In the present study, we depict the structural modification of test minerals, physiological response and ovarian damage in the tropical sea urchin Salmacis virgulata using microcosm CO2 (Carbon dioxide) perturbation experiment. S. virgulata were exposed to hypercapnic conditions with four different pH levels using CO2 gas bubbling method that reflects ambient level (pH 8.2) and elevated pCO2 scenarios (pH 8.0, 7.8 and 7.6). The variations in physical strength and mechanical properties of S. virgulata test were evaluated by thermogravimetric analysis, Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanned electron microscopy analysis. Biomarker enzymes such as glutathione-S-transferase, catalase, acetylcholine esterase, lipid peroxidase and reduced glutathione showed physiological stress and highly significant (p < 0.01) towards pH 7.6 and 7.8 treatments. Ovarian cells were highly damaged at pH 7.6 and 7.8 treatments. This study proved that the pH level 7.6 and 7.8 drastically affect calcification, physiological response and ovarian cells in S. virgulata.
Continue reading ‘Effect of CO2 driven ocean acidification on calcification, physiology and ovarian cells of tropical sea urchin Salmacis virgulata – a microcosm approach’Posts Tagged 'laboratory'
Effect of CO2 driven ocean acidification on calcification, physiology and ovarian cells of tropical sea urchin Salmacis virgulata – a microcosm approach
Published 25 January 2021 Science ClosedTags: biological response, calcification, echinoderms, Indian, laboratory, physiology, reproduction
Impacts of acclimation in warm-low pH conditions on the physiology of the sea urchin Heliocidaris erythrogramma and carryover effects for juvenile offspring
Published 25 January 2021 Science ClosedTags: biological response, echinoderms, laboratory, mortality, multiple factors, performance, physiology, reproduction, South Pacific, temperature
Ocean warming (OW) and acidification (OA) affects nearly all aspects of marine organism physiology and it is important to consider both stressors when predicting responses to climate change. We investigated the effects of long-term exposure to OW and OA on the physiology of adults of the sea urchin, Heliocidaris erythrogramma, a species resident in the southeast Australia warming hotspot. The urchins were slowly introduced to stressor conditions in the laboratory over a 7-week adjustment period to three temperature (ambient, +2°C, +3°C) and two pH (ambient: pHT 8.0; −0.4 units: pHT 7.6) treatments. They were then maintained in a natural pattern of seasonal temperature and photoperiod change, and fixed pH, for 22 weeks. Survival was monitored through week 22 and metabolic rate was measured at 4 and 12 weeks of acclimation, feeding rate and ammonia excretion rate at 12 weeks and assimilation efficiency at 13 weeks. Acclimation to +3°C was deleterious regardless of pH. Mortality from week 6 indicated that recent marine heatwaves are likely to have been deleterious to this species. Acclimation to +2°C did not affect survival. Increased temperature decreased feeding and increased excretion rates, with no effect of acidification. While metabolic rate increased additively with temperature and low pH at week 4, there was no difference between treatments at week 12, indicating physiological acclimation in surviving urchins to stressful conditions. Regardless of treatment, H. erythrogramma had a net positive energy budget indicating that the responses were not due to energy limitation. To test for the effect of parental acclimation on offspring responses, the offspring of acclimated urchins were reared to the juvenile stage in OW and OA conditions. Parental acclimation to warming, but not acidification altered juvenile physiology with an increase in metabolic rate. Our results show that incorporation of gradual seasonal environmental change in long-term acclimation can influence outcomes, an important consideration in predicting the consequences of changing climate for marine species.
Continue reading ‘Impacts of acclimation in warm-low pH conditions on the physiology of the sea urchin Heliocidaris erythrogramma and carryover effects for juvenile offspring’Short-term response of flat tree oyster, Isognomon alatus to CO2 acidified seawater in laboratory and field experiments
Published 25 January 2021 Science ClosedTags: biological response, field, laboratory, mollusks, morphology, North Atlantic
Seawater changing chemistry has consequences on coastal ecosystems and their living resources. Future projections suggest the pH could drop ~0.2-0.3 pH units by the year 2100 under a business-as-usual (BAU) CO2 emission scenario. Marine calcifying organisms such as corals, calcifying algae, crustaceans, mussels, oysters and clams are most likely to be impacted by ocean acidification. The Isognomon alatus (flat tree oyster) is an important species that can be negatively affected by the lowering of seawater pH. Isognomon alatus is an important food source, a substrate for other benthic organisms (e.g., stone crab, Menippe mercenaria) and contribute to nutrients recycling in coastal ecosystems. The study was conducted to test the impacts acidified seawater CO2 on the growth of I. alatus under controlled laboratory conditions as well as field experiment. The Isognomon alatus lost weight and experienced negative growth rates of –0.56 ± 0.36 mg g-1day-1 under average pH values of 7.8 expected by the end of this century compared to a loss of –0.26 ± 0.23 mg g-1day-1 under ambient pH (value 8.1) conditions. In contrast, I. alatus incubated in a field experiment showed a gain in weight and positive growth of 3.30 ± 0.23 mg g-1day-1 despite exposure to pH levels (~7.4) during low tide significantly lower than those experienced in the laboratory. Overall, the results showed concern on the impacts of acidification flat tree oyster (Bivalvia:Isognomonidae). A decline of calcifying bivalves populations can impact coastal ecosystems function and indirectly affect the human beings that depend on them as a food source.
Continue reading ‘Short-term response of flat tree oyster, Isognomon alatus to CO2 acidified seawater in laboratory and field experiments’Coccolithophore calcification studied by single-cell impedance cytometry: towards single-cell PIC:POC measurements
Published 22 January 2021 Science ClosedTags: dissolution, laboratory, methods, phytoplankton
Since the industrial revolution 30% of the anthropogenic CO2 is absorbed by oceans, resulting in ocean acidification, which is a threat to calcifying algae. As a result, there has been profound interest in the study of calcifying algae, because of their important role in the global carbon cycle. The coccolithophore Emiliania huxleyi is considered to be globally the most dominant calcifying algal species, which creates a unique exoskeleton from inorganic calcium carbonate platelets. The PIC (particulate inorganic carbon): POC (particulate organic carbon) ratio describes the relative amount of inorganic carbon in the algae and is a critical parameter in the ocean carbon cycle.
In this research we explore the use of microfluidic single-cell impedance spectroscopy in the field of calcifying algae. Microfluidic impedance spectroscopy enables us to characterize single-cell electrical properties in a noninvasive and label-free way. We use the ratio of the impedance at high frequency vs. low frequency, known as opacity, to discriminate between calcified coccolithophores and coccolithophores with a calcite exoskeleton dissolved by acidification (decalcified).
We have demonstrated that using opacity we can discriminate between calcified and decalcified coccolithophores with an accuracy of 94.1%. We have observed a correlation between the measured opacity and the cell height in the channel, which is supported by FEM simulations. The difference in cell density between calcified and decalcified cells can explain the difference in cell height and therefore the measured opacity.
Continue reading ‘Coccolithophore calcification studied by single-cell impedance cytometry: towards single-cell PIC:POC measurements’Sea‐ice microbial communities in the Central Arctic Ocean: limited responses to short‐term pCO2 perturbations
Published 21 January 2021 Science ClosedTags: Arctic, biological response, BRcommunity, chemistry, community composition, laboratory, molecular biology, otherprocess, photosynthesis, prokaryotes
The Arctic Ocean is more susceptible to ocean acidification than other marine environments due to its weaker buffering capacity, while its cold surface water with relatively low salinity promotes atmospheric CO2 uptake. We studied how sea‐ice microbial communities in the central Arctic Ocean may be affected by changes in the carbonate system expected as a consequence of ocean acidification. In a series of four experiments during late summer 2018 aboard the icebreaker Oden, we addressed microbial growth, production of dissolved organic carbon (DOC) and extracellular polymeric substances (EPS), photosynthetic activity, and bacterial assemblage structure as sea‐ice microbial communities were exposed to elevated partial pressures of CO2 (pCO2). We incubated intact, bottom ice‐core sections and dislodged, under‐ice algal aggregates (dominated by Melosira arctica) in separate experiments under approximately 400, 650, 1000, and 2000 μatm pCO2 for 10 d under different nutrient regimes. The results indicate that the growth of sea‐ice algae and bacteria was unaffected by these higher pCO2 levels, and concentrations of DOC and EPS were unaffected by a shifted inorganic C/N balance, resulting from the CO2 enrichment. These central Arctic sea‐ice microbial communities thus appear to be largely insensitive to short‐term pCO2 perturbations. Given the natural, seasonally driven fluctuations in the carbonate system of sea ice, its resident microorganisms may be sufficiently tolerant of large variations in pCO2 and thus less vulnerable than pelagic communities to the impacts of ocean acidification, increasing the ecological importance of sea‐ice microorganisms even as the loss of Arctic sea ice continues.
Continue reading ‘Sea‐ice microbial communities in the Central Arctic Ocean: limited responses to short‐term pCO2 perturbations’Climate change alters the haemolymph microbiome of oysters
Published 21 January 2021 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mollusks, multiple factors, otherprocess, physiology, prokaryotes, South Pacific, temperature
Highlights
- Elevated pCO2 and temperature caused shifts in the oyster haemolymph microbiome.
- Elevated pCO2 was the strongest driver of species diversity and richness.
- Elevated pCO2 and temperature caused a loss of “core” bacteria.
- There was no evidence for a shift in the microbiome from a mutualistic to pathogenic state.
Abstract
The wellbeing of marine organisms is connected to their microbiome. Oysters are a vital food source and provide ecological services, yet little is known about how climate change such as ocean acidification and warming will affect their microbiome. We exposed the Sydney rock oyster, Saccostrea glomerata, to orthogonal combinations of temperature (24, 28 °C) and pCO2 (400 and 1000 μatm) for eight weeks and used amplicon sequencing of the 16S rRNA (V3-V4) gene to characterise the bacterial community in haemolymph. Overall, elevated pCO2 and temperature interacted to alter the microbiome of oysters, with a clear partitioning of treatments in CAP ordinations. Elevated pCO2 was the strongest driver of species diversity and richness and elevated temperature also increased species richness. Climate change, both ocean acidification and warming, will alter the microbiome of S. glomerata which may increase the susceptibility of oysters to disease.
Continue reading ‘Climate change alters the haemolymph microbiome of oysters’Acclimation and adaptation to elevated pCO2 increase arsenic resilience in marine diatoms
Published 19 January 2021 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, mollusks, otherprocess, physiology, phytoplankton
Arsenic pollution is a widespread threat to marine life, but the ongoing rise pCO2 levels is predicted to decrease bio-toxicity of arsenic. However, the effects of arsenic toxicity on marine primary producers under elevated pCO2 are not well characterized. Here, we studied the effects of arsenic toxicity in three globally distributed diatom species (Phaeodactylum tricornutum, Thalassiosira pseudonana, and Chaetoceros mulleri) after short-term acclimation (ST, 30 days), medium-term exposure (MT, 750 days), and long-term (LT, 1460 days) selection under ambient (400 µatm) and elevated (1000 and 2000 µatm) pCO2. We found that elevated pCO2 alleviated arsenic toxicity even after short acclimation times but the magnitude of the response decreased after mid and long-term adaptation. When fed with these elevated pCO2 selected diatoms, the scallop Patinopecten yessoensis had significantly lower arsenic content (3.26–52.83%). Transcriptomic and biochemical analysis indicated that the diatoms rapidly developed arsenic detoxification strategies, which included upregulation of transporters associated with shuttling harmful compounds out of the cell to reduce arsenic accumulation, and upregulation of proteins involved in synthesizing glutathione (GSH) to chelate intracellular arsenic to reduce arsenic toxicity. Thus, our results will expand our knowledge to fully understand the ecological risk of trace metal pollution under increasing human activity induced ocean acidification.
Continue reading ‘Acclimation and adaptation to elevated pCO2 increase arsenic resilience in marine diatoms’Ocean acidification interacts with growth light to suppress CO2 acquisition efficiency and enhance mitochondrial respiration in a coastal diatom
Published 15 January 2021 Science ClosedTags: biological response, growth, laboratory, light, multiple factors, photosynthesis, physiology, phytoplankton, respiration
Highlights
- Ocean acidification (OA) enhances growth of Thalassiosira weissflogii only at limiting low light levels.
- The energy saved from down-regulation of CCMs under OA rather than “CO2 fertilization aids in the enhancement under low levels of light energy supply.
- Coastal diatoms can benefit from OA, especially under cloudy weather or conditions of low solar exposures.
Abstract
Diatom responses to ocean acidification have been documented with variable and controversial results. We grew the coastal diatom Thalassiosira weissflogii under 410 (LC, pH 8.13) vs 1000 μatm (HC, pH 7.83) pCO2 and at different levels of light (80, 140, 220 μmol photons m−2 s−1), and found that light level alters physiological responses to OA. CO2 concentrating mechanisms (CCMs) were down-regulated in the HC-grown cells across all the light levels, as reflected by lowered activity of the periplasmic carbonic anhydrase and decreased photosynthetic affinity for CO2 or dissolved inorganic carbon. The specific growth rate was, however, enhanced significantly by 9.2% only at the limiting low light level. These results indicate that rather than CO2 “fertilization”, the energy saved from down-regulation of CCMs promoted the growth rate of the diatom when light availability is low, in parallel with enhanced respiration under OA to cope with the acidic stress by providing extra energy.
Continue reading ‘Ocean acidification interacts with growth light to suppress CO2 acquisition efficiency and enhance mitochondrial respiration in a coastal diatom’Ocean acidification alters properties of the exoskeleton in adult tanner crabs, Chionoecetes bairdi
Published 13 January 2021 Science ClosedTags: biological response, crustaceans, dissolution, laboratory, morphology, North Atlantic
Ocean acidification can affect the ability of calcifying organisms to build and maintain mineralized tissue. In decapod crustaceans, the exoskeleton is a multilayered structure composed of chitin, protein, and mineral, predominately magnesian calcite or amorphous calcium carbonate (ACC). We investigated the effects of acidification on the exoskeleton of mature (post-terminal-molt) female southern Tanner crabs, Chionoecetes bairdi. Crabs were exposed to one of three pH levels—8.1, 7.8, or 7.5—for two years. Reduced pH led to a suite of body-region-specific effects on the exoskeleton. Microhardness of the claw was 38% lower in crabs at pH 7.5 compared with those at pH 8.1, but carapace microhardness was unaffected by pH. In contrast, reduced pH altered elemental content in the carapace (reduced calcium, increased magnesium), but not the claw. Diminished structural integrity and thinning of the exoskeleton was observed at reduced pH in both body regions; internal erosion of the carapace was present in most crabs at pH 7.5, and the claws of these crabs showed substantial external erosion, with tooth-like denticles nearly or completely worn away. Using infrared spectroscopy, we observed a shift in the phase of calcium carbonate present in the carapace of pH-7.5 crabs: a mix of ACC and calcite was found in the carapace of crabs at pH 8.1, whereas the bulk of calcium carbonate had transformed to calcite in pH-7.5 crabs. With limited capacity for repair, the exoskeleton of long-lived crabs that undergo a terminal molt, such as C. bairdi, may be especially susceptible to ocean acidification.
Continue reading ‘Ocean acidification alters properties of the exoskeleton in adult tanner crabs, Chionoecetes bairdi’Effects of ocean acidification on coral endolithic bacterial communities in Isopora palifera and Porites lobata
Published 12 January 2021 Science ClosedTags: abundance, biological response, BRcommunity, community composition, corals, laboratory, molecular biology, mortality, North Pacific, otherprocess, prokaryotes, protists
Endolithic microbes in coral reefs may act as a nutrient source for their coral hosts. Increasing atmospheric CO2 concentrations are causing ocean acidification (OA), which may affect marine organisms and ecosystems, especially calcifying organisms such as reef-building corals. However, knowledge of how OA affects marine microbes remains limited, and little research has been done on how coral endolithic communities respond to shifting environmental baselines. In this study, the endolithic communities of two common shallow water coral species, Isopora palifera and Porites lobata, were examined to investigate the microbial community dynamics under OA treatments. The colonies were placed in an environment with a partial pressure of carbon dioxide (pCO2) of 1,000 or 400 ppm (control) for 2 months. Several I. palifera colonies bleached and died at 1,000 ppm pCO2, but the P. lobata colonies remained unaffected. Inversely, the endolithic community in P. lobata skeletons showed significant changes after OA treatment, whereas no significant dynamics were observed among the I. palifera endoliths. Our findings suggest that the skeletal structures of different coral species may play a key role in corals host and endoliths under future high-OA scenarios.
Continue reading ‘Effects of ocean acidification on coral endolithic bacterial communities in Isopora palifera and Porites lobata’Gene expression patterns of red sea urchins (Mesocentrotus franciscanus) exposed to different combinations of temperature and pCO2 during early development
Published 11 January 2021 Science ClosedTags: biological response, echinoderms, laboratory, molecular biology, multiple factors, physiology, reproduction, temperature
Background
The red sea urchin Mesocentrotus franciscanus is an ecologically important kelp forest herbivore and an economically valuable wild fishery species. To examine how M. franciscanus responds to its environment on a molecular level, differences in gene expression patterns were observed in embryos raised under combinations of two temperatures (13 °C or 17 °C) and two pCO2 levels (475 μatm or 1050 μatm). These combinations mimic various present-day conditions measured during and between upwelling events in the highly dynamic California Current System with the exception of the 17 °C and 1050 μatm combination, which does not currently occur. However, as ocean warming and acidification continues, warmer temperatures and higher pCO2 conditions are expected to increase in frequency and to occur simultaneously. The transcriptomic responses of the embryos were assessed at two developmental stages (gastrula and prism) in light of previously described plasticity in body size and thermotolerance under these temperature and pCO2 treatments.
Continue reading ‘Gene expression patterns of red sea urchins (Mesocentrotus franciscanus) exposed to different combinations of temperature and pCO2 during early development’Thermal stress reduces pocilloporid coral resilience to ocean acidification by impairing control over calcifying fluid chemistry
Published 11 January 2021 Science ClosedTags: biogeochemistry, biological response, calcification, corals, laboratory, multiple factors, physiology, South Pacific, temperature
The combination of thermal stress and ocean acidification (OA) can more negatively affect coral calcification than an individual stressors, but the mechanism behind this interaction is unknown. We used two independent methods (microelectrode and boron geochemistry) to measure calcifying fluid pH (pHcf) and carbonate chemistry of the corals Pocillopora damicornis and Stylophora pistillata grown under various temperature and pCO2 conditions. Although these approaches demonstrate that they record pHcf over different time scales, they reveal that both species can cope with OA under optimal temperatures (28°C) by elevating pHcf and aragonite saturation state (Ωcf) in support of calcification. At 31°C, neither species elevated these parameters as they did at 28°C and, likewise, could not maintain substantially positive calcification rates under any pH treatment. These results reveal a previously uncharacterized influence of temperature on coral pHcf regulation—the apparent mechanism behind the negative interaction between thermal stress and OA on coral calcification.
Continue reading ‘Thermal stress reduces pocilloporid coral resilience to ocean acidification by impairing control over calcifying fluid chemistry’Acidification stress effect on umbonate veliger larval development in Panopea globosa
Published 11 January 2021 Science ClosedTags: biological response, dissolution, laboratory, molecular biology, mollusks, morphology, North Atlantic, physiology, reproduction, respiration
Highlights
- The pH significantly influenced the biometric variables in Panopea globosa larvae.
- Larvae exposed to lower pH showed shell dissolution at the umbo level.
- The metabolic rate was higher in larvae exposed to acidification compared to the control.
- Nicotinamide adenine dinucleotide dehydrogenase expression levels to pH 7.5 suggest a higher energy requirement.
Abstract
Ocean acidification generates a decrease in calcium carbonate availability essential for biomineralization in organisms such as mollusks. This effect was evaluated on Panopea globosa exposing for 7 days umbonate veliger larvae to two pH treatments: experimental (pH 7.5) and control (pH 8.0). Exposure to pH 7.5 affected growth, reducing larval shell length from 5.15–13.34% compared to the control group. This size reduction was confirmed with electron microscopy, also showing shell damage. The physiological response showed an increase in oxygen consumption in larvae exposed to low pH with a maximum difference of 1.57 nmol O2 h−1 larvae−1 at day 7. The gene expression analyses reported high expression values for nicotinamide adenine dinucleotide (NADH) dehydrogenase and Perlucin in larvae at pH 7.5, suggesting a higher energetic cost in this larval group to maintain homeostasis. In conclusion, this study showed that acidification affected development of P. globosa umbonate veliger larvae.
Ocean acidification increases polyspermy of a broadcast spawning bivalve species by hampering membrane depolarization and cortical granule exocytosis
Published 7 January 2021 Science ClosedTags: biological response, laboratory, mollusks, North Pacific, physiology, reproduction
Highlights
- Ocean acidification (OA) increases polyspermy risk in the blood clam
- Population recruitment of broadcast spawning marine species might be threatened by OA
- OA induces polyspermy via hampering membrane depolarization and cortical reaction
- Disrupted polyspermy blocking may be due to alterations in intracellular Ca2+ and ATP
Abstract
Ensuring that oocytes are fertilized by a single sperm during broadcast spawning is crucial for the fertilization success of many marine invertebrates. Although the adverse impacts of ocean acidification (OA) on various marine species have been revealed in recent years, its impact on polyspermy and the underlying mechanisms involved remain largely unknown. Therefore, in the present study, the effect of OA on polyspermy risk was assessed in a broadcast spawning bivalve, Tegillarca granosa. In addition, the impacts of OA on the two polyspermy blocking processes, the fast block (membrane depolarization) and the permanent block (cortical reaction), were investigated. The results show that the exposure of oocytes to two future OA scenarios (pH 7.8 and pH 7.4) leads to significant increases in polyspermy risk, about 1.70 and 2.38 times higher than the control, respectively. The maximum change in the membrane potential during oocyte membrane depolarization markedly decreased to 15.79% (pH 7.8) and 34.06% (pH 7.4) of the control value. Moreover, the duration of oocyte membrane depolarization was significantly reduced to approximately 63.38% (pH 7.8) and 21.91% (pH 7.4) of the control. In addition, cortical granule exocytosis, as well as microfilament migration, were significantly arrested by OA treatment. Exposure to future OA scenarios also led to significant reductions in the ATP and Ca2+ content of the oocytes, which may explain the hampered polyspermy blocking. Overall, the present study suggests that OA may significantly increase polyspermy risk in T. granosa by inhibiting membrane depolarization and arresting cortical granule exocytosis.
Ocean acidifcation may be increasing the intensity of lightning over the oceans
Published 7 January 2021 Science ClosedTags: chemistry, laboratory
The anthropogenic increase in atmospheric CO2 is not only considered to drive global warming, but also ocean acidification. Previous studies have shown that acidification will affect many aspects of biogenic carbon uptake and release in the surface water of the oceans. In this report we present a potential novel impact of acidification on the flash intensity of lightning discharged into the oceans. Our experimental results show that a decrease in ocean pH corresponding to the predicted increase in atmospheric CO2 according to the IPCC RCP 8.5 worst case emission scenario, may increase the intensity of lightning discharged into seawater by approximately 30 ± 7% by the end of the twenty-first century relative to 2000.
Continue reading ‘Ocean acidifcation may be increasing the intensity of lightning over the oceans’Animal size and sea water temperature, but not pH, influence a repeatable startle response behavior in a wide-ranging marine mollusc
Published 6 January 2021 Science ClosedTags: biological response, chemistry, laboratory, mollusks, morphology, multiple factors, North Atlantic, performance, temperature
Highlights
- We measured startle response (time to open) in mussels following a predator cue.
- We tested effects of temperature, pH and size and measured repeatability.
- Larger mussels opened faster; repeatable startle response; evidence of habituation.
- High temperature increased time to open; no effect of pH.
- Blue mussels are sensitive to temperature and vulnerable to climate change.
Abstracts
Startle response behaviours are important in predator avoidance and escape for a wide array of animals. For many marine invertebrates, however, startle response behaviours are understudied, and the effects of global change stressors on these responses are unknown. We exposed two size classes of blue mussels (Mytilus edulis × trossulus) to different combinations of temperature (15 and 19 °C) and pH (8.2 and 7.5 pHT) for 3 months and subsequently measured individual time to open following a tactile predator cue (i.e. startle response time) over a series of four consecutive trials. Time to open was highly repeatable in the short term and decreased linearly across the four trials. Individuals from the larger size class had a shorter time to open than their smaller-sized counterparts. High temperature increased time to open compared to low temperature, while pH had no effect. These results suggest that bivalve time to open is repeatable, related to relative vulnerability to predation and affected by temperature. Given that increased closure times impact feeding and respiration, the effect of temperature on closure duration may play a role in the sensitivity to ocean warming in this species and contribute to ecosystem level effects.
Continue reading ‘Animal size and sea water temperature, but not pH, influence a repeatable startle response behavior in a wide-ranging marine mollusc’Evaluating bloom potential of the green-tide forming alga Ulva ohnoi under ocean acidification and warming
Published 6 January 2021 Science ClosedTags: algae, biological response, laboratory, mesocosms, morphology, multiple factors, North Pacific, otherprocess, photosynthesis, temperature
Highlights
Mesocosm was conducted to evaluate bloom potential of U. ohnoi in the future ocean.
Bloom potential was higher in ocean acidification with improved C and N metabolism.
Positive metabolic change in ocean acidification were offset by elevated temperature.
The bloom potential decreases when acidification and warming are combined.
Abstract
The occurrence of green-tides, whose bloom potential may be increased by various human activities and biogeochemical process, results in enormous economic losses and ecosystem collapse. In this study, we investigated the ecophysiology of the subtropical green-tide forming alga, Ulva ohnoi complex (hereafter: U. ohnoi), under simulated future ocean conditions in order to predict its bloom potential using photosynthesis and growth measurements, and stable isotope analyses. Our mesocosm system included four experimental conditions that simulated the individual and combined effects of elevated CO2 and temperature, namely control (450 μatm CO2 & 20oC), acidification (900 μatm CO2 & 20oC), warming (450 μatm CO2 & 25oC), and greenhouse (900 μatm CO2 & 25oC). Photosynthetic electron transport rates (rETR) increased significantly under acidification conditions, but net photosynthesis and growth were not affected. In contrast, rETR, net photosynthesis, and growth all decreased significantly under elevated temperature conditions (i.e. both warming and greenhouse). These results represent the imbalance of energy metabolism between electron transport and O2 production that may be expected under ocean acidification conditions. This imbalance appears to be related to carbon and nitrogen assimilation by U. ohnoi. In particular, 13C and 15N discrimination data suggest U. ohnoi prefers CO2 and NH4+ over HCO3– and NO3– as sources of carbon and nitrogen, respectively, and this results in increased N content in the thallus under ocean acidification conditions. Together, our results suggest a trade-off in which the bloom potential of U. ohnoi could increase under ocean acidification due to greater N accumulation and through the saving of energy during carbon and nitrogen metabolism, but that elevated temperatures could decrease U. ohnoi’s bloom potential through a decrease in photosynthesis and growth.
Continue reading ‘Evaluating bloom potential of the green-tide forming alga Ulva ohnoi under ocean acidification and warming’American lobster postlarvae alter gene regulation in response to ocean warming and acidification
Published 5 January 2021 Science ClosedTags: biological response, crustaceans, laboratory, molecular biology, multiple factors, North Atlantic, physiology, temperature
Anthropogenic carbon emissions released into the atmosphere is driving rapid, concurrent increases in temperature and acidity across the world’s oceans. Disentangling the interactive effects of warming and acidification on vulnerable life stages is important to our understanding of responses of marine species to climate change. This study evaluates the interactive effects of these stressors on the acute response of gene expression of postlarval American lobster (Homarus americanus), a species whose geographic range is warming and acidifying faster than most of the world’s oceans. In the context of our experiment, we found two especially noteworthy results: First, although physiological end points have consistently been shown to be more responsive to warming in similar experimental designs, our study found gene regulation to be considerably more responsive to elevated pCO2. Furthermore, the combined effect of both stressors on gene regulation was significantly greater than either stressor alone. Using a full factorial experimental design, lobsters were raised in control and elevated pCO2 concentrations (400 ppm and 1,200 ppm) and temperatures (16°C and 19°C). A transcriptome was assembled from an identified 414,517 unique transcripts. Overall, 1,108 transcripts were differentially expressed across treatments, several of which were related to stress response and shell formation. When temperature alone was elevated (19°C), larvae downregulated genes related to cuticle development; when pCO2 alone was elevated (1,200 ppm), larvae upregulated chitinase as well as genes related to stress response and immune function. The joint effects of end‐century stressors (19°C, 1,200 ppm) resulted in the upregulation of those same genes, as well as cellulase, the downregulation of calcified cuticle proteins, and a greater upregulation of genes related to immune response and function. These results indicate that changes in gene expression in larval lobster provide a mechanism to respond to stressors resulting from a rapidly changing environment.
Continue reading ‘American lobster postlarvae alter gene regulation in response to ocean warming and acidification’Use of a simple empirical model for the accurate conversion of the seawater pH value measured with NIST calibration into seawater pH scales
Published 5 January 2021 Science ClosedTags: chemistry, laboratory, methods
The seawater pH measurement is usually quite complicated because that matrix is characterized by a high ionic strength leading to calibration errors if NIST standards are used. For this matrix, different pH scales like the “total hydrogen ion concentration scale” (TOT) and the “seawater scale” (SWS), are defined, and suitable synthetic seawater solutions must be prepared according to standard procedures to calibrate the glass electrode. This work provides a new approach to make seawater pH measurements by using the glass electrode calibrated with the NIST standards (pHNIST) converting the pHNIST into the right TOT or SWS scales by using empirical equations derived from theoretical thermodynamic data:
pHTOT=pHNIST+0.10383+4.33⋅10−5TS+3.633⋅10−5T2−4.921⋅10−5S2, and pHSWS=pHNIST+0.097733+4.1059⋅10−5TS+3.5437⋅10−5T2−4.941⋅10−5S2,
for the TOT and SWS scales, respectively. These equations are functions of two simple experimental parameters, namely, T = temperature (°C) and S = salinity (PSU, (g/L), Practical Salinity Units). These equations were experimentally validated and the uncertainty of pHTOT and pHSWS was demonstrated to have no statistical difference with the corresponding values obtained following the standard operative procedure (SOP) using commercially unavailable seawater-like buffers. The proposed method has therefore the same performances and it is largely preferable as it avoids long and tedious procedures of the synthetic seawater preparations.
Continue reading ‘Use of a simple empirical model for the accurate conversion of the seawater pH value measured with NIST calibration into seawater pH scales’Effects of experimental ocean acidification on the larval morphology and metabolism of a temperate Sparid, Chrysoblephus laticeps
Published 4 January 2021 Science ClosedTags: biological response, fish, Indian, laboratory, morphology, physiology, reproduction, respiration
Ocean acidification is predicted to have widespread impacts on marine species. The early life stages of fishes, being particularly sensitive to environmental deviations, represent a critical bottleneck to recruitment. We investigated the effects of ocean acidification (∆pH = −0.4) on the oxygen consumption and morphometry during the early ontogeny of a commercially important seabream, Chrysoblephus laticeps, up until flexion. Hatchlings appeared to be tolerant to hypercapnic conditions, exhibiting no difference in oxygen consumption or morphometry between treatments, although the yolk reserves were marginally reduced in the low-pH treatment. The preflexion stages appeared to undergo metabolic depression, exhibiting lower metabolic rates along with lower growth metrics in hypercapnic conditions. However, although the sample sizes were low, the flexion-stage larvae exhibited greater rates of metabolic and growth metric increases in hypercapnic conditions. This study shows that the effects of OA may be stage specific during early ontogeny and potentially related to the development of crucial organs, such as the gills. Future studies investigating the effects of climate change on fish larvae should endeavour to include multiple developmental stages in order to make more accurate predictions on recruitment dynamics for the coming decades.
Continue reading ‘Effects of experimental ocean acidification on the larval morphology and metabolism of a temperate Sparid, Chrysoblephus laticeps’
