Posts Tagged 'respiration'

Ocean acidification increases inorganic carbon over organic carbon in shrimp’s exoskeleton

Published 23 May 2023 Science Leave a Comment
Tags: , , , , , ,

Highlights

  • PIC: POC ratio in shrimps’ exoskeleton may increase under future OA.
  • Hyper-calcification and increased respiration are possible in shrimps under OA releasing more CO2 into the water.
  • Increased PIC: POC ratio may impact the ecosystem functions as well as the carbon cycle.

Abstract

Ocean acidification (OA) may either increase or have a neutral effect on the calcification in shrimp’s exoskeleton. However, investigations on changes in the carbon composition of shrimp’s exoskeletons under OA are lacking. We exposed juvenile Pacific white shrimps to target pHs of 8.0, 7.9, and 7.6 for 100 days to evaluate changes in carapace thickness, total carbon (TC), particulate organic carbon (POC), particulate inorganic carbon (PIC), calcium, and magnesium concentrations in their exoskeletons. The PIC: POC ratio of shrimp in pH 7.6 treatment was significantly higher by 175 % as compared to pH 8.0 treatment. Thickness and Ca% in pH 7.6 treatment were significantly higher as compared to pH 8.0 treatment (90 % and 65 %, respectively). This is the first direct evidence of an increased PIC: POC ratio in shrimp exoskeletons under OA. In the future, such changes in carbon composition may affect the shrimp population, ecosystem functions, and regional carbon cycle.

Continue reading ‘Ocean acidification increases inorganic carbon over organic carbon in shrimp’s exoskeleton’

Ocean acidification enhances primary productivity and nocturnal carbonate dissolution in intertidal rock pools

Published 18 May 2023 Science Leave a Comment
Tags: , , , , , , , , ,

Human CO2 emissions are modifying ocean carbonate chemistry, causing ocean acidification, and likely already impacting marine ecosystems. In particular, there is concern that coastal, benthic calcifying organisms will be negatively affected by ocean acidification, a hypothesis largely supported by laboratory studies. The inter-relationships between carbonate chemistry and marine calcifying communities in situ are complex and natural mesocosms such as tidal pools can provide useful community-level insights. In this study, we manipulated the carbonate chemistry of intertidal pools to investigate the influence of future ocean acidification on net community production (NCP) and calcification (NCC) at emersion. Adding CO2 at the start of the tidal emersion to simulate future acidification (+1500 μatm pCO2, target pH: 7.5) modified net production and calcification rates in the pools. By day, pools were fertilized by the increased CO2 (+20 % increase in NCP, from 10 to 12 mmol O2 m−2 hr−1), while there was no measurable impact on NCC. During the night, pools experienced net community dissolution (NCC < 0), even in present-day conditions, when waters were supersaturated with regards to aragonite. Adding CO2 in the pools increased nocturnal dissolution rates by 40 % (from −0.7 to −1.0 mmol CaCO3 m−2 hr−1) with no consistent impact on night community respiration. Our results suggest that ocean acidification is likely to alter temperate intertidal community metabolism on sub-daily timescales, enhancing both diurnal community production and nocturnal calcium carbonate dissolution.

Continue reading ‘Ocean acidification enhances primary productivity and nocturnal carbonate dissolution in intertidal rock pools’

Sponge organic matter recycling: reduced detritus production under extreme environmental conditions

Published 14 April 2023 Science Closed
Tags: , , , , , , , , , , , , , , , , ,

Highlights

  • Sponge metabolism was measured at the natural laboratory of Bouraké where sponges are naturally exposed to extreme conditions associated with tidal phase.
  • The photosymbiotic HMA sponge Rhabdastrella globostellata was able to cope with extreme acidification and deoxygenation seawater.
  • Photosynthetic activity of sponge symbionts was negatively affected during extreme environmental conditions.
  • The sponge loop pathway was disrupted during low tide, which correlated with extreme acidification, deoxygenation and warming seawater.

Abstract

Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions. During two years (2018 and 2020), we measured the organic carbon, nutrient recycling, and photosynthetic activity of the massive HMA, photosymbiotic sponge Rhabdastrella globostellata at the natural laboratory of Bouraké in New Caledonia, where the physical and chemical composition of seawater regularly change according to the tide. We found that while sponges experienced acidification and low dissolved oxygen at low tide in both sampling years, a change in organic carbon recycling whereby sponges stopped producing detritus (i.e., the sponge loop) was only found when sponges also experienced higher temperature in 2020. Our findings provide new insights into how important trophic pathways may be affected by changing ocean conditions.

Continue reading ‘Sponge organic matter recycling: reduced detritus production under extreme environmental conditions’

Embryonic encapsulated development of the gastropod Acanthina monodon is impacted by future environmental changes of temperature and pCO2

Published 13 April 2023 Science Closed
Tags: , , , , , , , , , , , ,

Egg capsules of the gastropod Acanthina monodon were maintained during the entire period of encapsulated development at three temperatures (10, 15, 20 °C) and two pCO2 levels (400, 1200 μatm). Embryos per capsule, size at hatching, time to hatching, embryonic metabolic rates, and the resistance of juveniles to shell breakage were quantified. No embryos maintained at 20 °C developed to hatching. The combination of temperature and pCO2 levels had synergistic effects on hatching time and developmental success, antagonistic effects on number of hatchlings per capsule, resistance to juvenile shell cracking and metabolism, and additive effect on hatching size. Juveniles hatched significantly sooner at 15 °C, independent of the pCO2 level that they had been exposed to, while individuals hatched at significantly smaller sizes if they had been held under 15 °C/1200 μatm rather than at 10 °C/low pCO2. Embryos held at the higher pCO2 had a significantly greater percentage of abnormalities. For capsules maintained at low pCO2 and 15 °C, emerging juveniles had less resistance to shell breakage. Embryonic metabolism was significantly higher at 15 °C than at 10 °C, independent of pCO2 level. The lower metabolism occurred in embryos maintained at the higher pCO2 level. Thus, in this study, temperature was the factor that had the greatest effect on the encapsulated development of A. monodon, increasing the metabolism of the embryos and consequently accelerating development, which was expressed in a shorter intracapsular development time, but with smaller individuals at hatching and a lower resistance of their shells to breakage. On the other hand, the high pCO2 level suppressed metabolism, prolonged intracapsular development, and promoted more incomplete development of the embryos. However, the combination of the two factors can mitigate–to some extent–the adverse effects of both incomplete development and lower resistance to shell breakage.

Continue reading ‘Embryonic encapsulated development of the gastropod Acanthina monodon is impacted by future environmental changes of temperature and pCO2’

Deoxygenation enhances photosynthetic performance and increases N2 fixation in the marine cyanobacterium Trichodesmium under elevated pCO2

Published 12 April 2023 Science Closed
Tags: , , , , , , , , ,

Effects of changed levels of dissolved O2 and CO2 on marine primary producers are of general concern with respect to ecological effects of ongoing ocean deoxygenation and acidification as well as upwelled seawaters. We investigated the response of the diazotroph Trichodesmium erythraeum IMS 101 after it had acclimated to lowered pO2 (~60 μM O2) and/or elevated pCO2 levels (HC, ~32 μM CO2) for about 20 generations. Our results showed that reduced O2 levels decreased dark respiration significantly, and increased the net photosynthetic rate by 66 and 89% under the ambient (AC, ~13 μM CO2) and the HC, respectively. The reduced pO2 enhanced the N2 fixation rate by ~139% under AC and only by 44% under HC, respectively. The N2 fixation quotient, the ratio of N2 fixed per O2 evolved, increased by 143% when pO2 decreased by 75% under the elevated pCO2. Meanwhile, particulate organic carbon and nitrogen quota increased simultaneously under reduced O2 levels, regardless of the pCO2 treatments. Nevertheless, changed levels of O2 and CO2 did not bring about significant changes in the specific growth rate of the diazotroph. Such inconsistency was attributed to the daytime positive and nighttime negative effects of both lowered pO2 and elevated pCO2 on the energy supply for growth. Our results suggest that Trichodesmium decrease its dark respiration by 5% and increase its N2-fixation by 49% and N2-fixation quotient by 30% under future ocean deoxygenation and acidification with 16% decline of pO2 and 138% rise of pCO2 by the end of this century.

Continue reading ‘Deoxygenation enhances photosynthetic performance and increases N2 fixation in the marine cyanobacterium Trichodesmium under elevated pCO2’

Increased food resources help eastern oyster mitigate the negative impacts of coastal acidification

Published 11 April 2023 Science Closed
Tags: , , , , , , , , , , ,

Oceanic absorption of atmospheric CO2 results in alterations of carbonate chemistry, a process coined ocean acidification (OA). The economically and ecologically important eastern oyster (Crassostrea virginica) is vulnerable to these changes because low pH hampers CaCO3 precipitation needed for shell formation. Organisms have a range of physiological mechanisms to cope with altered carbonate chemistry; however, these processes can be energetically expensive and necessitate energy reallocation. Here, the hypothesis that resilience to low pH is related to energy resources was tested. In laboratory experiments, oysters were reared or maintained at ambient (400 ppm) and elevated (1300 ppm) pCO2 levels during larval and adult stages, respectively, before the effect of acidification on metabolism was evaluated. Results showed that oysters exposed to elevated pCO2 had significantly greater respiration. Subsequent experiments evaluated if food abundance influences oyster response to elevated pCO2. Under high food and elevated pCO2 conditions, oysters had less mortality and grew larger, suggesting that food can offset adverse impacts of elevated pCO2, while low food exacerbates the negative effects. Results also demonstrated that OA induced an increase in oyster ability to select their food particles, likely representing an adaptive strategy to enhance energy gains. While oysters appeared to have mechanisms conferring resilience to elevated pCO2, these came at the cost of depleting energy stores, which can limit the available energy for other physiological processes. Taken together, these results show that resilience to OA is at least partially dependent on energy availability, and oysters can enhance their tolerance to adverse conditions under optimal feeding regimes.

Continue reading ‘Increased food resources help eastern oyster mitigate the negative impacts of coastal acidification’

Review of warming and acidification effects to the ecotoxicity of pharmaceuticals on aquatic organisms in the era of climate change

Published 6 April 2023 Science Closed
Tags: , , , , , , , , , , , ,

Highlights

  • Acidification and warming modulates the ecotoxicity of pharmaceuticals.
  • Biochemical, cellular and behavioral biomarkers show a response.
  • Trends of change in acute and chronic toxicity were drug dependent.
  • Acidification modified the toxicity of selected ionizable pharmaceuticals.
  • Bioaccumulation was modified by target effects of global warming.

Abstract

An increase in the temperature and the acidification of the aquatic environment are among the many consequences of global warming. Climate change can also negatively affect aquatic organisms indirectly, by altering the toxicity of pollutants. Models of climate change impacts on the distribution, fate and ecotoxicity of persistent pollutants are now available. For pharmaceuticals, however, as new environmental pollutants, there are no predictions on this issue. Therefore, this paper organizes the existing knowledge on the effects of temperature, pH and both stressors combined on the toxicity of pharmaceuticals on aquatic organisms. Besides lethal toxicity, the molecular, physiological and behavioral biomarkers of sub-lethal stress were also assessed. Both acute and chronic toxicity, as well as bioaccumulation, were found to be affected. The direction and magnitude of these changes depend on the specific pharmaceutical, as well as the organism and conditions involved. Unfortunately, the response of organisms was enhanced by combined stressors. We compare the findings with those known for persistent organic pollutants, for which the pH has a relatively low effect on toxicity. The acid-base constant of molecules, as assumed, have an effect on the toxicity change with pH modulation. Studies with bivalves have been were overrepresented, while too little attention was paid to producers. Furthermore, the limited number of pharmaceuticals have been tested, and metabolites skipped altogether. Generally, the effects of warming and acidification were rather indicated than explored, and much more attention needs to be given to the ecotoxicology of pharmaceuticals in climate change conditions.

Continue reading ‘Review of warming and acidification effects to the ecotoxicity of pharmaceuticals on aquatic organisms in the era of climate change’

No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies

Published 27 January 2023 Science Closed
Tags: , , , , , , , , , , , ,

In a future ocean, dissolved organic carbon (DOC) release by seaweed has been considered a pathway for organic carbon that is not incorporated into growth under carbon dioxide (CO2) enrichment/ocean acidification (OA). To understand the influence of OA on seaweed DOC release, a 21-day experiment compared the physiological responses of three seaweed species, two which operate CO2 concentrating mechanisms (CCMs), Ecklonia radiata (C. Agardh) J. Agardh and Lenormandia marginata (Hooker F. and Harvey) and one that only uses CO2 (non-CCM), Plocamium cirrhosum (Turner) M.J. Wynne. These two groups (CCM and non-CCM) are predicted to respond differently to OA dependent on their affinities for Ci (defined as CO2 + bicarbonate, HCO3−). Future ocean CO2 treatment did not drive changes to seaweed physiology—growth, Ci uptake, DOC production, photosynthesis, respiration, pigments, % tissue carbon, nitrogen, and C:N ratios—for any species, regardless of Ci uptake method. Our results further showed that Ci uptake method did not influence DOC release rates under OA. Our results show no benefit of elevated CO2 concentrations on the physiologies of the three species under OA and suggest that in a future ocean, photosynthetic CO2 fixation rates of these seaweeds will not increase with Ci concentration.

Continue reading ‘No effect of ocean acidification on growth, photosynthesis, or dissolved organic carbon release by three temperate seaweeds with different dissolved inorganic carbon uptake strategies’

Population-specific vulnerability to ocean change in a multistressor environment

Published 26 January 2023 Science Closed
Tags: , , , , , , , , , , , , , ,

Variation in environmental conditions across a species’ range can alter their responses to environmental change through local adaptation and acclimation. Evolutionary responses, however, may be challenged in ecosystems with tightly coupled environmental conditions, where changes in the covariance of environmental factors may make it more difficult for species to adapt to global change. Here, we conduct a 3-month-long mesocosm experiment and find evidence for local adaptation/acclimation in populations of red sea urchins, Mesocentrotus franciscanus, to multiple environmental drivers. Moreover, populations differ in their response to projected concurrent changes in pH, temperature, and dissolved oxygen. Our results highlight the potential for local adaptation/acclimation to multivariate environmental regimes but suggest that thresholds in responses to a single environmental variable, such as temperature, may be more important than changes to environmental covariance. Therefore, identifying physiological thresholds in key environmental drivers may be particularly useful for preserving biodiversity and ecosystem functioning.

Continue reading ‘Population-specific vulnerability to ocean change in a multistressor environment’

Environmental stability and phenotypic plasticity benefit the cold-water coral Desmophyllum dianthus in an acidified fjord

Published 21 July 2022 Uncategorized Closed
Tags: , , , , , , ,

The stratified Chilean Comau Fjord sustains a dense population of the cold-water coral (CWC) Desmophyllum dianthus in aragonite supersaturated shallow and aragonite undersaturated deep water. This provides a rare opportunity to evaluate CWC fitness trade-offs in response to physico-chemical drivers and their variability. Here, we combined year-long reciprocal transplantation experiments along natural oceanographic gradients with an in situ assessment of CWC fitness. Following transplantation, corals acclimated fast to the novel environment with no discernible difference between native and novel (i.e. cross-transplanted) corals, demonstrating high phenotypic plasticity. Surprisingly, corals exposed to lowest aragonite saturation (Ωarag < 1) and temperature (T < 12.0 °C), but stable environmental conditions, at the deep station grew fastest and expressed the fittest phenotype. We found an inverse relationship between CWC fitness and environmental variability and propose to consider the high frequency fluctuations of abiotic and biotic factors to better predict the future of CWCs in a changing ocean.

Continue reading ‘Environmental stability and phenotypic plasticity benefit the cold-water coral Desmophyllum dianthus in an acidified fjord’

Physiological response to seawater pH of the bivalve Abra alba, a benthic ecosystem engineer, is modulated by low pH

Published 19 July 2022 Science Closed
Tags: , , , , ,

Highlights

  • Ocean acidification reduces fitness and condition of a benthic ecosystem engineer.
  • Degree of acidification determines the presence of effects.
  • Ocean acidification decreased the energy intake of Abra alba.
  • Physiological response resulted in higher metabolic losses through increased excretion rates.
  • Physiological changes of benthic engineers likely induce cascading effects on the ecosystem.

Abstract

The presence and behaviour of bivalves can affect the functioning of seafloor sediments through the irrigation of deeper strata by feeding and respiring through siphonal channels. Here, we investigated the physiological response and consecutive impact on functioning and body condition of the white furrow shell Abra alba in three pH treatments (pH = 8.2, pH = 7.9 and pH = 7.7). Although no pH effect on survival was found, lowered respiration and calcification rates, decreased energy intake (lower absorption rate) and increased metabolic losses (increased excretion rates) occurred at pH ∼ 7.7. These physiological responses resulted in a negative Scope for Growth and a decreased condition index at this pH. This suggests that the physiological changes may not be sufficient to sustain survival in the long term, which would undoubtedly translate into consequences for ecosystem functioning.

Continue reading ‘Physiological response to seawater pH of the bivalve Abra alba, a benthic ecosystem engineer, is modulated by low pH’

Effects of elevated pCO2 and temperature on the calcification rate, survival, extrapallial fluid chemistry, and respiration of the Atlantic sea scallop Placopecten magellanicus

Published 13 July 2022 Science Closed
Tags: , , , , , , , ,

Anthropogenic CO2-emission is causing ocean warming and acidification. Understanding how basic physiological processes of marine organisms respond to these stressors is important for predicting their responses to future global change. We examined the effects of elevated pCO2 and temperature (pCO2 = 344–2199 ppm; temperature = 6°C, 9°C, and 12°C) on the calcification rate, extrapallial fluid (EPF) carbonate chemistry, respiration, and survivorship of Atlantic sea scallops (Placopecten magellanicus) in a fully crossed 143-d experiment. Rates of calcification and respiration were inhibited by elevated pCO2, and mortality occurred when elevated pCO2 was accompanied by high-temperature stress. Declines in growth and survivorship were likely caused by external shell dissolution, thermal stress, and hypercapnic reduction of metabolism under elevated pCO2. Concentrations of dissolved inorganic carbon (DIC) and total alkalinity in the EPF increased above seawater concentrations in response to elevated pCO2. EPF pH declined, but did not decline as much as seawater pH, indicating that scallops regulate EPF pH to support calcification. The combination of EPF pH regulation and DIC elevation yielded an increase in EPF [CO2−3] under elevated pCO2 treatments. The combination of low respiration rates, high EPF [CO2−3], and low calcification rates under elevated pCO2 suggests that the impaired calcification arises more from hypercapnic inhibition of metabolic activity and external shell dissolution than from chemically unfavorable conditions in the EPF. These results demonstrate the importance of EPF chemistry for bivalve biomineralization, but show that regulation efforts are insufficient to fully offset the deleterious effects of elevated pCO2 on scallop performance.

Continue reading ‘Effects of elevated pCO2 and temperature on the calcification rate, survival, extrapallial fluid chemistry, and respiration of the Atlantic sea scallop Placopecten magellanicus’

Pelagic and ice-associated microalgae under elevated light and pCO2: contrasting physiological strategies in two Arctic diatoms

Published 13 July 2022 Science Closed
Tags: , , , , , , , , ,

Sea ice retreat, changing stratification, and ocean acidification are fundamentally changing the light availability and physico-chemical conditions for primary producers in the Arctic Ocean. However, detailed studies on ecophysiological strategies and performance of key species in the pelagic and ice-associated habitat remain scarce. Therefore, we investigated the acclimated responses of the diatoms Thalassiosira hyalina and Melosira arctica toward elevated irradiance and CO2 partial pressures (pCO2). Next to growth, elemental composition, and biomass production, we assessed detailed photophysiological responses through fluorometry and gas-flux measurements, including respiration and carbon acquisition. In the pelagic T. hyalina, growth rates remained high in all treatments and biomass production increased strongly with light. Even under low irradiances cells maintained a high-light acclimated state, allowing them to opportunistically utilize high irradiances by means of a highly plastic photosynthetic machinery and carbon uptake. The ice-associated M. arctica proved to be less plastic and more specialized on low-light. Its acclimation to high irradiances was characterized by minimizing photon harvest and photosynthetic efficiency, which led to lowered growth. Comparably low growth rates and strong silification advocate a strategy of persistence rather than of fast proliferation, which is also in line with the observed formation of resting stages under low-light conditions. In both species, responses to elevated pCO2 were comparably minor. Although both diatom species persisted under the applied conditions, their competitive abilities and strategies differ strongly. With the anticipated extension of Arctic pelagic habitats, flexible high-light specialists like T. hyalina seem to face a brighter future.

Continue reading ‘Pelagic and ice-associated microalgae under elevated light and pCO2: contrasting physiological strategies in two Arctic diatoms’

Impact of lowered pH on the morphological, physiological, and microbial community composition of the temperate calcareous sponge, Grantia sp.

Published 1 July 2022 Science Closed
Tags: , , , ,

Global atmospheric carbon dioxide (CO₂) concentrations have been increasing at unprecedented rates since the industrial revolution. The ocean has been acting as a buffer, absorbing CO₂, resulting in rising sea temperature (ocean warming; OW) and lowering its pH (ocean acidification; OA). OA is known to cause reductions in the calcification rates of marine calcifiers, resulting in dissolution of calcium carbonate shells and skeletons. Sponges have important functional and structural roles in marine ecosystems and there is some evidence to suggest that sponges may be “winners” under future ocean climate conditions due to their high level of resilience to OA and OW and the increased availability of space as a result of reductions in more sensitive calcifying species. Although this may be the case for those sponges with skeletons made up of siliceous spicules, little is known about how calcareous sponges, with calcite spicules, may react to OA conditions. This thesis addresses a knowledge gap on how temperate calcareous sponges may respond to OA using Grantia sp. as a model species. A twenty-eight-day experiment with three control (pH 8.0) tanks and three OA (based on IPCC (RCP8.5); pH 7.6) tanks was used to measure changes in sponge size, spicule size, spicule deformation, respiration rate and microbial community structure. I found no signs of corrosion or significant change in area of sponges, however, there was a significant 25% reduction in the spicule size under the projected climate change OA “worst case scenario” conditions, a sign that sponge growth was impacted under stressful external pressure. How this reduction is spicule size will impact the sponge is still unknown. Respiration rates of sponges were not significantly different between the control or treatment sponges, and the microbiome of control and OA sponges did not significantly differ, but they did change significantly over time (T0 compared to T28 (final day of the experiment). The microbiome over time changed with increasing abundance of microbes known to have a role in nutrient cycling and assisting in marine host’s acclimation to new niches with varied environmental conditions. My results suggest that while the physiology of Grantia sp. is not significantly affected by low pH conditions consistent with those predicted for 2100 under worst case climate scenarios, spicules were impacted with treatment sponges having smaller spicules. The consequences and mechanisms resulting in smaller spicules need further investigation. Overall, this study provides evidence that like many demosponges, calcareous sponges may have some resilience to OA impacts.

Continue reading ‘Impact of lowered pH on the morphological, physiological, and microbial community composition of the temperate calcareous sponge, Grantia sp.’

Ocean acidification elicits differential bleaching and gene expression patterns in larval reef coral Pocillopora damicornis under heat stress

Published 29 June 2022 Science Closed
Tags: , , , , , , , , , ,
Graphical abstract

Highlights

  • High temperature induced bleaching and settlement of Pocillopora damicornis larvae.
  • High pCO2 stimulated larval photosynthesis and mitigated symbiont loss at 33 °C.
  • Coral was far more transcriptionally responsive to heat stress than symbionts.
  • Transcriptomic signatures of compromised metabolism and tissue integrity in coral.
  • High pCO2 mediates bleaching and gene expression in P. damicornis larvae under heat.

Abstract

The successful dispersal of coral larvae is vital to the population replenishment and reef recovery and resilience. Despite that this critical early stage is susceptible to ocean warming and acidification, little is known about the responses of coral larvae to warming and acidification across different biological scales. This study explored the influences of elevated temperature (29 °C versus 33 °C) and pCO2 (500 μatm versus 1000 μatm) on brooded larvae of Pocillopora damicornis at the organismal, cellular and gene expression levels. Heat stress caused bleaching, depressed light-enhanced dark respiration, photosynthesis and autotrophy, whereas high pCO2 stimulated photosynthesis. Although survival was unaffected, larvae at 33 °C were ten-times more likely to settle than those at 29 °C, suggesting reduced capacity to disperse and differentiate suitable substrate. Remarkably, heat stress induced greater symbiont loss at ambient pCO2 than at high pCO2, while cell-specific pigment concentrations of symbionts at 33 °C increased twofold under ambient pCO2 relative to high pCO2, suggesting pCO2-dependent bleaching patterns. Considerable increases in activities of host antioxidants superoxide dismutase (SOD) and catalase (CAT) at 33 °C indicated oxidative stress, whereas lipid peroxidation and caspase activities were contained, thereby restraining larval mortality at 33 °C. Furthermore, the coral host mounted stronger transcriptional responses than symbionts. High pCO2 stimulated host metabolic pathways, possibly because of the boosted algal productivity. In contrast, host metabolic processes and symbiont photosystem genes were downregulated at 33 °C. Interestingly, the upregulation of extracellular matrix genes and glycosaminoglycan degradation pathway at 33 °C was more evident under ambient pCO2 than high pCO2, suggesting compromised host tissue integrity that could have facilitated symbiont expulsion and bleaching. Our results provide insights into how coral larvae respond to warming and acidification at different levels of biological organization, and demonstrate that ocean acidification can mediate thermal bleaching and gene expression in coral larvae under heat stress.

Continue reading ‘Ocean acidification elicits differential bleaching and gene expression patterns in larval reef coral Pocillopora damicornis under heat stress’

Synthesized effects of medium-term exposure to seawater acidification and microplastics on the physiology and energy budget of the thick shell mussel Mytilus coruscus

Published 21 June 2022 Science Closed
Tags: , , , ,
Graphical abstract

Highlights

  • Ocean acidification (OA) inhibits most energy related physiological indexes in Mytilus coruscus.
  • OA stress impacts the energy budget of mussels.
  • The mussels are tolerant to Microplastics (MPs) by physiological regulation.
  • Interaction of OA and MPs on the mussels are found in terms of some physiological indexes but not scope for growth.

Abstract

Ocean acidification (OA) and microplastics (MPs) contamination are two results of human excises. In regions like estuarine areas, OA and MPs exposure are happening at the same time. The current research investigated the synthesized effects of OA and MPs exposure for a medium-term duration on the physiology and energy budget of the thick shell mussel Mytilus coruscus. Mussels were treated by six combinations of three MPs levels (0, 10 and 1000 items L−1) × two pH levels (7.3, 8.1) for 21 d. As a result, under pH 7.3, clearance rate (CR), food absorption efficiency (AE), respiration rate (RR), and scope for growth (SFG) significantly decreased, while the fecal organic dry weight ratio (E) significantly increased. 1000 items L−1 MPs led to decrease of CR, E, SFG and increase of AE under pH 8.1. Interactive effects from combination of pH and MPs were found in terms of CR, AE, E and RR, but not for SFG of M. coruscus.

Continue reading ‘Synthesized effects of medium-term exposure to seawater acidification and microplastics on the physiology and energy budget of the thick shell mussel Mytilus coruscus’

Phototrophic sponge productivity may not be enhanced in a high CO2 world

Published 9 June 2022 Science Closed
Tags: , , , , , , , ,

Sponges are major components of benthic communities across the world and have been identified as potential “winners” on coral reefs in the face of global climate change as result of their tolerance to ocean warming and acidification (OA). Previous studies have also hypothesised that photosymbiont-containing sponges might have higher productivity under future OA conditions as a result of photosymbionts having increased access to CO2 and subsequently greater carbon production. Here we test this hypothesis for a widespread and abundant photosymbiont-containing sponge species Lamellodysidea herbacea at a CO2 seep in Papua New Guinea simulating OA conditions. We found seep sponges had relatively higher cyanobacterial abundance, chlorophyll concentrations and symbiont photosynthetic efficiency than non-seep sponges, and a three-fold higher sponge abundance at the seep site. However, while gross oxygen production was the same for seep and non-seep sponges, seep sponge dark respiration rates were higher and instantaneous photosynthesis: respiration (P:R) ratios were lower. We show that while photosymbiont containing sponges may not have increased productivity under OA, they are able to show flexibility in their relationships with microbes and offset increased metabolic costs associated with climate change associated stress.

Continue reading ‘Phototrophic sponge productivity may not be enhanced in a high CO2 world’

Long-term exposure to an extreme environment induces species-specific responses in corals’ photosynthesis and respiration rates

Published 7 June 2022 Science Closed
Tags: , , , , , , , , , , , ,

Extreme reef environments have become useful natural laboratories to investigate physiological specificities of species chronically exposed to future-like climatic conditions. The lagoon of Bouraké in New Caledonia (21°56′56.16′′ S; 125°59′36.82′′ E) is one of the only reef environments studied where the three main climatic stressors predicted to most severely impact corals occur. In this lagoon, temperatures, seawater pHT and dissolved oxygen chronically fluctuate between extreme and close-to-normal values (17.5–33.85 °C, 7.23–7.92 pHT units and 1.87–7.24 mg O2 L−1, respectively). In March 2020, the endosymbiont functions (chl a, cell density and photosynthesis) and respiration rates were investigated in seven coral species from this lagoon and compared with those of corals from an adjacent reference site using hour-long incubations mimicking present-day and future conditions. Corals originating from Bouraké displayed significant differences in these variables compared to reference corals, but these differences were species-specific. Photosynthetic rates of Bouraké corals were all significantly lower than those of reference corals but were partially compensated by higher chlorophyll contents. Respiration rates of the Bouraké corals were either lower or comparable to those of reference corals. Conversely, photosynthesis and respiration rates of most studied species were similar regardless of the incubation conditions, which mimicked either present-day or future conditions. This study supports previous work indicating that no unique response can explain corals’ tolerance to sub-optimal conditions and that a variety of mechanisms will be at play for corals in a changing world.

Continue reading ‘Long-term exposure to an extreme environment induces species-specific responses in corals’ photosynthesis and respiration rates’

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

Published 20 May 2022 Science Closed
Tags: , , , , , , , , , , , , , , , , ,

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.

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

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

Published 19 May 2022 Science Closed
Tags: , , , , , , , , , , ,

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’
  • Reset

Subscribe

OA-ICC Highlights

%d bloggers like this: