Posts Tagged 'physiology'

Ocean acidification, hypoxia and warming impair digestive parameters of marine mussels

Highlights

•Low pH, low DO and high temperature showed drastic effects on digestive enzyme activities.

•Low pH, low DO and high temperature synergistically reduced digestive enzyme activities.

•Lysozyme showed increased and then decreased activities with time.

•Combinations of low pH, low DO and high temperature showed more severe effects on digestive enzymes than single factors.

•Hypoxia and high temperature showed similar effects on digestive enzyme activities.

Abstract

Global change and anthropogenic activities have driven marine environment changes dramatically during the past century, and hypoxia, acidification and warming have received much attention recently. Yet, the interactive effects among these stressors on marine organisms are extremely complex and not accurately clarified. Here, we evaluated the combined effects of low dissolved oxygen (DO), low pH and warming on the digestive enzyme activities of the mussel Mytilus coruscus. In this experiment, mussels were exposed to eight treatments, including two degrees of pH (8.1, 7.7), DO (6, 2 mg/l) and temperature (30 °C and 20 °C) for 30 days. Amylase (AMS), lipase (LPS), trypsin (TRY), trehalase (TREH) and lysozyme (LZM) activities were measured in the digestive glands of mussels. All the tested stress conditions showed significant effects on the enzymatic activities. AMS, LPS, TRY, TREH showed throughout decreased trend in their activities due to low pH, low DO, increased temperature and different combinations of these three stressors with time but LZM showed increased and then decreased trend in their activities. Hypoxia and warming showed almost similar effects on the enzymatic activities. PCA showed a positive correlation among all measured biochemical parameters. Therefore, the fitness of mussel is likely impaired by such marine environmental changes and their population may be affected under the global change scenarios.

Continue reading ‘Ocean acidification, hypoxia and warming impair digestive parameters of marine mussels’

Ocean acidification inhibits initial shell formation of oyster larvae by suppressing the biosynthesis of serotonin and dopamine

Highlights

•5-HT and DA modulate shell formation in oyster larvae through TGF-β smad signaling pathway.

•5-HT and DA trigger the expression of tyrosinase and inhibit the expression of chitinase to form the initial shell.

•OA suppresses the biosynthesis of 5-HT and DA and the activation of TGF-β smad pathway.

•OA subverts the expression patterns of chitinase and tyrosinase and results in the failure of shell formation.

Abstract

Ocean acidification has severely affected the initial shell formation of marine bivalves during their larval stages. In the present study, it was found that dopamine (DA) content in early D-shape larvae was significantly higher than that in trochophore and D-shape larvae, while the serotonin (5-HT) content in early D-shape larvae and D-shape larvae was obviously higher than that in trochophore. Incubation of trochophore with 5-HT or DA could accelerate the formation of calcified shell, and the treatments with selective antagonists of receptors for 5-HT and DA (Cg5-HTR-1 and CgD1DR-1) obviously inhibited the formation of calcified shells. When oyster larvae were subjected to an experimental acidified treatment (pH 7.4), the biosynthesis of 5-HT and DA was inhibited, while the mRNA expression levels of the components in TGF-β pathway were significantly up-regulated in D-shape larvae. Moreover, the phosphorylation of TIR and the translocation of smad4 were hindered upon acidification treatments, and the expression patterns of chitinase and tyrosinase were completely reverted. These results collectively suggested that monoamine neurotransmitters 5-HT and DA could modulate the initial shell formation in oyster larvae through TGF-β smad pathway by regulating the expression of tyrosinase and chitinase to guarantee the chitin synthesis for shell formation. CO2-induced seawater acidification could suppress the biosynthesis of 5-HT and DA, as well as the activation of TGF-β smad pathway, which would subvert the expression patterns of chitinase and tyrosinase and cause the failure of initial shell formation in oyster early D-shape larvae.

Continue reading ‘Ocean acidification inhibits initial shell formation of oyster larvae by suppressing the biosynthesis of serotonin and dopamine’

Nutrient enrichment regulates the growth and physiological responses of Saccharina japonica to ocean acidification

Environmental changes, such as ocean acidification and eutrophication, have created threats to kelp mariculture. In this study, the growth, photosynthesis, respiration and nutrient composition of Saccharina japonica were evaluated at different levels of pCO2 (400 and 800 μL L−1) and nutrients (nutrient-enriched and non-enriched seawater). Elevated pCO2 decreased the relative growth rate (RGR), net photosynthetic rate and contents of tissue carbon and tissue nitrogen under non-enriched nutrient conditions, but it had no significant effect on these parameters under nutrient-enriched conditions. The dark respiration rate was positively affected by elevated pCO2 regardless of the nutrient conditions. However, the C:N was unaffected by elevated pCO2 at both nutrient levels. These results implied that ocean acidification could reduce the production and nutrient contents in the tissues of S. japonica, which was associated with nutrient conditions.

Continue reading ‘Nutrient enrichment regulates the growth and physiological responses of Saccharina japonica to ocean acidification’

Metabolic responses of subtropical microplankton after a simulated deep-water upwelling event suggest a possible dominance of mixotrophy under increasing CO2 levels

In the autumn of 2014, nine large mesocosms were deployed in the oligotrophic subtropical North-Atlantic coastal waters off Gran Canaria (Spain). Their deployment was designed to address the acidification effects of CO2 levels from 400 to 1,400 μatm, on a plankton community experiencing upwelling of nutrient-rich deep water. Among other parameters, chlorophyll a (chl-a), potential respiration (Φ), and biomass in terms of particulate protein (B) were measured in the microplankton community (0.7–50.0 μm) during an oligotrophic phase (Phase I), a phytoplankton-bloom phase (Phase II), and a post-bloom phase (Phase III). Here, we explore the use of the Φ/chl-a ratio in monitoring shifts in the microplankton community composition and its metabolism. Φ/chl-a values below 2.5 μL O2 h−1 (μg chl-a)−1 indicated a community dominated by photoautotrophs. When Φ/chl-a ranged higher, between 2.5 and 7.0 μL O2 h−1 (μg chl-a)−1, it indicated a mixed community of phytoplankton, microzooplankton and heterotrophic prokaryotes. When Φ/chl-a rose above 7.0 μL O2 h−1 (μg chl-a)−1, it indicated a community where microzooplankton proliferated (>10.0 μL O2 h−1 (μg chl-a)−1), because heterotrophic dinoflagellates bloomed. The first derivative of B, as a function of time (dB/dt), indicates the rate of protein build-up when positive and the rate of protein loss, when negative. It revealed that the maximum increase in particulate protein (biomass) occurred between 1 and 2 days before the chl-a peak. A day after this peak, the trough revealed the maximum net biomass loss. This analysis did not detect significant changes in particulate protein, neither in Phase I nor in Phase III. Integral analysis of Φ, chl-a and B, over the duration of each phase, for each mesocosm, reflected a positive relationship between Φ and pCO2 during Phase II [α = 230·10−5 μL O2 h−1 L−1 (μatm CO2)−1 (phase-day)−1, R2 = 0.30] and between chl-a and pCO2 during Phase III [α = 100·10−5 μg chl-a L−1 (μ atmCO2)−1 (phase-day)−1, R2 = 0.84]. At the end of Phase II, a harmful algal species (HAS), Vicicitus globosus, bloomed in the high pCO2 mesocosms. In these mesocosms, microzooplankton did not proliferate, and chl-a retention time in the water column increased. In these V. globosus-disrupted communities, the Φ/chl-a ratio [4.1 ± 1.5 μL O2 h−1 (μg chl-a)−1] was more similar to the Φ/chl-a ratio in a mixed plankton community than to a photoautotroph-dominated one.

Continue reading ‘Metabolic responses of subtropical microplankton after a simulated deep-water upwelling event suggest a possible dominance of mixotrophy under increasing CO2 levels’

Understanding patterns of bivalve vulnerability and resilience to ocean acidification: Insights from field studies, tank experiments and novel physiological studies

Anthropogenic greenhouse gas emissions, including carbon dioxide, are causing an unprecedented rate of global warming. Carbon dioxide emissions are additionally causing ocean acidification; a process that decreases the pH and carbonate saturation state of seawater. Ocean acidification is particularly stressful for marine calcifiers; organisms that build calcium carbonate shells or skeletons. Marine bivalves build calcium carbonate shells that they use as a support for their growing tissues, and as protection from predation. Bivalves are osmoconformers, and have limited mobility, meaning that they are particularly susceptible to the impacts of thermal stress. Bivalve fisheries generate billions of dollars to the US economy in annual revenue, therefore understanding their response to these two global change stressors is crucial for helping the communities that rely on these fisheries plan for global change. The following studies explore the response of commercially important bivalve species to ocean acidification and warming.

Continue reading ‘Understanding patterns of bivalve vulnerability and resilience to ocean acidification: Insights from field studies, tank experiments and novel physiological studies’

Exposure to pet-made microplastics: Particle size and pH effects on biomolecular responses in mussels

Highlights

•PET-MPs are able to induce biochemical stress in mussels.

•LPO and GPx were more effective in detecting the PET-MPs induced stress.

•Biomarkers expression was influenced by the size of PET-MPs.

•L-PET-MPs (0.5–3.0 mm) induced grater effect than other sizes.

•Interaction was recorded among PET-MPs sizes and initial pH (8.0–7.5 units).

Abstract

This study aims to evaluate the expression of biomarkers of oxidative stress (LPO, GPx, AtCh, SOD) in mussels (Mytilus galloprovincialis) following the exposure to suspensions of microparticles irregular shaped fibres of Polyethylene terephthalate of different sizes (small 5–60 μm, S-PET; medium 61–499 μm, M-PET; large 500–3000 μm, L-PET) at a single dose of 0.1 g/L. Mussels were tested under two different starting pH conditions of marine water: standard (8.0) and acidified (7.5). The results obtained from this study show that: i) PET microplastics are able to induce biochemical stress in mussels; ii) among the biomarkers tested, LPO and GPx were more effective in detecting the stress induced by microplastic in both initial pH conditions; iii) the expression of biomarkers was influenced by the size of the microparticle. In particular, greater effects were associated with the largest PET particle tested (0.5–3.0 mm); iv) regarding the effect of pH, in experiments starting from 7.5 pH the animals showed a lower biomarker expression than those starting from 8.0 pH.

Continue reading ‘Exposure to pet-made microplastics: Particle size and pH effects on biomolecular responses in mussels’

Influence of pH on Pb accumulation in the blue mussel, Mytilus edulis

Changes in seawater pH can alter the chemical speciation of waterborne chemical elements, affecting their bioavailability and, consequently, their bioaccumulation in marine organisms. Here, controlled environmental conditions and a 210Pb radiotracer were used to assess the effect of five distinct pH conditions (pHT ranging from 7.16 to 7.94) on the short-term (9 days) accumulation of Pb in the blue mussel, Mytilus edulis. After 9 days of exposure, higher levels of Pb were observed in the soft tissues of mussels maintained in the lower pH conditions, while Pb levels accumulated by mussel shells showed no difference across pH conditions. These results suggest that pH decreases such as those predicted by ocean acidification scenarios could enhance Pb contamination in marine organisms, with potential subsequent contamination and effect risks for human consumers.

Continue reading ‘Influence of pH on Pb accumulation in the blue mussel, Mytilus edulis’


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Ocean acidification in the IPCC AR5 WG II

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