Posts Tagged 'laboratory'



Mid-infrared sensor system based on tunable laser absorption spectroscopy for dissolved carbon dioxide analysis in the South China Sea: system-level integration and deployment

System-level integration of a mid-infrared carbon dioxide (CO2) sensor system based on tunable laser absorption spectroscopy (TLAS) was realized for the analysis of dissolved CO2 in seawater employing an interband cascade laser (ICL) centered at 4319 nm and a multi-pass cell (MPC) with an optical path length of 29.8 m. At low measurement pressure of 30 Torr, three absorption lines of 12CO2 were selected to realize different measurement ranges, and a 13CO2 absorption line was targeted for simultaneous isotopic abundance analysis of δ13CO2. The sensor system was compactly integrated into a standalone system with automatic operation for underwater field deployment, and the working process was controlled by a specially-designed electrical system. A gas-liquid separator system was developed for CO2 extraction from water, and a pressure-control mechanism with two operation modes (i.e. static and dynamic mode) was proposed to make the sensor system applicable under deep-sea environment. Series of experiments were carried out in laboratory for performance assessment of the developed sensor system employed for the analysis of dissolved CO2 in water. The sensor was deployed for a field test for natural gas hydrates exploration at an underwater depth of 0−2000 m in the South China Sea, with the sensor operating normally during the deployment.

Continue reading ‘Mid-infrared sensor system based on tunable laser absorption spectroscopy for dissolved carbon dioxide analysis in the South China Sea: system-level integration and deployment’

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’

The impacts of ocean acidification on marine trace gases and the implications for atmospheric chemistry and climate

Surface ocean biogeochemistry and photochemistry regulate ocean–atmosphere fluxes of trace gases critical for Earth’s atmospheric chemistry and climate. The oceanic processes governing these fluxes are often sensitive to the changes in ocean pH (or pCO2) accompanying ocean acidification (OA), with potential for future climate feedbacks. Here, we review current understanding (from observational, experimental and model studies) on the impact of OA on marine sources of key climate-active trace gases, including dimethyl sulfide (DMS), nitrous oxide (N2O), ammonia and halocarbons. We focus on DMS, for which available information is considerably greater than for other trace gases. We highlight OA-sensitive regions such as polar oceans and upwelling systems, and discuss the combined effect of multiple climate stressors (ocean warming and deoxygenation) on trace gas fluxes. To unravel the biological mechanisms responsible for trace gas production, and to detect adaptation, we propose combining process rate measurements of trace gases with longer term experiments using both model organisms in the laboratory and natural planktonic communities in the field. Future ocean observations of trace gases should be routinely accompanied by measurements of two components of the carbonate system to improve our understanding of how in situ carbonate chemistry influences trace gas production. Together, this will lead to improvements in current process model capabilities and more reliable predictions of future global marine trace gas fluxes.

Continue reading ‘The impacts of ocean acidification on marine trace gases and the implications for atmospheric chemistry and climate’

Novel reverse radioisotope labelling experiment reveals carbon assimilation of marine calcifiers under ocean acidification conditions

  1. Ocean acidification by anthropogenic carbon dioxide emissions is projected to depress metabolic and physiological activity in marine calcifiers. To evaluate the sensitivity of marine organisms against ocean acidification, the assimilation of nutrients into carbonate shells and soft tissues must be examined.
  2. We designed a novel experimental protocol, reverse radioisotope labelling, to trace partitioning of nutrients within a single bivalve species under ocean acidification conditions. Injecting CO2 gas, free from radiocarbon, can provide a large contrast between carbon dissolved in the water and the one assimilated from atmosphere. By culturing modern aquifer organisms in acidified seawater, we were able to determine differences in the relative contributions of the end members, dissolved inorganic carbon (DIC) in seawater and metabolic CO2, to shell carbonate and soft tissues.
  3. Under all pCO2 conditions (463, 653, 872, 1,137 and 1,337 μatm), radiocarbon (Δ14C) values of the bivalve Scapharca broughtonii shell were significantly correlated with seawater DIC values; therefore, shell carbonate was derived principally from seawater DIC. The Δ14C results together with stable carbon isotope (δ13C) data suggest that in S. broughtonii shell δ13C may reflect the kinetics of isotopic equilibration as well as end‐member contributions; thus, care must be taken when analysing end‐member contributions by a previous method using δ13C. The insensitivity of S. broughtonii to perturbations in pCO2 up to at least 1,337 µatm indicates that this species can withstand ocean acidification.
  4. Usage of radioisotope to dope for tracer experiments requires strict rules to conduct any operations. Yet, reverse radioisotope labelling proposing in this study has a large advantage and is a powerful tool to understanding physiology of aquifer organisms that can be applicable to various organisms and culture experiments, such as temperature, salinity and acidification experiments, to improve understanding of the proportions of nutrients taken in by marine organisms under changing environments.
Continue reading ‘Novel reverse radioisotope labelling experiment reveals carbon assimilation of marine calcifiers under ocean acidification conditions’

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’


Subscribe to the RSS feed

Powered by FeedBurner

Follow AnneMarin on Twitter

Blog Stats

  • 1,348,090 hits

OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book