Posts Tagged 'laboratory'

Adult exposure to ocean acidification and warming remains beneficial for oyster larvae following starvation

Climate change is expected to warm and acidify oceans and alter the phenology of phytoplankton, creating a mismatch between larvae and their food. Transgenerational plasticity (TGP) may allow marine species to acclimate to climate change; however, it is expected that this may come with elevated energetic demands. This study used the oysters, Saccostrea glomerata and Crassostrea gigas, to test the effects of adult parental exposure to elevated pCO2 and temperature on larvae during starvation and recovery. It was anticipated that beneficial effects of TGP will be limited when larvae oyster are starved. Transgenerational responses and lipid reserves of larvae were measured for 2 weeks. Larvae of C. gigas and S. glomerata from parents exposed to elevated pCO2 had greater survival when exposed to elevated CO2, but this differed between species and temperature. For S. glomerata, survival of larvae was greatest when the conditions experienced by larvae matched the condition of their parents. For C. gigas, survival of larvae was greater when parents and larvae were exposed to elevated pCO2. Larvae of both species used lipids when starved. The total lipid content was dependent on parental exposure and temperature. Against expectations, the beneficial TGP responses of larvae remained, despite starvation.

Continue reading ‘Adult exposure to ocean acidification and warming remains beneficial for oyster larvae following starvation’

Viral-mediated microbe mortality modulated by ocean acidification and eutrophication: consequences for the carbon fluxes through the microbial food web

Anthropogenic carbon emissions are causing changes in seawater carbonate chemistry including a decline in the pH of the oceans. While its aftermath for calcifying microbes has been widely studied, the effect of ocean acidification (OA) on marine viruses and their microbial hosts is controversial, and even more in combination with another anthropogenic stressor, i.e., human-induced nutrient loads. In this study, two mesocosm acidification experiments with Mediterranean waters from different seasons revealed distinct effects of OA on viruses and viral-mediated prokaryotic mortality depending on the trophic state and the successional stage of the plankton community. In the winter bloom situation, low fluorescence viruses, the most abundant virus-like particle (VLP) subpopulation comprising mostly bacteriophages, were negatively affected by lowered pH with nutrient addition, while the bacterial host abundance was stimulated. High fluorescence viruses, containing cyanophages, were stimulated by OA regardless of the nutrient conditions, while cyanobacteria of the genus Synechococcus were negatively affected by OA. Moreover, the abundance of very high fluorescence viruses infecting small haptophytes tended to be lower under acidification while their putative hosts’ abundance was enhanced, suggesting a direct and negative effect of OA on viral–host interactions. In the oligotrophic summer situation, we found a stimulating effect of OA on total viral abundance and the viral populations, suggesting a cascading effect of the elevated pCO2 stimulating autotrophic and heterotrophic production. In winter, viral lysis accounted for 30 ± 16% of the loss of bacterial standing stock per day (VMMBSS) under increased pCO2 compared to 53 ± 35% in the control treatments, without effects of nutrient additions while in summer, OA had no significant effects on VMMBSS (35 ± 20% and 38 ± 5% per day in the OA and control treatments, respectively). We found that phage production and resulting organic carbon release rates significantly reduced under OA in the nutrient replete winter situation, but it was also observed that high nutrient loads lowered the negative effect of OA on viral lysis, suggesting an antagonistic interplay between these two major global ocean stressors in the Anthropocene. In summer, however, viral-mediated carbon release rates were lower and not affected by lowered pH. Eutrophication consistently stimulated viral production regardless of the season or initial conditions. Given the relevant role of viruses for marine carbon cycling and the biological carbon pump, these two anthropogenic stressors may modulate carbon fluxes through their effect on viruses at the base of the pelagic food web in a future global change scenario.

Continue reading ‘Viral-mediated microbe mortality modulated by ocean acidification and eutrophication: consequences for the carbon fluxes through the microbial food web’

The effects on low pH on sea urchin larval survivorship and development

In recent decades, increasing atmospheric CO2 levels have contributed to the acidification of the world’s oceans. Seawater absorbs CO2 from the atmosphere, which, through a series of chemical reactions, causes an increase in free hydrogen ions and a subsequent decrease in carbonate ions. This adversely affects marine organisms, including sea urchins, since carbonate is critical for building calcium carbonate structures such as shells, without which organisms can die. Declines in urchin populations can have ecological and economic effects, as urchins play critical roles in maintaining ecological balance in marine habitats and are important commercially harvested invertebrates. Larval marine organisms are particularly vulnerable, and increased deformities and mortality are expected in more acidic environments. Therefore, we exposed green sea urchin (Lytechinus variegatus) larvae to different pH levels and examined the effects on development and mortality. Fertilized eggs were reared in seawater with environmentally realistic pH values ranging from pH 7.8 to pH 8.2 (normal seawater), and a larval sample from each treatment was collected every 24 hours for 7 – 10 days. Mortality was documented by counting dead larvae, and development was assessed by comparing morphology among the control and treatment groups. In general, both mortality and morphological abnormalities showed inverse correlations with pH, with the highest mortality rate and most severe abnormalities occurring in larvae exposed to the lowest pH seawater. Larval development was also somewhat delayed in urchin larvae exposed to low pH seawater. These results suggest that acidic seawater, at pH values currently found in the world’s oceans, can adversely affect sea urchin larval development, which can, in turn, have negative ecological and economic consequences.

Continue reading ‘The effects on low pH on sea urchin larval survivorship and development’

Effects of extra feeding combined with ocean acidification and increased temperature on the carbon isotope values (δ13C) in the mussel shell

Highlights

  • Ocean acidification, OA, increased metabolic carbon uptake in mussel shell calcite.
  • Additive effects of increased temperature and extra feeding on carbon uptake.
  • Mussels alter their biomineralisation pathways relating to food carbon uptake.
  • Metabolic carbon uptake is 7–11% higher in the shell aragonite compared to calcite.
  • Molluscs with different composites may alter biomineralisation under OA.

Abstract

Ocean acidification (OA) and global warming present future challenges for shell producing organisms such as mussels through reduction in the carbonate available to produce shells in these and other valuable aquaculture species. Molluscs control their shell growth through biomineralisation, but the response of the mechanisms behind biomineralisation to OA conditions are relatively unknown. It is unclear how much carbon is taken into the shell from the environment compared to the uptake through the food source. Shell production is energetically costly to molluscs and metabolic processes and energetic partitioning may affect their ability to perform the underlying mechanisms of biomineralisation under OA. It is possible that additional food consumption might alleviate some impacts caused by acidification. We assessed the ability of extra feeding to alter the impacts of OA and increased temperatures on adult Mytilus edulis. Carbon isotopes (δ13C) were used to examine the change in biomineralisation pathway in mussels. OA did not alter the δ13C directly in separate analyses of the shell calcite and aragonite layers, mantle tissue and extrapallial fluid. However, ambient treatments with increased temperatures altered the mussel biomineralisation pathway in the shell calcite using CO32− instead of HCO3 as the main source of carbon. The proportion of metabolic carbon uptake into the mussel shell calcite layer increased under OA, with additive effects when exposed to increased temperatures and extra feeding. The proportion of metabolic carbon uptake is higher (7%–11%) in the shell aragonite layer compared to calcite, under ambient treatments. OA initially reduced the metabolic carbon uptake into the shell aragonite, but after a period of 4-months with extra feeding, the mussels were able to adjust their metabolic carbon uptake to a level experienced under ambient treatments. This indicates that an abundance of food resources may enable changes in mussel biomineralisation pathways to compensate for any decrease in seawater inorganic carbon associated with OA. The impact of OA on phytoplankton varies from species to species, changing the structure of the community which could provide sufficient food resources to maintain metabolic carbon uptake for mussel shell growth. This study of δ13C isotopic values has identified changes in biomineralisation pathway relating to the mussel metabolic carbon uptake from their food source, with varying results for the aragonite and calcite shell polymorphs. The implications of these findings suggest that some bivalve species with different shell composites may cope better under OA than others, demanding further study into species-specific biomineralisation pathways.

Continue reading ‘Effects of extra feeding combined with ocean acidification and increased temperature on the carbon isotope values (δ13C) in the mussel shell’

Ocean acidification but not elevated spring warming threatens a European Seas predator

Highlights

  • Treatments in marine climate research often ignore important, natural variation
  • Fish embryos were exposed to stable versus warming temperatures (T) and high pCO2
  • Development, hatching and metabolism of a predatory fish (garfish) were examined
  • Increased spring warming benefitted garfish but stable high T and pCO2 were lethal
  • Allospecific prey of garpike have adapted suggesting future, trophodynamic change

Abstract

Ocean acidification has the potential to negatively affect marine ecosystems by influencing the development and metabolism of key members of food webs. The garfish, Belone belone, is an ecologically important predator in European regional seas and it remains unknown how this species will be impacted by projected changes in climate. We artificially fertilized and reared garfish embryos until hatch at present (400 μatm) and future (1300 μatm) pCO2 levels within three temperature treatments, i.e. two daily warming regimes and one constant high temperature (17°C). For the two warming treatments, embryos were fertilized at 13°C and experienced 0.1 or 0.3°C/day warming. The 0.1°C/day treatment served as control: 13°C was the in situ temperature of parental fish in the Southwest Baltic Sea and 0.1°C/day is the average warming rate experienced by embryos of this population in nature. Survival was drastically reduced at both future pCO2 and at the constant high temperature while the highest survival in any treatment was observed at 0.3°C/day warming. The proportion of embryos with morphological deformities increased with elevated pCO2 but not temperature. Hatch characteristics and physiological measures such as heart rate and critical thermal ranges, however, were not affected by pCO2 but were influenced by temperature. Our results suggest that garfish in the Baltic Sea will benefit from projected increased rates of spring warming but not the concomitant increase in pCO2. Previous studies on the impacts of ocean acidification on resident fishes in the Baltic Sea indicate that this piscivorous fish is at higher risk compared to its prey which may have broader implications for the future trophodynamic structure and function of the coastal food web.

Continue reading ‘Ocean acidification but not elevated spring warming threatens a European Seas predator’

Combined effect of microplastics and global warming factors on early growth and development of the sea urchin (Paracentrotus lividus)

Highlights

  • This work focusses on the effect of a multi-stressor environment in sea urchin.
  • Embryo-larval bioassays were used to determine growth and morphometric parameters.
  • A lower water pH (7.6) reduced larval growth and caused deformities.
  • Microplastics aggravate the effect of water acidification in sea urchin larvae.
  • High temperatures caused an additional stress and reduced larvae stomach volume.

Abstract

The aim of this work was to estimate the potential risk of the combined effect of global change factors (acidification, temperature increase) and microplastic (MP) pollution on the growth and development of the sea urchin P. lividus. Embryo-larval bioassays were conducted to determine growth and morphology after 48 h of incubation with MP (1000 and 3000 particles/mL); with filtered sea water at pH = 7.6; and with their combinations. A second experiment was conducted to study the effect of pH and MP in combination with a temperature increase of 4 °C compared to control (20 °C). We found that the inhibition of growth in embryos reared at pH = 7.6 was around 75%. Larvae incubated at 3000 MP particles/mL showed a 20% decrease in growth compared to controls. The exposure to MP also induced an increase in the postoral arm separation or rounded vertices. The combined exposure to a pH 7.6 and MP caused a significant decrease of larval growth compared to control, to MP and to pH 7.6 treatments. Morphological alterations were observed in these treatments, including the development of only two arms. Increasing the temperature resulted in an increased growth in control, in pH 7.6 and pH 7.6 + MP3000 treatments, but the relative stomach volume decreased. However, when growth parameters were expressed per Degree-Days the lower growth provoked by the thermal stress was evidenced in all treatments. In this work we demonstrated that MP could aggravate the effect of a decreased pH and that an increase in water temperature generated an additional stress on P. lividus larvae, manifested in a lower growth and an altered development. Therefore, the combined stress caused by ocean warming, ocean acidification, and microplastic pollution, could threaten sea urchin populations leading to a potential impact on coastal ecosystems.

Continue reading ‘Combined effect of microplastics and global warming factors on early growth and development of the sea urchin (Paracentrotus lividus)’

Risks to the stability of coral reefs in the South China Sea: an integrated biomarker approach to assess the physiological responses of Trochus niloticus to ocean acidification and warming

Highlights

  • OA and OW have deleterious effects on the fitness of T. niloticus.
  • Co-exposure of OA and OW is the most stressful condition.
  • OA and OW may adversely affect population replenishment of T. niloticus.

Abstract

Scientific researches have clearly indicated that ocean acidification and warming poses serious threats to coral reef ecosystems. In coral reef ecosystems, herbivorous gastropods have an important function in maintaining the stability of the ecosystem due to controlling the abundance and growth of macroalgal, which compete for nutrients and space with coral. However, limited knowledge is available on the physiological responses of the specific keystone species to the increased ocean acidity and thermal stress. In this study, we evaluated the effects of ocean acidification (OA) and warming (OW) on an herbivorous gastropod Trochus niloticus commonly found on intertidal and shallow subtidal coral reefs in the South China Sea, on the aspect of immune responses (total hemocyte counts, reactive oxygen species level and apoptosis rate), oxidative stress (lipid peroxidation level, antioxidant enzyme activities), neurotoxicity (acetylcholinesterase activity), and energy metabolism (respiration rate and cellular energy allocation), after a 28-days exposure experiment to acidic (pH 7.6) and/or thermal (30 °C) seawater. Our results demonstrated that both OA and OW could lead to physiological disturbances of the herbivorous top-shells, including impaired immune functions and oxidative balance, neurotoxicity, and disorder of energy metabolism. Furthermore, results of integrated biomarker response (IBR) confirmed that the overall fitness of T. niloticus were deleteriously impacted by OA and OW, and were more stressed under the co-exposure condition. These results indicated that increased acidity and temperature in the future ocean might impair the viability of T. niloticus in the long-run, which will indulge the proliferation of macroalgae and lead to degradation of the coral reef ecosystem.

Continue reading ‘Risks to the stability of coral reefs in the South China Sea: an integrated biomarker approach to assess the physiological responses of Trochus niloticus to ocean acidification and warming’

Transgenerational plasticity responses of oysters to ocean acidification differ with habitat

Transgenerational plasticity (TGP) has been identified as a critical mechanism of acclimation which may buffer marine organisms against climate change, yet whether the TGP response of marine organisms is altered depending on their habitat is unknown. Many marine organisms are found in intertidal zones where they experience episodes of emersion daily as the tide rises and recedes. During episodes of emersion, the accumulation of metabolic carbon dioxide (CO2) leads to hypercapnia for many species. How this metabolic hypercapnia impacts the TGP response of marine organisms to climate change is unknown as all previous transgenerational studies have been done under subtidal conditions, where parents are constantly immersed. Herein, we assess the capacity of the ecologically and economically important oyster, Saccostrea glomerata to acclimate to elevated CO2 dependent on habitat, across its vertical distribution, from the subtidal to intertidal zone. Tidal habitat altered both the existing tolerance and transgenerational response of S. glomerata to elevated CO2. Overall, larvae from parents conditioned in an intertidal habitat had a greater existing tolerance to elevated CO2 than larvae from parents conditioned in a subtidal habitat but had a lower capacity for beneficial TGP following parental exposure to elevated CO2. Our results suggest that the transgenerational plasticity responses of marine species will not be uniform across their distribution and highlights the need to consider the habitat of a species when assessing TGP responses to climate change stressors.

Continue reading ‘Transgenerational plasticity responses of oysters to ocean acidification differ with habitat’

Impact of dust addition on the metabolism of Mediterranean plankton communities and carbon export under present and future conditions of pH and temperature

Although atmospheric dust fluxes from arid as well as human-impacted areas represent a significant source of nutrients to surface waters of the Mediterranean Sea, studies focusing on the evolution of the metabolic balance of the plankton community following a dust deposition event are scarce and none were conducted in the context of projected future levels of temperature and pH. Moreover, most of the experiments took place in coastal areas. In the framework of the PEACETIME project, three dust-addition perturbation experiments were conducted in 300-L tanks filled with surface seawater collected in the Tyrrhenian Sea (TYR), Ionian Sea (ION) and in the Algerian basin (FAST) onboard the R/V “Pourquoi Pas?” in late spring 2017. For each experiment, six tanks were used to follow the evolution of chemical and biological stocks, biological activity and particle export. The impacts of a dust deposition event simulated at their surface were followed under present environmental conditions and under a realistic climate change scenario for 2100 (ca. +3 °C and −0.3 pH units). The tested waters were all typical of stratified oligotrophic conditions encountered in the open Mediterranean Sea at this period of the year, with low rates of primary production and a metabolic balance towards net heterotrophy. The release of nutrients after dust seeding had very contrasting impacts on the metabolism of the communities, depending on the station investigated. At TYR, the release of new nutrients was followed by a negative impact on both particulate and dissolved 14C-based production rates, while heterotrophic bacterial production strongly increased, driving the community to an even more heterotrophic state. At ION and FAST, the efficiency of organic matter export due to mineral/organic aggregation processes was lower than at TYR likely related to a lower quantity/age of dissolved organic matter present at the time of the seeding. At these stations, both the autotrophic and heterotrophic community benefited from dust addition, with a stronger relative increase in autotrophic processes observed at FAST. Our study showed that the potential positive impact of dust deposition on primary production depends on the initial composition and metabolic state of the investigated community. This potential is constrained by the quantity of nutrients added in order to sustain both the fast response of heterotrophic prokaryotes and the delayed one of primary producers. Finally, under future environmental conditions, heterotrophic metabolism was overall more impacted than primary production, with the consequence that all integrated net community production rates decreased with no detectable impact on carbon export, therefore reducing the capacity of surface waters to sequester anthropogenic CO2.

Continue reading ‘Impact of dust addition on the metabolism of Mediterranean plankton communities and carbon export under present and future conditions of pH and temperature’

Partner preference in the intertidal: possible benefits of ocean acidification to sea anemone-algal symbiosis

Ocean acidification (OA) threatens many marine species and is projected to become more severe over the next 50 years. Areas of the Salish Sea and Puget Sound that experience seasonal upwelling of low pH water are particularly susceptible to even lower pH conditions. While ocean acidification literature often describes negative impacts to calcifying organisms, including economically important shellfish, and zooplankton, not all marine species appear to be
threatened by OA. Photosynthesizing organisms, in particular, may benefit from increased levels of CO2. The aggregating anemone (Anthopleura elegantissima), a common intertidal organism throughout the northeast Pacific, hosts two photosynthetic symbionts: Symbiodinium muscatinei (a dinoflagellate) and Elliptochloris marina (a chlorophyte). The holobiont, therefore, consists of both a cnidarian host and a photosymbiont that could be affected differently by the changing levels of environmental CO2. To determine the effects of OA on this important marine organism, A. elegantissima in each of four symbiotic conditions (hosting S. muscatinei, hosting E. marina, hosting mixed symbiont assemblages, or symbiont free) were subjected to one of three pCO2 levels (800 ppm, 1200 ppm, or 1800 ppm) of OA for 10 weeks. At regular intervals, gross photosynthesis and density of the symbionts, respiration rate of the hosts, levels of reactive oxygen species (ROS) in the host, and percent of organic carbon received by the host from the symbiont (CZAR) were measured. Over the 10-week period of the experiment, the densities of symbionts responded differently to an increase in pCO2, increasing in anemones hosting S. muscatinei but decreasing for those hosting E. marina. Similarly, anemones of mixed symbiont complement that started with approximately 50% of each symbiont type shifted toward a higher percentage of S. muscatinei with higher pCO2. Both gross photosynthesis and dark respiration were significantly affected by pCO2 and symbiont state, though we cannot say that the symbiontsv responded differently to increased OA. Symbiont state was a significant predictor for ROS concentration, with greatest levels seen in anemones hosting E. marina and for CZAR score, with greatest levels in anemones hosting S. muscatinei, our linear models did not reveal pCO2 as a significant factor in these responses. Together, these results suggest that S. muscatinei may benefit from elevated pCO2 levels and that A. elegantissima hosting that symbiont may have a competitive advantage under some future scenarios of ocean acidification.

Continue reading ‘Partner preference in the intertidal: possible benefits of ocean acidification to sea anemone-algal symbiosis’

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