Posts Tagged 'laboratory'

The pH dependency of the boron isotopic composition of diatom opal (Thalassiosira weissflogii) (update)

The high-latitude oceans are key areas of carbon and heat exchange between the atmosphere and the ocean. As such, they are a focus of both modern oceanographic and palaeoclimate research. However, most palaeoclimate proxies that could provide a long-term perspective are based on calcareous organisms, such as foraminifera, that are scarce or entirely absent in deep-sea sediments south of 50 S in the Southern Ocean and north of 40 N in the North Pacific. As a result, proxies need to be developed for the opal-based organisms (e.g. diatoms) found at these high latitudes, which dominate the biogenic sediments recovered from these regions. Here we present a method for the analysis of the boron (B) content and isotopic composition (δ11B) of diatom opal. We apply it for the first time to evaluate the relationship between seawater pH, δ11B and B concentration ([B]) in the frustules of the diatom Thalassiosira weissflogii, cultured across a range of carbon dioxide partial pressure (pCO2) and pH values. In agreement with existing data, we find that the [B] of the cultured diatom frustules increases with increasing pH (Mejía et al., 2013). δ11B shows a relatively well defined negative trend with increasing pH, completely distinct from any other biomineral previously measured. This relationship not only has implications for the magnitude of the isotopic fractionation that occurs during boron incorporation into opal, but also allows us to explore the potential of the boron-based proxies for palaeo-pH and palaeo-CO2 reconstruction in high-latitude marine sediments that have, up until now, eluded study due to the lack of suitable carbonate material.

Continue reading ‘The pH dependency of the boron isotopic composition of diatom opal (Thalassiosira weissflogii) (update)’

Transgenerational regulation of cbln11 gene expression in the olfactory rosette of the European sea bass (Dicentrarchus labrax) exposed to ocean acidification


Cbln11 mRNA is mainly expressed in the olfactory rosettes and in the gills of European sea bass.

Cbln11 mRNA expression is localized in the non-sensory epithelium of the olfactory rosettes.

•Long term exposure to ocean acidification induces a stimulation of cbln11 mRNA expression in the olfactory rosette of European sea bass.

•Ocean acidification-induced stimulation of cbln11 mRNA expression suggests a regulation of innate immune function.


Elevated amounts of atmospheric CO2 are causing ocean acidification (OA) that may affect marine organisms including fish species. While several studies carried out in fish revealed that OA induces short term dysfunction in sensory systems including regulation of neurons activity in olfactory epithelium, information on the effects of OA on other physiological processes and actors is scarcer. In the present study we focused our attention on a European sea bass (Dicentrarchus labrax) sghC1q gene, a member of the C1q-domain-containing (C1qDC) protein family. In vertebrates, C1qDC family includes actors involved in different physiological processes including immune response and synaptic organization. Our microsynteny analysis revealed that this sghC1q gene is the orthologous gene in European sea bass to zebrafish (Danio rerio) cbln11 gene. We cloned the full length cbln11 mRNA and identified the different domains (the signal peptide, the coiled coil region and the globular C1q domain) of the deduced protein sequence. Investigation of mRNA expression by qPCR and in situ hybridization revealed that cbln11gene is especially expressed in the non-sensory epithelium of the olfactory rosette at larval and adult stages. The expression of cbln11 mRNA was analysed by qPCR in the first generation (F0) of European sea bass broodstock exposed since larval stages to water pH of 8.0 (control) or 7.6 (predicted for year 2100) and in their offspring (F1) maintained in the environmental conditions of their parents. Our results showed that cbln11 mRNA expression level was lower in larvae exposed to OA then up-regulated at adult stage in the olfactory rosette of F0 and that this up-regulation is maintained under OA at larval and juvenile stages in F1. Overall, this work provides evidence of a transgenerational inheritance of OA-induced up-regulation of cbln11 gene expression in European sea bass. Further studies will investigate the potential immune function of cbln11 gene and the consequences of these regulations, as well as the possible implications in terms of fitness and adaptation to OA in European sea bass.

Continue reading ‘Transgenerational regulation of cbln11 gene expression in the olfactory rosette of the European sea bass (Dicentrarchus labrax) exposed to ocean acidification’

Response of the red algae Pyropia yezoensis grown at different light intensities to CO2-induced seawater acidification at different life cycle stages


•Elevated CO2 enhanced conchocelis growth regardless of light intensity.

•Elevated CO2 enhanced thallus growth at high light but reduced it at low light.

•Elevated CO2 did not affect conchocelis respiration rate at either light intensity.

•Elevated CO2 increased thallus respiration rate at each light intensity.


Increasing CO2 levels in the surface water of oceans are expected to decrease oceanic pH and lead to seawater acidification. The responses of macroalgaea to this acidification of coastal waters have been studied in detail; however, most reports have focused on the adult stage only, while ignoring other life cycle stages. In this study, the economically important seaweed species Pyropia yezoensis was cultured under two CO2 concentrations (ambient CO2: 400 μatm; elevated CO2: 1000 μatm) and two light intensities (low light intensity: 80 μmol photons m−2 s−1; and high light intensity: 240 μmol photons m−2 s−1). The effects on the growth and photosynthetic performance of P. yezoensis were explored at different life cycle stages. Relative growth rates were significantly elevated at the conchocelis stage under high light intensity and elevated CO2 concentration. Moreover, the Pmax of P. yezoensis was also increased under high light intensity. However, this positive effect inversed at the thallus stage. The relative growth rate, relative electron transport rate (rETR), and net photosynthetic rate decreased at the thallus stage in response to high CO2 concentration. Under low light intensity, elevated CO2 concentration significantly increased the relative growth rates of conchocelis and thallus stages. These were 269% and 45% higher at elevated CO2 concentration compared with ambient CO2 concentrations, respectively. The Chl a and phycoerythrin levels were also higher under elevated CO2 level at the conchocelis stage. However, the rETR for the thallus stage was elevated under low light. This suggests that seawater acidification could positively affect algae at low light conditions (especially at the conchocelis stage). Different growth stages of P. yezoensis may respond differently to seawater acidification and changes of light intensity. Thalli growth stage, stocking density, and seawater depth should be considered in different areas to optimize the primary production of macroalgae.

Continue reading ‘Response of the red algae Pyropia yezoensis grown at different light intensities to CO2-induced seawater acidification at different life cycle stages’

Differential gene expression patterns related to lipid metabolism in response to ocean acidification in larvae and juveniles of Atlantic cod


•Larvae upregulate genes associated with fatty acid and glycogen synthesis under moderate ocean acidification (OA)

•Larvae under high levels of OA fail to regulate

•Dysfunctional metabolism and stress associated with pathologies in internal organs

•Juveniles do not differentially regulate genes under OA, associated with higher resilience and lack of physiological response to OA as a stressor at this stage


Elevated environmental carbon dioxide (pCO2) levels have been found to cause organ damage in the early life stages of different commercial fish species, including Atlantic cod (Gadus morhua). To illuminate the underlying mechanisms causing pathologies in the intestines, the kidney, the pancreas and the liver in response to elevated pCO2, we examined related gene expression patterns in Atlantic cod reared for two months under three different pCO2 regimes: 380 μatm (control), 1800 μatm (medium) and 4200 μatm (high). We extracted RNA from whole fish sampled during the larval (32 dph) and early juvenile stage (46 dph) for relative expression analysis of 18 different genes related to essential metabolic pathways. At 32 dph, larvae subjected to the medium treatment displayed an up-regulation of genes mainly associated with fatty acid and glycogen synthesis (GYS2, 6PGL, ACoA, CPTA1, FAS and PPAR1b). Larvae exposed to the high pCO2 treatment upregulated fewer but similar genes (6PGL, ACoA and PPAR1b,). These data suggest stress-induced alterations in the lipid and fatty acid metabolism and a disrupted lipid homeostasis in larvae, providing a mechanistic link to the findings of lipid droplet overload in the liver and organ pathologies. At 46 dph, no significant differences in gene expression were detected, confirming a higher resilience of juveniles in comparison to larvae when exposed to elevated pCO2 up to 4200 μatm.

Continue reading ‘Differential gene expression patterns related to lipid metabolism in response to ocean acidification in larvae and juveniles of Atlantic cod’

The Olympia oyster (Ostrea lurida) at risk for local extinction: addressing climate change impacts

The Olympia oyster is native to San Francisco Bay (Ostrea lurida Carpenter 1864) (Barrett 1963). Their habitat ranges from Sitka, Alaska to Baja, California (Dall 1914). Historically, the Olympia oyster was abundant throughout the Pacific Northwest. However, their population has declined over the last few centuries due to anthropogenic influences, urbanization, and erosion (Groth and Rumrill 2009; McGraw 2009) Native Americans, pioneers, and gold miners consumed Olympia oysters which reduced the population. Remnants of native oyster shell middens around the Bay are evidence of the abundance prior to Spanish settlement. (Groth and Rumrill 2009; Coastal Conservancy and NOAA 2010). Over-harvesting reduced the oyster population and provided an opportunity to bring in non-native oysters due to the demand for oyster meat. Approximately 150 tons of oyster meat was processed (15% of the total oyster harvest represented the native oyster) during the height of the oyster industry which was from the late 1880s until 1904. (Barrett 1963). The resulting demand provided an opportunity to introduce the non-native Atlantic oyster in the San Francisco Bay, which further reduced the population of the native Olympia oyster as the nonnative Atlantic oyster was more significant in size and competed for space (Barrett 1963). Nonnative species of oysters such as the Eastern oyster from 1869-1940 and Pacific oysters from 1928-1950 were introduced into the San Francisco Bay. Ship ballasts brought in non-native species and fouling species (Ruiz et al. 2011), which preyed on the native oyster. However, the native oyster continues to live in the San Francisco Bay.

Continue reading ‘The Olympia oyster (Ostrea lurida) at risk for local extinction: addressing climate change impacts’

Warming and acidification threaten glass sponge Aphrocallistes vastus pumping and reef formation

The glass sponge Aphrocallistes vastus contributes to the formation of large reefs unique to the Northeast Pacific Ocean. These habitats have tremendous filtration capacity that facilitates flow of carbon between trophic levels. Their sensitivity and resilience to climate change, and thus persistence in the Anthropocene, is unknown. Here we show that ocean acidification and warming, alone and in combination have significant adverse effects on pumping capacity, contribute to irreversible tissue withdrawal, and weaken skeletal strength and stiffness of A. vastus. Within one month sponges exposed to warming (including combined treatment) ceased pumping (50–60%) and exhibited tissue withdrawal (10–25%). Thermal and acidification stress significantly reduced skeletal stiffness, and warming weakened it, potentially curtailing reef formation. Environmental data suggests conditions causing irreversible damage are possible in the field at +0.5 °C above current conditions, indicating that ongoing climate change is a serious and immediate threat to A. vastus, reef dependent communities, and potentially other glass sponges.

Continue reading ‘Warming and acidification threaten glass sponge Aphrocallistes vastus pumping and reef formation’

External pH modulation during the growth of Vibrio tapetis , the etiological agent of Brown Ring Disease

Brown Ring Disease (BRD) is an infection of the Manila clam Ruditapes philippinarum due to the pathogen Vibrio tapetis . During BRD, clams are facing immunodepression and shell biomineralization alteration. In this paper, we studied the role of pH on the growth of the pathogen and formulated hypothesis on the establishment of BRD by V. tapetis .

Methods and Results
In this study, we monitored the evolution of pH during the growth of V. tapetis in a range of pH and temperatures. We also measured the pH of Manila clam hemolymph and extrapallial fluids during infection by V. tapetis . We highlighted that V. tapetis modulates the external pH during its growth, to a value of 7.70. During the development of BRD, V. tapetis also influences extrapallial fluids and hemolymph pH in vitro in the first hours of exposure and in vivo after 3 days of infection.

Our experiments have shown a close interaction between V. tapetis CECT4600, a pathogen of Manila clam that induces BRD, and the pH of different compartments of the animals during infection. These results indicate that that the bacterium, through a direct mechanism or as a consequence of physiological changes encountered in the animal during infection, is able to interfere with the pH of Manila clam fluids. This pH modification might promote the infection process or at least create an imbalance within the animal, that would favor its persistence. This last hypothesis should be tested in future experiment.

Significance and Impact of Study
This study is the first observation of pH modifications in the context of BRD and might orient future research on the fine mechanisms of pH modulation associated to BRD.

Continue reading ‘External pH modulation during the growth of Vibrio tapetis , the etiological agent of Brown Ring Disease’

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Ocean acidification in the IPCC AR5 WG II

OUP book