Posts Tagged 'laboratory'

Recoverable impacts of ocean acidification on the tubeworm, Hydroides elegans: implication for biofouling in future coastal oceans

Ocean uptake of anthropogenic CO2 causes ocean acidification (OA), which not only decreases the calcification rate, but also impairs the formation of calcareous shells or tubes in marine invertebrates such as the dominant biofouling tubeworm species, Hydroides elegans. This study examined the ability of tubeworms to resume normal tube calcification when returned to ambient pH 8.1 from a projected near-future OA level of pH 7.8. Tubeworms produced structurally impaired and mechanically weaker calcareous tubes at pH 7.8 compared to at pH 8.1, but were able to recover when the pH was restored to ambient levels. This suggests that tubeworms can physiologically recover from the impacts of OA on tube calcification, composition, density, hardness and stiffness when returned to optimal conditions. These results help understanding of the progression of biofouling communities dominated by tubeworms in future oceans with low pH induced by OA.

Continue reading ‘Recoverable impacts of ocean acidification on the tubeworm, Hydroides elegans: implication for biofouling in future coastal oceans’

Elevated pCO2 does not impair performance in autotomised individuals of the intertidal predatory starfish Asterias rubens (Linnaeus, 1758)

Highlights

• Ocean acidification research requires further understanding on the interactions with other stressors.

• We examined the combined effects of pCO2 and arm autotomisation on Asterias rubens.

• Neither stressor affected mortality, growth, arm regeneration, righting time or arm calcium content.

• Lipid content in the pyloric caeca increased in response to elevated pCO2.

• A. rubens appears unaffected by short-term exposure to pCO2 levels predicted for 2100.

Abstract

The impacts of ocean acidification remain less well-studied in starfish compared to other echinoderm groups. This study examined the combined effects of elevated pCO2 and arm regeneration on the performance of the intertidal predatory starfish Asterias rubens, as both are predicted to come at a cost to the individual. A two-way factorial experiment (~400 μatm vs ~1000 μatm; autotomised vs non-automised individuals) was used to examine growth rates, lipid content (pyloric caeca and gonads), and calcium content (body wall) in both intact and regenerating arms, as well as subsequent effects on rate of arm regeneration, righting time (behaviour) and mortality over 120 days. Autotomised individuals tended to show lower (not significant), survival and growth. Elevated pCO2 had no effect on mortality, body growth, arm regeneration, righting time or arm calcium content. Lipid content was higher in the pyloric caeca, but not in the gonads, in response to elevated pCO2 irrespective of autotomisation. The results of the study suggest that adult A. rubens remain unaffected by increased pCO2 and/or arm autotomy for 120 days, although longer term experiments are necessary as the results indicated that survival, growth and calcification may be impaired with longer-term exposure to elevated pCO2.

Continue reading ‘Elevated pCO2 does not impair performance in autotomised individuals of the intertidal predatory starfish Asterias rubens (Linnaeus, 1758)’

Early life stages of Calanus pacificus are neither exposed nor sensitive to low pH waters

We characterized the vertical distribution of Calanus pacificus eggs and larvae and the carbonate chemistry that they are exposed to in Puget Sound, WA. We found that, under stratified conditions, more than 90% of eggs and nauplii stages 1–4 were distributed above the pycnocline, in seawater with pH higher than 7.7. In addition, eggs and larvae from 101 females were reared for 5 days under a range of pH conditions (7.2–8.0) to investigate how pH sensitivity varies among individuals. We observed a slight increase in naupliar survival at pH 7.3 in Individual Brood experiments, while in Mixed Brood experiments, exposure to pH 7.3 led to a small decline in hatching success. In a Split Brood experiment, inter-individual variability among different females’ broods masked pH effects. These results indicate that C. pacificus early life stages are generally tolerant to short-term direct effects of ocean acidification.

Continue reading ‘Early life stages of Calanus pacificus are neither exposed nor sensitive to low pH waters’

Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem

The plea for using more “realistic,” community‐level, investigations to assess the ecological impacts of global change has recently intensified. Such experiments are typically more complex, longer, more expensive, and harder to interpret than simple organism‐level benchtop experiments. Are they worth the extra effort? Using outdoor mesocosms, we investigated the effects of ocean warming (OW) and acidification (OA), their combination (OAW), and their natural fluctuations on coastal communities of the western Baltic Sea during all four seasons. These communities are dominated by the perennial and canopy‐forming macrophyte Fucus vesiculosus—an important ecosystem engineer Baltic‐wide. We, additionally, assessed the direct response of organisms to temperature and pH in benchtop experiments, and examined how well organism‐level responses can predict community‐level responses to the dominant driver, OW. OW affected the mesocosm communities substantially stronger than acidification. OW provoked structural and functional shifts in the community that differed in strength and direction among seasons. The organism‐level response to OW matched well the community‐level response of a given species only under warm and cold thermal stress, that is, in summer and winter. In other seasons, shifts in biotic interactions masked the direct OW effects. The combination of direct OW effects and OW‐driven shifts of biotic interactions is likely to jeopardize the future of the habitat‐forming macroalga F. vesiculosus in the Baltic Sea. Furthermore, we conclude that seasonal mesocosm experiments are essential for our understanding of global change impact because they take into account the important fluctuations of abiotic and biotic pressures.

Continue reading ‘Season affects strength and direction of the interactive impacts of ocean warming and biotic stress in a coastal seaweed ecosystem’

The effects of long-term exposure to low pH on the skeletal microstructure of the sea urchin Heliocidaris erythrogramma

Highlights

• Ocean acidification increases porosity in the sea urchin skeleton.

• Less biomineral is produced.

• Skeleton hardness and elasticity reduced in near future acidification.

• No skeletal etching in near future acidification conditions.

Abstract

Anthropogenic CO2 – driven ocean acidification (OA) is causing a decrease in seawater pH and the saturation state of calcium carbonate minerals, compromising the ability of calcifying species to produce and maintain their skeletons. Sea urchins are ecologically important calcifying species and we investigated the impacts of long-term (9 month) exposure to near-future OA (Ambient – pHNBS 8.01; OA – pHNBS 7.6) on the skeleton microstructure of Heliocidaris erythrogramma using scanning electron microscopy (SEM), micro-computed tomography (μCT) and nanoindentation. SEM revealed that the youngest plates (apical plates) which had likely grown in experimental conditions had larger pores in the OA group (pore surface area ~ 72% larger) compared with those of urchins maintained in ambient pH. High-resolution, μCT 3-D reconstructions of the apical plates revealed that the experimental OA treatment urchins had a ~14% greater porosity and ~17% less biomineral, suggesting an inability to finely regulate skeletogenesis. The mid-test ambital plates established prior to this study did not show any OA associated change in porosity. Nanoindentation of the apical plates indicated that OA reduced skeletal hardness and elasticity. Stereom pore size is a key trait of the sea urchin endoskeleton and increased porosity in H. erythrogramma is likely to impact its biological functions as well as its biomechanical capacity to defend against predation and physical disturbances.

Continue reading ‘The effects of long-term exposure to low pH on the skeletal microstructure of the sea urchin Heliocidaris erythrogramma’

Effects of dissolved oxygen and pH on the expression of a type HBGA-like in pacific oyster

Objective: To study the effects of dissolved oxygen and pH on the expression of A type HBGA-like in pacific oysters. Methods: The HBGAs-like in the pacific oysters were isolated and extracted, and the human HBGAs were used for typing. The A type HBGAs was detected by ELISA method, and the P/N value was calculated. The content changes of A type HBGA-like in the guts and gills of pacific oysters were detected by changing the dissolved oxygen content and pH of seawater under artificial simulation conditions. Results: The HBGA-like of different tissues of oysters were classified, and the A type HBGA-like of gut and gill were selected as the main research type of subsequent experiments; the artificial simulation experiment results showed that the high pH could improve the expression of A type HBGA-like in pacific oysters gills, and the high dissolved oxygen can also improve the expression of A-type HBGA-like in pacific oysters guts. Conclusion: The results were consistent with the phenomenon that the norovirus outbreak usually occur in winter and spring, indicating that the seasonality of norovirus outbreak was correlated with the expression of A type HBGAs-like in oyster.

Continue reading ‘Effects of dissolved oxygen and pH on the expression of a type HBGA-like in pacific oyster’

Antioxidant responses of triangle sail mussel Hyriopsis cumingii exposed to harmful algae Microcystis aeruginosa and high pH

Highlights

• The comprehensive effects of toxic cyanobacteria and high pH on mussels were assessed.

• Interaction between cyanobacteria and high pH on physiological indicator were found.

• Compare to high pH, toxic M. aeruginosa induce more severe oxidative stress response.

• Toxic algae or high pH exposure history showed latent effects on Hyriopsis cumingii.

Abstract

In lakes and reservoirs, harmful algal blooms and high pH have been deemed to be two important stressors related to eutrophication, especially in the case of CO2 depletion caused by dense blooms. However, the effects of these stressors on the economically important shellfish that inhabit these waters are still not well-understood. This study evaluated the combined effects of the harmful algae Microcystis aeruginosa (0%, 50%, and 100% of total dietary dry weight) and high pH (8.0, 8.5 and 9.0) on the antioxidant responses of the triangle sail mussel H. cumingii. The mussels were exposed to algae and high pH for 14 d, followed by a 7-day depuration period. Reactive oxygen species (ROS) in the mussel hemolymph, antioxidant and detoxifying enzymes, such as glutathione-S-transferase (GST), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) in the digestive glands were analyzed during the experimental period. GST, SOD and GPx activity levels and the content of GSH increased following exposure to toxic M. aeruginosa, whereas CAT activity was inhibited. pH showed no significant effects on the immune defense mechanisms and detoxification processes. However, a high pH could cause increased ROS and MDA levels, resulting in oxidative injury. After a 7-day depuration period, exposure to toxic M. aeruginosa or high pH resulted in latent effects for most of the examined parameters. The treatment group exposed to the highest pH (9.0) displayed an increased oxidation state compared with the other pH treatments (8.0 and 8.5) for the same concentrations of toxic M. aeruginosa. The trends observed for ROS, MDA, GPx, GST, SOD and GSH levels indicated that a high density of toxic algae could result in severe and continuous effects on mussel health.

Continue reading ‘Antioxidant responses of triangle sail mussel Hyriopsis cumingii exposed to harmful algae Microcystis aeruginosa and high pH’


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Ocean acidification in the IPCC AR5 WG II

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