might further regulate the coral-zooxanthella symbiosis via the nitrogen metabolism in the scleractinian coral P. damicornis.

Continue reading ‘Possible roles of glutamine synthetase in responding to environmental changes in a scleractinian coral’

Projected amplification of food web bioaccumulation of MeHg and PCBs under climate change in the Northeastern Pacific

Climate change increases exposure and bioaccumulation of pollutants in marine organisms, posing substantial ecophysiological and ecotoxicological risks. Here, we applied a trophodynamic ecosystem model to examine the bioaccumulation of organic mercury (MeHg) and polychlorinated biphenyls (PCBs) in a Northeastern Pacific marine food web under climate change. We found largely heterogeneous sensitivity in climate-pollution impacts between chemicals and trophic groups. Concentration of MeHg and PCBs in top predators, including resident killer whales, is projected to be amplified by 8 and 3%, respectively, by 2100 under a high carbon emission scenario (Representative Concentration Pathway 8.5) relative to a no-climate change control scenario. However, the level of amplification increases with higher carbon emission scenario for MeHg, but decreases for PCBs. Such idiosyncratic responses are shaped by the differences in bioaccumulation pathways between MeHg and PCBs, and the modifications of food web dynamics between different levels of climate change. Climate-induced pollutant amplification in mid-trophic level predators (Chinook salmon) are projected to be higher (~10%) than killer whales. Overall, the predicted trophic magnification factor is ten-fold higher in MeHg than in PCBs under high CO2 emissions. This contribution highlights the importance of understanding the interactions with anthropogenic organic pollutants in assessing climate risks on marine ecosystems.

Continue reading ‘Projected amplification of food web bioaccumulation of MeHg and PCBs under climate change in the Northeastern Pacific’

The acute transcriptomic response of coral-algae interactions to pH fluctuation

Little is known about how the coral host and its endosymbiont interactions change when they are exposed to a sudden nonlinear environmental transformation, yet this is crucial to coral survival in extreme events. Here, we present a study that investigates the transcriptomic response of corals and their endosymbionts to an abrupt change in pH (pH 7.60 and 8.35). The transcriptome indicates that the endosymbiont demonstrates a synchronized downregulation in carbon acquisition and fixation processes and may result in photosynthetic dysfunction in endosymbiotic Symbiodinium, suggesting that the mutualistic continuum of coral–algae interactions is compromised in response to high-CO2 exposure. Transcriptomic data also shows that corals are still capable of calcifying in response to the low pH but could experience a series of negative effects on their energy dynamics, which including protein damage, DNA repair, ion transport, cellular apoptosis, calcification acclimation and maintenance of intracellular pH homeostasis and stress tolerance to pH swing. This suggests enhanced energy costs for coral metabolic adaptation. This study provides a deeper understanding of the biological basis related to the symbiotic corals in response to extreme future climate change and environmental variability.

Continue reading ‘The acute transcriptomic response of coral-algae interactions to pH fluctuation’

Effects of CO2 enrichment on two microalgae species: a toxicity approach using consecutive generations

Highlights

• The paper addresses the potential impacts of CO2 enrichment in the marine environment.
• Two different marine microalgae species were used through four consecutive generations.
• T. chuii showed a slight adaptation through generations, in terms of metabolic activity.
• P. tricornutum was the most sensitive one with almost total growth inhibition in the fourth generation.
• The results give valuable data about the transgenerational effects of CO2 enrichment on microalgae.

Abstract

As a result of the increasing pressure provoked by anthropogenic activities, the world climate is changing and oceans health is in danger. One of the most important factors affecting the marine environment is the well-known process called ocean acidification. Also, there are other natural or anthropogenic processes that produce an enrichment of CO2 in the marine environment (CO2 leakages from Carbon Capture and Storage technologies (CCS), organic matter diagenesis, volcanic vents, etc). Most of the studies related to acidification of the marine environment by enrichment of CO2 have been focused on short-term experiments. To evaluate the effects related to CO2 enrichment, laboratory-scale experiments were performed using the marine microalgae Tetraselmis chuii and Phaeodactylum tricornutum. Three different pH values (two treatments – pH 7.4 and 6.0 – and a control – pH 8.0) were tested on the selected species across four consecutive generations. Seawater was collected and exposed to different scenarios of CO2 enrichment by means of CO2 injection. The results showed different effects depending on the species and the generation used. Effects on T. chuii were shown on cell density, chlorophyll-a and metabolic activity, however, a slight adaptation across generations was found in this last parameter. P. tricornutum was more sensitive to acidification conditions through generations, with practically total growth inhibition in the fourth one. The conclusions obtained in this work are useful to address the potential ecological risk related to acidification by enrichment of CO2 on the marine ecosystem by using consecutive generations of microalgae.

Continue reading ‘Effects of CO2 enrichment on two microalgae species: a toxicity approach using consecutive generations’

The effect of ocean acidification on tropical coral calcification: insights from calcification fluid DIC chemistry

Highlights

• Calcification fluid pH and [co-precipitating DIC] are positively correlated in all corals.
• [Precipitating DIC] and coral calcification rate are positively correlated in all but one outlier coral.
• Corals cultured at high seawater pCO2 usually have low fluid pH and [precipitating DIC]. Reduced DIC substrate at the calcification site is the likely cause of decreased coral calcification rates under ocean acidification scenarios.
• The outlier coral maintained a high calcification fluid pH and [co-precipitating DIC] at high seawater pCO2 but exhibited a low calcification rate suggesting that corals have a limited energy budget for calcification which is apportioned between proton extrusion from the calcification site and other processes e.g. synthesis of the skeletal organic matrix.

Abstract

Ocean acidification typically reduces calcification in tropical marine corals but the mechanism for this process is not understood. We use skeletal boron geochemistry (B/Ca and δ11B) to reconstruct the calcification fluid DIC of corals cultured over both high and low seawater pCO2 (180, 400 and 750 μatm). We observe strong positive correlations between calcification fluid pH and concentrations of the DIC species potentially implicated in aragonite precipitation (be they CO32−, HCO3 or HCO3 + CO32−). Similarly, with the exception of one outlier, the fluid concentrations of precipitating DIC species are strongly positively correlated with coral calcification rate. Corals cultured at high seawater pCO2 usually have low calcification fluid pH and low concentrations of precipitating DIC, suggesting that a reduction in DIC substrate at the calcification site is responsible for decreased calcification. The outlier coral maintained high pHCF and DICCF at high seawater pCO2 but exhibited a reduced calcification rate indicating that the coral has a limited energy budget to support proton extrusion from the calcification fluid and meet other calcification demands. We find no evidence that increasing seawater pCO2 enhances diffusion of CO2 into the calcification site. Instead the overlying [CO2] available to diffuse into the calcification site appears broadly comparable between seawater pCO2 treatments, implying that metabolic activity (respiration and photosynthesis) generates a similar [CO2] in the vicinity of the calcification site regardless of seawater pCO2.

Continue reading ‘The effect of ocean acidification on tropical coral calcification: insights from calcification fluid DIC chemistry’

Interactive effects of ocean acidification and ocean warming on Pacific herring (Clupea pallasi) early life stages

The synergy of ocean acidification and ocean warming may lead to negative effects in  marine organism responses that would be absent under single stressors. While adult fish are  effective acid-base regulators, early life stages may be more susceptible to environmental  stressors. Pacific herring are ecologically and economically important forage fish native to the  U.S. Pacific Northwest (PNW), and several herring populations in the PNW have experienced reductions in stock abundance. Studies to date have focused on Atlantic herring, and little is  known about the response of Pacific herring to ocean acidification and warming. Therefore, this  study focused on the combined effects of ocean acidification and warming on Pacific herring early life stages. We incubated Pacific herring embryos under a factorial design of two  temperature (10°C, 16°C) and two pCO2 (600 µatm, 1200 µatm) treatments from fertilization  until hatch (11 to 15 days depending on temperature). Elevated pCO2 was associated with a small increase in embryo mortality. However, elevated temperature was associated with greater  embryo mortality, greater embryo heart rates and yolk areas upon hatch, lower percent normal hatch, and decreased larval lengths. The interaction of elevated temperature and pCO2 was associated greater embryo respiration rates and yolk areas. This study indicates that temperature will likely be the primary global change stressor affecting Pacific herring embryology, and interactive effects with pCO2 may introduce additional challenges.
Continue reading ‘Interactive effects of ocean acidification and ocean warming on Pacific herring (Clupea pallasi) early life stages’


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