Posts Tagged 'laboratory'



High-CO2 levels rather than acidification restrict Emiliania huxleyi growth and performance

The coccolithophore Emiliania huxleyi shows a variety of responses to ocean acidification (OA) and to high-CO2 concentrations, but there is still controversy on differentiating between these two factors when using different strains and culture methods. A heavily calcified type A strain isolated from the Norwegian Sea was selected and batch cultured in order to understand whether acclimation to OA was mediated mainly by CO2 or H+, and how it impacted cell growth performance, calcification, and physiological stress management. Emiliania huxleyi responded differently to each acidification method. CO2-enriched aeration (1200 µatm, pH 7.62) induced a negative effect on the cells when compared to acidification caused by decreasing pH alone (pH 7.60). The growth rates of the coccolithophore were more negatively affected by high pCO2 than by low pH without CO2 enrichment with respect to the control (400 µatm, pH 8.1). High CO2 also affected cell viability and promoted the accumulation of reactive oxygen species (ROS), which was not observed under low pH. This suggests a possible metabolic imbalance induced by high CO2 alone. In contrast, the affinity for carbon uptake was negatively affected by both low pH and high CO2. Photochemistry was only marginally affected by either acidification method when analysed by PAM fluorometry. The POC and PIC cellular quotas and the PIC:POC ratio shifted along the different phases of the cultures; consequently, calcification did not follow the same pattern observed in cell stress and growth performance. Specifically, acidification by HCl addition caused a higher proportion of severely deformed coccoliths, than CO2 enrichment. These results highlight the capacity of CO2 rather than acidification itself to generate metabolic stress, not reducing calcification.

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Ocean acidification alters the acute stress response of a marine fish

The absorption of anthropogenic carbon dioxide in the atmosphere by oceans generates rapid changes in seawater carbonate system and pH, a process termed ocean acidification. Exposure to acidified water can impact the allostatic load of marine organism as the acclimation to suboptimal environments requires physiological adaptive responses that are energetically costly. As a consequence, fish facing ocean acidification may experience alterations of stress response and a compromised ability to cope to additional stress which may impact individuals’ life traits and ultimately their fitness. In this context, we carried out an integrative study investigating the impact of ocean acidification on the physiological and behavioral stress responses to an acute stress in juvenile European sea bass. Fish were long term (11 months) exposed to present day pH/CO 2 condition or acidified water as predicted by IPCC “as business as usual” (RCP8.5) scenario for 2100 and subjected to netting and confinement tests. Fish acclimated to RCP8.5 scenario showed slower post stress return to plasma basal concentrations of cortisol and glucose. We found no clear indication of regulation in the central and interrenal tissues of the expression levels of gluco- and mineralocorticoid receptors and corticoid releasing factor. At 120 minutes post stress, sea bass acclimated to acidified water had divergent neurotransmitters’ concentrations pattern in the hypothalamus (higher serotonin levels and lower GABA and dopamine levels) and a reduction in motor activity. Our experimental data indicate that ocean acidification alters the physiological response to acute stress in European sea bass via the neuroendocrine regulation of the corticotropic axis, a response associated to an alteration of the motor behavioral profile. Overall, this study suggests that behavioral and physiological adaptive response to climate changes related constraints may impact fish resilience to further stressful events.

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Assessing the effects of ocean warming and acidification on the seagrass Thalassia hemprichii

Seagrass beds serve as important carbon sinks, and it is thought that increasing the quantity and quality of such sinks could help to slow the rate of global climate change. Therefore, it will be important to (1) gain a better understanding of seagrass bed metabolism and (2) document how these high-productivity ecosystems are impacted by climate change-associated factors, such as ocean acidification (OA) and ocean warming (OW). A mesocosm-based approach was taken herein in which a tropical, Western Pacific seagrass species Thalassia hemprichii was cultured under either control or OA-simulating conditions; the temperature was gradually increased from 25 to 31 °C for both CO2 enrichment treatments, and it was hypothesized that this species would respond positively to OA and elevated temperature. After 12 weeks of exposure, OA (~1200 ppm) led to (1) increases in underground biomass and root C:N ratios and (2) decreases in root nitrogen content. Rising temperatures (25 to 31 °C) increased the maximum quantum yield of photosystem II (Fv:Fm), productivity, leaf growth rate, decomposition rate, and carbon sequestration, but decreased the rate of shoot density increase and the carbon content of the leaves; this indicates that warming alone does not increase the short-term carbon sink capacity of this seagrass species. Under high CO2 and the highest temperature employed (31 °C), this seagrass demonstrated its highest productivity, Fv:Fm, leaf growth rate, and carbon sequestration. Collectively, then, it appears that high CO2 levels offset the negative effects of high temperature on this seagrass species. Whether this pattern is maintained at temperatures that actually induce marked seagrass stress (likely beginning at 33–34 °C in Southern Taiwan) should be the focus of future research.

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Transgenerational effects and phenotypic plasticity in sperm and larvae of the sea urchin Paracentrotus lividus under ocean acidification

Highlights

  • Transgenerational effects of OA were studied in P. lividus sperm and larvae
  • Gametogenesis under OA resulted in increased sperm ATP content
  • Slower decrease of swimming velocity was found in sperm from males kept at low pH
  • Parental exposure to OA decreased larval survival but increased larval growth
  • Parental pH affected offspring performances more than post-spawning pH

Abstract

In marine organisms, differing degree of sensitivity to ocean acidification (OA) is expected for each life stage, and disturbance at one stage can carry over into the following stage or following generation. In this study we investigated phenotypic changes of sperm and larvae of the sea urchin Paracentrotus lividus in response to different pH conditions (8.0, 7.7, 7.4) experienced by the parents during gametogenesis. In sperm from two-months exposed males, sperm motility, velocity, ATP content, ATP consumption and respiration rate were evaluated at three pH values of the activating medium (8.0, 7.7 and 7.4). Moreover, larvae from each parental group were reared at pH 8.0 and 7.7 for 20 days and larval mortality and growth were then assessed. Sperm motility and respiration rate were not affected either by exposure of males to low pH or by the post-activation pH. Sperm velocity did not differ among post-activation pH values in all sperm groups, but it decreased slower in sperm developed under acidified conditions, suggesting the presence of positive carryover effect on sperm longevity. This positive carryover effect of exposure of males to low pH values was highlighted also for the sperm ATP content, which was higher in these groups of sperm. ATP consumption rate was affected by post-activation pH with higher values at pH 8.0 in sperm from males maintained at control condition and pH 7.7 while the energy consumption appeared to be differently modulated at different experimental conditions. A negative carry over effect of OA was observed on survival of larvae from parents acclimated at pH 7.4 and additive negative effects of both parental and larval exposure to low pH can be suggested. In all groups of larvae, decreased somatic growth was observed at low rearing pH, thus larvae from parents maintained at low pH did not show an increased capability to cope with OA.

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Ocean acidification alleviates dwarf eelgrass (Zostera noltii) lipid landscape remodeling under warming stress

Simple Summary

Expected climate change scenarios will have inevitable and important impacts on key foundation marine species such as seagrasses. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and acidification (ΔpH 0.4) conditions. A severe reduction in the leaf total fatty acid (FA) content was observed in seagrasses individually exposed to hypercapnic or warming conditions, and this depletion was ameliorated under combined exposure to ocean warming and acidification conditions. The tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs). Galactolipid remodeling seems to have key roles in the physiological changes observed in seagrasses under these tested conditions, highlighting the higher impact of warming and that the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Neutral lipids were substantially increased under warming conditions, mainly with increases in C18 FA, impairing their use as substrates to maintain the osmotic balance of the cells. Nonetheless, the pace at which ocean warming is occurring can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid-remodeling capacity.

Abstract

Coastal seagrass meadows provide a variety of essential ecological and economic services, including nursery grounds, sediment stabilization, nutrient cycling, coastal protection, and blue carbon sequestration. However, these ecosystems are highly threatened by ongoing climatic change. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and hypercapnic (ΔpH 0.4) conditions. Warming and hypercapnic conditions were found to induce a severe reduction in the leaf total fatty acid, though the combined treatment substantially alleviated this depletion. The lipid discrimination revealed a significant increase in the relative monogalactosyldiacylglycerol (MGDG) content in both hypercapnic and warming conditions, allied to plastidial membrane stabilization mechanisms. Hypercapnia also promoted enhanced phosphatidylglycerol (PG) leaf contents, a mechanism often associated with thylakoid reinvigoration. In addition to changing the proportion of storage, galacto- and phospholipids, the tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs); however, the combination of both stress conditions alleviated this effect. The observed galactolipid and phospholipid PUFA decreases are compatible with a homeoviscous adaptation, allowing for the maintenance of membrane stability by counteracting excessive membrane fluidity. Neutral lipid contents were substantially increased under warming conditions, especially in C18 fatty acids (C18), impairing their use as substrates for fatty acylated derivatives essential for maintaining the osmotic balance of cells. An analysis of the phospholipid and galactolipid fatty acid profiles as a whole revealed a higher degree of discrimination, highlighting the higher impact of warming and the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Still, it is essential to remember that the pace at which the ocean is warming can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid remodeling capacity.

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Cessation of hardground accretion by the cold-water coralline algae Clathromorphum compactum and Clathromorphum nereostratum predicted within two centuries

Ocean acidification and warming are expected to disproportionately affect high-latitude calcifying species, such as crustose coralline algae. Clathromorphum nereostratum and Clathromorphum compactum are the primary builders of carbonate-hardgrounds in the Aleutians Islands of Alaska and North Atlantic shelf, respectively, providing habitat and settlement substrates for a large number of species. We exposed wild-collected specimens to 12 pCO2/T treatments (344–3322 μatm; 6.38–12.40°C) for 4 months in a factorially crossed, replicated laboratory experiment. Impacts of pCO2/T on algal calcification were quantified from linear extension and buoyant weight. Here we show that, despite belonging to the same genus, Cnereostratum exhibited greater sensitivity to thermal stress, while Ccompactum exhibited greater sensitivity to pH stress. Furthermore, multivariate models of algal calcification derived from the experiment indicate that both Cnereostratum and Ccompactum will commence net dissolution as early as 2120 and 2200 AD, respectively. Our results therefore indicate that near-term climate change may lead to substantial degradation of these species and loss of the critical hardground habitats that they form.

Continue reading ‘Cessation of hardground accretion by the cold-water coralline algae Clathromorphum compactum and Clathromorphum nereostratum predicted within two centuries’

The potential of kelp Saccharina japonica in shielding Pacific oyster Crassostrea gigas from elevated seawater pCO2 stress

Ocean acidification (OA) caused by elevated atmospheric CO2 concentration is predicted to have negative impacts on marine bivalves in aquaculture. However, to date, most of our knowledge is derived from short-term laboratory-based experiments, which are difficult to scale to real-world production. Therefore, field experiments, such as this study, are critical for improving ecological relevance. Due to the ability of seaweed to absorb dissolved carbon dioxide from the surrounding seawater through photosynthesis, seaweed has gained theoretical attention as a potential partner of bivalves in integrated aquaculture to help mitigate the adverse effects of OA. Consequently, this study investigates the impact of elevated pCO2 on the physiological responses of the Pacific oyster Crassostrea gigas in the presence and absence of kelp (Saccharina japonica) using in situ mesocosms. For 30 days, mesocosms were exposed to six treatments, consisting of two pCO2 treatments (500 and 900 μatm) combined with three biotic treatments (oyster alone, kelp alone, and integrated kelp and oyster aquaculture). Results showed that the clearance rate (CR) and scope for growth (SfG) of C. gigas were significantly reduced by elevated pCO2, whereas respiration rates (MO2) and ammonium excretion rates (ER) were significantly increased. However, food absorption efficiency (AE) was not significantly affected by elevated pCO2. The presence of S. japonica changed the daytime pHNBS of experimental units by ~0.16 units in the elevated pCO2 treatment. As a consequence, CR and SfG significantly increased and MO2 and ER decreased compared to C. gigas exposed to elevated pCO2 without S. japonica. These findings indicate that the presence of S. japonica in integrated aquaculture may help shield C. gigas from the negative effects of elevated seawater pCO2.

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Multiscale mechanical consequences of ocean acidification for cold-water corals

Ocean acidification is a threat to deep-sea corals and could lead to dramatic and rapid loss of the reef framework habitat they build. Weakening of structurally critical parts of the coral reef framework can lead to physical habitat collapse on an ecosystem scale, reducing the potential for biodiversity support. The mechanism underpinning crumbling and collapse of corals can be described via a combination of laboratory-scale experiments and mathematical and computational models. We synthesise data from electron back-scatter diffraction, micro-computed tomography, and micromechanical experiments, supplemented by molecular dynamics and continuum micromechanics simulations to predict failure of coral structures under increasing porosity and dissolution. Results reveal remarkable mechanical properties of the building material of cold-water coral skeletons of 462 MPa compressive strength and 45–67 GPa stiffness. This is 10 times stronger than concrete, twice as strong as ultrahigh performance fibre reinforced concrete, or nacre. Contrary to what would be expected, CWCs retain the strength of their skeletal building material despite a loss of its stiffness even when synthesised under future oceanic conditions. As this is on the material length-scale, it is independent of increasing porosity from exposure to corrosive water or bioerosion. Our models then illustrate how small increases in porosity lead to significantly increased risk of crumbling coral habitat. This new understanding, combined with projections of how seawater chemistry will change over the coming decades, will help support future conservation and management efforts of these vulnerable marine ecosystems by identifying which ecosystems are at risk and when they will be at risk, allowing assessment of the impact upon associated biodiversity.

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Natural analogues in pH variability and predictability across the coastal Pacific estuaries: extrapolation of the increased oyster dissolution under increased pH amplitude and low predictability related to ocean acidification

Coastal-estuarine habitats are rapidly changing due to global climate change, with impacts influenced by the variability of carbonate chemistry conditions. However, our understanding of the responses of ecologically and economically important calcifiers to pH variability and temporal variation is limited, particularly with respect to shell-building processes. We investigated the mechanisms driving biomineralogical and physiological responses in juveniles of introduced (Pacific; Crassostrea gigas) and native (Olympia; Ostrea lurida) oysters under flow-through experimental conditions over a six-week period that simulate current and future conditions: static control and low pH (8.0 and 7.7); low pH with fluctuating (24-h) amplitude (7.7 ± 0.2 and 7.7 ± 0.5); and high-frequency (12-h) fluctuating (8.0 ± 0.2) treatment. The oysters showed physiological tolerance in vital processes, including calcification, respiration, clearance, and survival. However, shell dissolution significantly increased with larger amplitudes of pH variability compared to static pH conditions, attributable to the longer cumulative exposure to lower pH conditions, with the dissolution threshold of pH 7.7 with 0.2 amplitude. Moreover, the high-frequency treatment triggered significantly greater dissolution, likely because of the oyster’s inability to respond to the unpredictable frequency of variations. The experimental findings were extrapolated to provide context for conditions existing in several Pacific coastal estuaries, with time series analyses demonstrating unique signatures of pH predictability and variability in these habitats, indicating potentially benefiting effects on fitness in these habitats. These implications are crucial for evaluating the suitability of coastal habitats for aquaculture, adaptation, and carbon dioxide removal strategies.

Continue reading ‘Natural analogues in pH variability and predictability across the coastal Pacific estuaries: extrapolation of the increased oyster dissolution under increased pH amplitude and low predictability related to ocean acidification’

Transcriptomic responses of adult versus juvenile Atlantids to ocean acidification

Shelled holoplanktonic gastropods are among the most vulnerable calcifiers to ocean acidification. They inhabit the pelagic environment and build thin and transparent shells of aragonite, a metastable form of calcium carbonate. While shelled pteropods have received considerable attention and are widely regarded as bioindicators of ocean acidification, atlantids have been much less studied. In the open ocean, atlantids are uniquely positioned to address the effects of ocean acidification at distinct trophic levels. From juvenile to adult, they undergo dramatic metamorphosis. As adults they are predatory, feeding primarily on shelled pteropods, copepods and other zooplankton, while as juveniles they feed on algae. Here we investigated the transcriptome and the impact of a three-day CO2 exposure on the gene expression of adults of the atlantid Atlanta ariejansseni and compared these to results previously obtained from juveniles. Individuals were sampled in the Southern Subtropical Convergence Zone (Atlantic Ocean) and exposed to ocean chemistry simulating past (~mid-1960s), present (ambient) and future (2050) conditions. In adults we found that the changes in seawater chemistry had significantly affected the expression of genes involved in biomineralization and the immune response, although there were no significant differences in shell growth between the three conditions. In contrast, juveniles experienced substantial changes in shell growth and a broader transcriptomic response. In adults, 1170 genes had the same direction of expression in the past and future treatments when compared to the ambient. Overall, this type of response was more common in adults (8.6% of all the genes) than in juveniles (3.9%), whereas a linear response with decreasing pH was more common in juveniles (7.7%) than in adults (4.5%). Taken together, these results suggest that juveniles are more sensitive to increased acidification than adults. However, experimental limitations including short incubation times, one carboy used for each treatment and two replicates for transcriptome analysis, require us to be cautious about these conclusions. We show that distinct transcriptome profiles characterize the two life stages, with less than 50% of shared transcripts. This study provides an initial framework to understand how ocean acidification may affect the molecular and calcification responses of adult and juvenile atlantids.

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A triple threat: ocean warming, acidification and rare earth elements exposure triggers a superior antioxidant response and pigment production in the adaptable Ulva rigida

Highlights

  • La and Gd were accumulated in 24h;
  • Elimination of La and Gd did not occur in U. rigida;
  • La and Gd showed different accumulation and elimination patterns in future predicted scenarios;
  • La and Gd triggered an efficient antioxidant defence response in U. rigida;
  • REE and climate change exposure requested a superior antioxidant response.

Abstract

Anthropogenic increased atmospheric CO2 concentrations will lead to a drop of 0.4 units of seawater pH and ocean warming up to 4.8°C by 2100. Contaminant’s toxicity is known to increase under a climate change scenario. Rare earth elements (REE) are emerging contaminants, that until now have no regulation regarding maximum concentration and discharge into the environment and have become vital to new technologies such as electric and hybrid-electric vehicle batteries, wind turbine generators and low-energy lighting. Studies of REE, namely Lanthanum (La) and Gadolinium (Gd), bioaccumulation, elimination, and toxicity in a multi-stressor environment (e.g., warming and acidification) are lacking. Hence, we investigated the algae phytoremediation capacity, the ecotoxicological responses and total chlorophyll and carotenoid contents in Ulva rigida during 7 days of co-exposure to La or Gd (15 µg L−1 or 10 µg L−1, respectively), and warming and acidification. Additionally, we assessed these metals elimination, after a 7-day phase. After one day of experiment La and Gd clearly showed accumulation/adsorption in different patterns, at future conditions. Unlikely for Gd, Warming and Acidification contributed to the lowest La accumulation, and increased elimination. Lanthanum and Gd triggered an adequate activation of the antioxidant defence system, by avoiding lipid damage. Nevertheless, REE exposure in a near-future scenario triggered an overproduction of ROS that requested an enhanced antioxidant response. Additionally, an increase in total chlorophyll and carotenoids could also indicate an unforeseen energy expense, as a response to a multi-stressor environment.

Continue reading ‘A triple threat: ocean warming, acidification and rare earth elements exposure triggers a superior antioxidant response and pigment production in the adaptable Ulva rigida’

Understanding the impacts of environment and parasitism on Eastern oyster (Crassostrea virginica) vulnerability to ocean acidification

The global process of ocean acidification caused by the absorption of increased atmospheric carbon dioxide decreases the concentration of carbonate ions and reduces the associated seawater saturation state (ΩCaCO3) – making it more energetically costly for marine calcifying organisms to build their shells or skeletons. Bivalves are particularly vulnerable to the adverse effects of ocean acidification on calcification, and they inhabit estuaries and coastal zones – regions most susceptible to ocean acidification. However, the response of an individual to elevated pCO2 can depend on the carbonate chemistry dynamics of its current environment and the environment of its parents. Additionally, an organism’s response to ocean acidification can depend on its ability to control the chemistry at the site of calcification. Biotic and abiotic stressors can modify bivalves’ control of calcifying fluid chemistry – known as extrapallial fluid (EPF). Understanding the responses of bivalves – which are foundation species – to ocean acidification is essential for predicting the impacts of oceanic change on marine communities. This dissertation uses a culturally, ecologically, and economically important bivalve in the northwest Atlantic – the Eastern oyster (Crassostrea virginica) – to explore the effects of environment and species interactions on responses to elevated pCO2.

Chapter 2 describes a field study that characterized diurnal and seasonal carbonate chemistry dynamics of two estuaries in the Gulf of Maine that support Eastern oyster populations. The estuaries were monitored at high temporal resolution (half-hourly) over four years (2018-2021) using pH and conductivity loggers. Measured pH, salinity, and temperature were used to calculate carbonate chemistry parameters. Both estuaries exhibited strong seasonal and diurnal fluctuations in carbonate chemistry. They also experienced pCO2 values that greatly exceeded current atmospheric carbon dioxide levels and those projected for the year 2100.

Chapter 3 describes a laboratory experiment that examined the capacity of intergenerational exposure to mitigate the adverse effects of ocean acidification on larval growth, shell morphology, and survival. Adult oysters were cultured in control or elevated pCO2 conditions for 30 days then crossed using a North Carolina II cross design. Larvae were grown for three days under control and elevated pCO2 conditions. Intergenerational exposure to elevated pCO2 conditions benefited early larval growth and shell morphology, but not survival. However, parental exposure was insufficient to completely counteract the adverse effects of the elevated pCO2 treatment on shell formation and survival.

Chapter 4 describes a laboratory experiment that examined the interplay between ocean acidification and parasite-host dynamics. Eastern oysters infested and not infested with bioeroding sponge (Cliona sp.) were cultured under three pCO2 conditions (539, 1040, 3294 ppm) and two temperatures (23, 27˚C) for 70 days to assess oyster control of EPF chemistry, growth, and survival. Bioeroding sponge infestation and elevated pCO2 reduced oyster net calcification and EPF pH but did not affect condition or survival. Infested oyster EPF pH was consistently lower than seawater pH, while EPF dissolved inorganic carbon was consistently elevated relative to seawater. These findings suggested that infested oysters effectively precipitated repair shell to prevent seawater intrusion into extrapallial fluid through bore holes across all treatments.

Chapter 5 characterizes the concentration of a suite of 56 elements normalized to calcium in EPF and shell of Crassostrea virginica grown under three pCO2 conditions (570, 990, 2912 ppm) and sampled at four timepoints (days 2, 9, 79, 101) to assess effects of pCO2 on organismal control of EPF and shell elemental composition and EPF-to-shell elemental partitioning. Elevated pCO2 significantly influenced the relative abundance of elements in the EPF (29) and shell (13) and altered EPF-to-shell elemental partitioning for 45 elements. Importantly, elevated pCO2 significantly influenced the concentration of several elements in C. virginica shell that are used in other biogenic carbonates as paleo-proxies for other environmental parameters. This result suggests that elevated pCO2 could influence the accuracy of paleo reconstructions.

Overall, this dissertation provides insights that can help improve our understanding of past, present, and future ocean environments. Understanding current local carbonate chemistry dynamics and the capacity for C. virginica to acclimate intergenerationally to elevated pCO2 can inform site and stock selection for aquaculture and restoration efforts. Studying parasite-host environment interactions provides critical insights into the potential for parasitism to alter responses to future ocean acidification. Finally, exploring the impact of elevated pCO2 on elemental composition of EPF and shell allowed us to understand better biomineralization processes, identify potential proxies for seawater pCO2 in bivalves, and offer insights that could help improve the accuracy of paleo reconstructions.

Continue reading ‘Understanding the impacts of environment and parasitism on Eastern oyster (Crassostrea virginica) vulnerability to ocean acidification’

Ocean acidification impacts fish larvae but warming could compensate juveniles

Related content

A related article has been published: Effects of ocean acidification over successive generations decrease resilience of larval European sea bass to ocean acidification and warming but juveniles could benefit from higher temperatures in the NE Atlantic

A 40 day old European sea bass (Dicentrarchus labrax) larva: Photo credit: Sarah Howald.

As we pump more CO2 into the atmosphere, the pH of the oceans is decreasing and although a reduction of 0.1 pH units may not sound much, the reality is that the acidity of the seas has increased by 30% since the start of the Industrial Revolution in the 18th century. But no one knew how much of an impact decreasing pH might have on long-lived fish species. ‘Fish had been thought to be less vulnerable to ocean acidification due to well-developed acid–base regulation systems’, says Sarah Howald from the Alfred Wegener Institute for Polar and Marine Research (AWI), Germany. However, scientists have recently discovered that fish larvae may be more vulnerable than thought. Some grew faster in more acidic waters, while others suffered tissue and hearing damage in addition to growing more slowly. Yet, no one knew how ocean acidification might impact subsequent generations. Felix Mark from AWI, with colleagues from Germany and France, embarked on an ambitious 5.5 year investigation to find out how European sea bass (Dicentrarchus labrax) larvae and their eventual offspring deal with acidic conditions.

In October 2013, at the Ifremer-Centre de Bretagne, France, Guy Claireaux (University of Brest, France), José Zambonino and David Mazurais (both from Ifremer), Myron Peck (University of Hamburg, Germany) and Mark allocated recently hatched sea bass larvae to small tanks of seawater pumped in from the Bay of Brest at summer temperatures (19°C) while other larvae lived in tanks of seawater where the acidity had been raised to 1700 μatm CO2, the IPCC’s prediction for seawater CO2 concentrations 120 years in the future. Once the larvae had developed into juveniles (∼2.5 months old), the team relocated the youngsters to larger cool (15°C) tanks, maintaining the two different pH levels until the fish were adult (spring 2017), when the researchers selected ∼30 adult fish each from the two water conditions to rehome in palatial 3000 l tanks. Then, in March 2018, the 5 year old adults spawned to produce the next generation of larvae. But this time the scientists added a twist, dividing the offspring of the parents from the modern day (current CO2) seawater conditions and those of the parents raised in the acidic future water conditions (1700 μatm CO2) into cool and warm tanks, to simulate climate change. Meanwhile, the team kept track of the first and the second generations as they grew and developed.

Initially, the first generation of sea bass youngsters didn’t seem to be affected by their acidic start in life and neither did their offspring. However, when the team altered the water temperature as the second generation developed in the acidic future water, they found the larvae from the warmer (20°C) tank were much smaller when they metamorphosed into juveniles than those in cool acidic seawater and those that developed in modern warm water. Mark suspects that the warmer high-CO2 conditions in the future could impair energy production by the youngsters’ mitochondria, limiting their growth. However, once the larvae developed into juvenile fish, they seemed to benefit, growing faster, although the team isn’t sure whether the warmth was accelerating the fish’s growth or whether the acidity failed to impair the growing juveniles.

The team warns that the faster growth of larvae in a warmer more acidic world could place them at risk if there is insufficient food for the rapidly growing youngsters. But it seems that if the youngsters develop successfully into juvenile fish, their chances may improve.

Continue reading ‘Ocean acidification impacts fish larvae but warming could compensate juveniles’

Effects of seawater pCO2 on the skeletal morphology of massive Porites spp. corals

Ocean acidification alters the dissolved inorganic carbon chemistry of seawater and can reduce the calcification rates of tropical corals. Here we explore the effect of altering seawater pCO2 on the skeletal morphology of 4 genotypes of massive Porites spp. which display widely different calcification rates. Increasing seawater pCO2 causes significant changes in in the skeletal morphology of all Porites spp. studied regardless of whether or not calcification was significantly affected by seawater pCO2. Both the median calyx size and the proportion of skeletal surface occupied by the calices decreased significantly at 750 µatm compared to 400 µatm indicating that polyp size shrinks in this genus in response to ocean acidification. The coenosteum, connecting calices, expands to occupy a larger proportion of the coral surface to compensate for this decrease in calyx area. At high seawater pCO2 the spines deposited at the skeletal surface became more numerous and the trabeculae (vertical skeletal pillars) became significantly thinner in 2 of the 4 genotypes. The effect of high seawater pCO2 is most pronounced in the fastest growing coral and the regular placement of trabeculae and synapticulae is disturbed in this genotype resulting in a skeleton that is more randomly organised. The study demonstrates that ocean acidification decreases the polyp size and fundamentally alters the architecture of the skeleton in this major reef building species from the Indo-Pacific Ocean.

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Single and combined ecotoxicological effects of ocean warming, acidification and lanthanum exposure on the surf clam (Spisula solida)

Highlights

  • Lanthanum was bioaccumulated after just one day of exposure.
  • Elimination did not occur during the 7-day depuration phase.
  • The biochemical response was triggered, however damage occurred.
  • The La toxic effects are more severe in a changing world.

Abstract

Lanthanum (La) is one of the most abundant emergent rare earth elements. Its release into the environment is enhanced by its use in various industrial applications. In the aquatic environment, emerging contaminants are one of the stressors with the ability to compromise the fitness of its inhabitants. Warming and acidification can also affect their resilience and are another consequence of the growing human footprint on the planet. However, from information gathered in the literature, a study on the effects of ocean warming, acidification, and their interaction with La was never carried out. To diminish this gap of knowledge, we explored the effects, combined and as single stressors, of ocean warming, acidification, and La (15 μg L−1) accumulation and elimination on the surf clam (Spisula solida). Specimens were exposed for 7 days and depurated for an additional 7-day period. Furthermore, a robust set of membrane-associated, protein, and antioxidant enzymes and non-enzymatic biomarkers (LPO, HSP, Ub, SOD, CAT, GPx, GST, TAC) were quantified. Lanthanum was bioaccumulated after just one day of exposure, in both control and climate change scenarios. A 7-day depuration phase was insufficient to achieve control values and in a warming scenario, La elimination was more efficient. Biochemical response was triggered, as highlighted by enhanced SOD, CAT, GST, and TAC levels, however as lipoperoxidation was observed it was insufficient to detoxify La and avoid damage. The HSP was largely inhibited in La treatments combined with warming and acidification. Concomitantly, lipoperoxidation was highest in clams exposed to La, warming, and acidification combined. The results highlight the toxic effects of La on this bivalve species and its enhanced potential in a changing world.

Continue reading ‘Single and combined ecotoxicological effects of ocean warming, acidification and lanthanum exposure on the surf clam (Spisula solida)’

Effect of different pCO2 concentrations in seawater on meiofauna: abundance of communities in sediment and survival rate of harpacticoid copepods

The amount of CO2 dissolved in the ocean has been increasing continuously, and the results using climate change models show that the CO2 concentration of the ocean will increase by over 1000 ppm by 2100. Ocean acidification is expected to have a considerable impact on marine ecosystems. To find out about the impacts of ocean acidification on meiofaunal communities and copepod groups, we analyzed the differences in the abundance of meiofauna communities in sediment and the survival rate of harpacticoid copepod assemblages separated from the sediment, between 400 and 1000 ppm pCO2 for a short period of 5 days. In experiments with communities in sediments exposed to different pCO2 concentrations, there was no significant difference in the abundance of total meiofauna and nematodes. However, the abundance of the harpacticoid copepod community was significantly lower at 1000 ppm than that at 400 ppm pCO2. On the other hand, in experiments with assemblages of harpacticoid copepods directly exposed to seawater, there was no significant difference in their survival rates between the two concentrations. Our findings suggest that a CO2 concentration of 1000 ppm in seawater can cause changes in the abundance of specific taxa such as harpacticoid copepods among the meiofauna communities in sediments.

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Adaptive potential of coastal invertebrates to environmental stressors and climate change

Climate change presents multiple stressors that are impacting marine life. As carbon dioxide emissions continue to increase in the atmosphere, atmospheric and sea water temperatures increase. In addition, more carbon dioxide is absorbed into the oceans, reducing pH and aragonite saturation state, resulting in ocean acidification (OA). Tightly coupled with OA is hypoxia due to deep stratified sea water becoming increasingly acidified and deoxygenated. The effects of these climate stressors have been studied in detail for only a few marine animal models. However, there are still many taxa and developmental stages in which we know very little about the impacts. Using genomic techniques, we examine the adaptive potential of three local marine invertebrates under three different climate stressors: marine disease exacerbated by thermal stress, OA, and combined stressors OA with hypoxia (OAH). As sea water temperatures rise, the prevalence of marine diseases increases, as seen in the sea star wasting syndrome (SSWS). The causation of SSWS is still widely debated; however reduced susceptibility to SSWS could aid in understanding disease progression. By examining genetic variation in Pisaster ochraceous collected during the SSWS outbreak, we observed weak separation between symptomatic and asymptomatic individuals. OA has been widely studied in many marine organisms, including Crassostrea gigas. However, limited studies have parsed the effects of OA during settlement, with no studies assessing the functionality of settlement and how it is impacted by OA. We investigated the effects of OA on settlement and gene expression during the transition from larval to juvenile stages in Pacific oysters. While OA and hypoxia are common climate stressors examined, the combined effects have scarcely examined. Further, the impacts of OAH have been narrowly focused on a select few species, with many economically important organisms having no baseline information on how they will persist as OAH severity increases. To address these gaps in our knowledge, we measured genetic variation in metabolic rates during OA for the species Haliotis rufescens to assess their adaptive potential through heritability measurements. We discuss caveats and considerations when utilizing similar heritability estimate methods for other understudied organisms. Together, these studies will provide novel information on the biological responses and susceptibility of difference coastal species to stressors associated with global climate change. These experiments provide information on both the vulnerability of current populations and their genetic potential for adaptation to changing ocean conditions.

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CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time

Carbonate-poor sandy sediments comprise much of the shelf area, and—despite their low CaCO3 content—contain a significant pool of CaCO3 base available to neutralize ocean acid. Here, we conducted flow-through column experiments on permeable, carbonate-poor sand obtained from Catalina Island, CA, to quantify CaCO3 dissolution across a range of current and future seawater conditions. Using 13C isotope mass balance, we show that dissolution depends both on the CaCO3 saturation state (Ω) of the inflowing seawater, as well as porewater residence time. At current ocean conditions (Ωaragonite =2.4 and Ωcalcite =3.7 at our field site), dissolution was negligible for porewater residence times <1.8 h, but increased thereafter, following sufficient production of CO2 from aerobic respiration. As Ω of inlet water was lowered, simulating future ocean conditions, dissolution began earlier and rates increased. The response to acidification was similar to previously reported observations in carbonate-rich shelf environments, suggesting that carbonate-poor sediments have the potential to support enhanced dissolution in an acidifying ocean, given sufficient CaCO3 substrate. With continued acidification projected to occur this century, these sediments could transition from a net source of acid to the overlying seawater (production of alkalinity to dissolved inorganic carbon, ΔAlk/ΔDIC<1) to net source of buffering capacity (ΔAlk/ΔDIC>1) when overlying seawater Ωaragonite reaches 0.96 to 0.69 (Ωcalcite = 1.50 and 1.07), depending on porewater residence time. In some areas with naturally acidic water, this threshold has already been reached.

Continue reading ‘CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time’

Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming

Coastal habitats are experiencing decreases in seawater pH and increases in temperature due to anthropogenic climate change. The Caribbean king crab, Maguimithrax spinosissimus, plays a vital role on Western Atlantic reefs by grazing macroalgae that competes for space with coral recruits. Therefore, identifying its tolerance to anthropogenic stressors is critically needed if this species is to be considered as a potential restoration management strategy in coral reef environments. We examined the effects of temperature (control: 28 °C and elevated: 31 °C) and pH (control: 8.0 and reduced pH: 7.7) on the king crab’s larval and early juvenile survival, molt-stage duration, and morphology in a fully crossed laboratory experiment. Survival to the megalopal stage was reduced (13.5% lower) in the combined reduced pH and elevated temperature treatment relative to the control. First-stage (J1) juveniles delayed molting by 1.5 days in the reduced pH treatment, while second-stage (J2) crabs molted 3 days earlier when exposed to elevated temperature. Juvenile morphology did not differ among treatments. These results suggests that juvenile king crabs are tolerant to changes associated with climate change. Given the important role of the king crab as a grazer of macroalgae, its tolerance to climate stressors suggests that it could benefit restoration efforts aimed at making coral reefs more resilient to increasingly warm and acidic oceans into the future.

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The effects of ocean acidification on microbial nutrient cycling and productivity in coastal marine sediments

Ocean Acidification (OA), commonly referred to as the “other CO₂ problem,” illustrates the current rise in atmospheric carbon dioxide (CO₂) levels, precipitated in large by human-related activity (e.g., fossil fuel combustion and mass deforestation). The dissolution of atmospheric CO₂ into the surface of the ocean over time has reduced oceanic pH levels by 0.1 units since the start of the pre-industrial era and has resulted in wholesale shifts in seawater carbonate chemistry on a planetary scale. The chemical processes of ocean acidification are increasingly well documented, demonstrating clear rates of increase for global CO₂ emissions predicted by the IPCC (Intergovernmental Panel on Climate Change) under the business-as-usual CO₂ emissions scenario. The ecological impact of ocean acidification alters seawater chemical speciation and disrupts vital biogeochemical cycling processes for various chemicals and compounds. Whereby the unidentified potential fallout of this is the cascading effects on the microbial communities within the benthic sediments. These microorganisms drive the marine ecosystem through a network of vast biogeochemical cycling processes aiding in the moderation of ecosystem-wide primary productivity and fundamentally regulating the global climate. The benthic sediments are determinably one of the largest and most diverse ecosystems on the planet. Marine sediments are also conceivably one of the most productive in terms of microbial activity and nutrient flux between the water-sediment interface (i.e., boundary layer). The absorption and sequestering of CO₂ from the atmosphere have demonstrated significant impacts on various marine taxa and their associated ecological processes. This is commonly observed in the reduction in calcium carbonate saturation states in most shell-forming organisms (i.e., plankton, benthic mollusks, echinoderms, and Scleractinia corals). However, the response of benthic sediment microbial communities to a reduction in global ocean pH remains considerably less well characterized. As these microorganisms operate as the lifeblood of the marine ecosystem, understanding their response and physiological plasticity to increased levels of CO₂ is of critical importance when it comes to investigating regional and global implications for the effects of ocean acidification.

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