Posts Tagged 'physiology'



Uncovering mechanisms of global ocean change effects on the Dungeness crab (Cancer magister) through metabolomics analysis

The Dungeness crab is an economically and ecologically important species distributed along the North American Pacific coast. To predict how Dungeness crab may physiologically respond to future global ocean change on a molecular level, we performed untargeted metabolomic approaches on individual Dungeness crab juveniles reared in treatments that mimicked current and projected future pH and dissolved oxygen conditions. We found 94 metabolites and 127 lipids responded in a condition-specific manner, with a greater number of known compounds more strongly responding to low oxygen than low pH exposure. Pathway analysis of these compounds revealed that juveniles may respond to low oxygen through evolutionarily conserved processes including downregulating glutathione biosynthesis and upregulating glycogen storage, and may respond to low pH by increasing ATP production. Most interestingly, we found that the response of juveniles to combined low pH and low oxygen exposure was most similar to the low oxygen exposure response, indicating low oxygen may drive the physiology of juvenile crabs more than pH. Our study elucidates metabolic dynamics that expand our overall understanding of how the species might respond to future ocean conditions and provides a comprehensive dataset that could be used in future ocean acidification response studies.

Continue reading ‘Uncovering mechanisms of global ocean change effects on the Dungeness crab (Cancer magister) through metabolomics analysis’

De novo transcriptome assembly and gene expression profile of thermally challenged green abalone (Haliotis fulgens: Gastropoda) under acute hypoxia and hypercapnia

Highlights

• Abalone gene expression under warming, hypoxia, and hypercapnia, individually and combined.

• The response reflects enhanced damage control at the expense of energy metabolism.

• Gene networks of gill and muscle conform with different levels of thermal sensitivity.

• Warming combined with hypercapnia and hypoxia enhanced mitochondrial capacity.

Abstract

Transcriptional regulation constitutes a rapid response of marine organisms facing stressful environmental conditions, such as the concomitant exposure to warming, ocean acidification and hypoxia under climate change. In previous studies, we investigated whole-organism physiological patterns and cellular metabolism in gill and muscle of the marine gastropod Haliotis fulgens in response to increasing temperature (18 °C to 32 °C at +3 °C per day) under hypoxia (50% air saturation), hypercapnia (1000 μatm pCO2) and both factors combined. Here, we report investigations of the molecular responses of H. fulgens to temperature and identify mechanisms concomitantly affected by hypoxia and hypercapnia. A de novo transcriptome assembly with subsequent quantitative PCR and correlation network analysis of genes involved in the molecular response were used to unravel the correlations between gene expression patterns under the different experimental conditions. The correlation networks identified a shift from the expression of genes involved in energy metabolism (down-regulated) to the up-regulation of Hsp70 during warming under all experimental conditions in gill and muscle, indicating a strong up-regulation of damage prevention and repair systems at sustained cellular energy production. However, a higher capacity for anaerobic succinate production was evicted in gill, matching with observations from our previous studies indicating succinate accumulation in gill but not in muscle. Additionally, warming under hypoxia and hypercapnia kept mRNA levels of citrate synthase in both tissues unchanged following a similar pattern as muscle enzyme capacity from a previous study, suggesting an emphasis on maintaining rather than down-regulating mitochondrial activity.

Continue reading ‘De novo transcriptome assembly and gene expression profile of thermally challenged green abalone (Haliotis fulgens: Gastropoda) under acute hypoxia and hypercapnia’

Provision of carbon skeleton for lipid synthesis from the breakdown of intracellular protein and soluble sugar in Phaeodactylum tricornutum under high CO2

Background
Increasing CO2 emissions have resulted in ocean acidification, affecting marine plant photosynthesis and changing the nutrient composition of marine ecosystems. The physiological and biochemical processes of marine phytoplankton in response to ocean acidification have been reported, but have been mainly focused on growth and photosynthetic physiology. To acquire a thorough knowledge of the molecular regulation mechanisms, model species with clear genetic background should be selected for systematic study. Phaeodactylum tricornutum is a pennate diatom with the characteristics of small genome size, short generation cycle, and easy to transform. Furthermore, the genome of P. tricornutum has been completely sequenced.

Results and discussion
In this study, P. tricornutum was cultured at high and normal CO2 concentrations. Cell composition changes during culture time were investigated. The 13C isotope tracing technique was used to determine fractional labeling enrichments for the main cellular components. The results suggested that when lipid content increased significantly under high CO2 conditions, total protein and soluble sugar contents decreased. The 13C labeling experiment indicated that the C skeleton needed for fatty acid C chain elongation in lipid synthesis under high CO2 conditions is not mainly derived from NaHCO3 (carbon fixed by photosynthesis).

Conclusion
This study indicated that breakdown of intracellular protein and soluble sugar provide C skeleton for lipid synthesis under high CO2 concentration.

Continue reading ‘Provision of carbon skeleton for lipid synthesis from the breakdown of intracellular protein and soluble sugar in Phaeodactylum tricornutum under high CO2’

Combined effects of acute temperature change and elevated pCO2 on the metabolic rates and hypoxia tolerances of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata)

Understanding how rising temperatures, ocean acidification, and hypoxia affect the performance of coastal fishes is essential to predicting species-specific responses to climate change. Although a population’s habitat influences physiological performance, little work has explicitly examined the multi-stressor responses of species from habitats differing in natural variability. Here, clearnose skate (Rostaraja eglanteria) and summer flounder (Paralichthys dentatus) from mid-Atlantic estuaries, and thorny skate (Amblyraja radiata) from the Gulf of Maine, were acutely exposed to current and projected temperatures (20, 24, or 28 °C; 22 or 30 °C; and 9, 13, or 15 °C, respectively) and acidification conditions (pH 7.8 or 7.4). We tested metabolic rates and hypoxia tolerance using intermittent-flow respirometry. All three species exhibited increases in standard metabolic rate under an 8 °C temperature increase (Q10 of 1.71, 1.07, and 2.56, respectively), although this was most pronounced in the thorny skate. At the lowest test temperature and under the low pH treatment, all three species exhibited significant increases in standard metabolic rate (44–105%; p < 0.05) and decreases in hypoxia tolerance (60–84% increases in critical oxygen pressure; p < 0.05). This study demonstrates the interactive effects of increasing temperature and changing ocean carbonate chemistry are species-specific, the implications of which should be considered within the context of habitat.

Continue reading ‘Combined effects of acute temperature change and elevated pCO2 on the metabolic rates and hypoxia tolerances of clearnose skate (Rostaraja eglanteria), summer flounder (Paralichthys dentatus), and thorny skate (Amblyraja radiata)’

Decreasing carbonate load of seagrass leaves with increasing latitude

Highlights

• Seagrass epiphyte carbonate load was examined along a latitudinal and Ω gradient.

• Epiphyte carbonate content, load and production decreased as latitude increased.

• Epiphyte carbonate content, load and production increased as Ω increased.

• These trends are similar to those described in other carbonate producer communities.

Abstract

Seagrass meadows play a significant role in the formation of carbonate sediments, serving as a substrate for carbonate-producing epiphyte communities. The magnitude of the epiphyte load depends on plant structural and physiological parameters, related to the time available for epiphyte colonization. Yet, the carbonate accumulation is likely to also depend on the carbonate saturation state of seawater (Ω) that tends to decrease as latitude increases due to decreasing temperature and salinity. A decrease in carbonate accumulation with increasing latitude has already been demonstrated for other carbonate producing communities. The aim of this study was to assess whether there was any correlation between latitude and the epiphyte carbonate load and net carbonate production rate on seagrass leaves. Shoots from 8 different meadows of the Zostera genus distributed across a broad latitudinal range (27 °S to up to 64 °N) were sampled along with measurements of temperature and Ω. The Ω within meadows significantly decreased as latitude increased and temperature decreased. The mean carbonate content and load on seagrass leaves ranged from 17 % DW to 36 % DW and 0.4-2.3 mg CO3 cm-2, respectively, and the associated mean carbonate net production rate varied from 0.007 to 0.9 mg CO3 cm-2 d-1. Mean carbonate load and net production rates decreased from subtropical and tropical, warmer regions towards subpolar latitudes, consistent with the decrease in Ω. These results point to a latitudinal variation in the contribution of seagrass to the accumulation of carbonates in their sediments which affect important processes occurring in seagrass meadows, such as nutrient cycling, carbon sequestration and sediment accretion.

Continue reading ‘Decreasing carbonate load of seagrass leaves with increasing latitude’

High pCO2 promotes coral primary production

While research on ocean acidification (OA) impacts on coral reefs has focused on calcification, relatively little is known about effects on coral photosynthesis and respiration, despite these being among the most plastic metabolic processes corals may use to acclimatize to adverse conditions. Here, we present data collected between 2016 and 2018 at three natural CO2 seeps in Papua New Guinea where we measured the metabolic flexibility (i.e. in hospite photosynthesis and dark respiration) of 12 coral species. Despite some species-specific variability, metabolic rates as measured by net oxygen flux tended to be higher at high pCO2 (ca 1200 µatm), with increases in photosynthesis exceeding those of respiration, suggesting greater productivity of Symbiodiniaceae photosynthesis in hospite, and indicating the potential for metabolic flexibility that may enable these species to thrive in environments with high pCO2. However, laboratory and field observations of coral mortality under high CO2 conditions associated with coral bleaching suggests that this metabolic subsidy does not result in coral higher resistance to extreme thermal stress. Therefore, the combined effects of OA and global warming may lead to a strong decrease in coral diversity despite the stimulating effect on coral productivity of OA alone.

Continue reading ‘High pCO2 promotes coral primary production’

Effects of ocean acidification and short-term light/temperature stress on biogenic dimethylated sulfur compounds cycling in the Changjiang River Estuary

Ocean acidification (OA) affects marine primary productivity and community structure. Therefore, OA may influence the biogeochemical cycles of volatile biogenic dimethyl sulfide (DMS), and its precursor dimethylsulfoniopropionate (DMSP) and photochemical oxidation product dimethyl sulfoxide (DMSO). A 23-day shipboard incubation experiment investigated the short-term response of the production and cycling of biogenic sulfur compounds to OA in the Changjiang River Estuary to understand the effects of OA on biogenic sulfur compounds. Phytoplankton abundance and community composition showed a marked difference at three different pH levels at the late stage of the experiment. Significant reductions in chlorophyll a (Chl-a), DMS, particulate DMSP (DMSPp) and dissolved DMSO (DMSOd) concentrations were identified under high CO2 levels. Moreover, minimal changes were observed in the productions of dissolved DMSP (DMSPd) and particulate DMSO (DMSOp) among the treatments. The ratios of DMS, total DMSP (DMSPt) and total DMSO (DMSOt) to Chl-a were not affected by a change in pH. Furthermore, the concentrations of DMS and DMSOd were closely related to the mean bacterial abundance at the three pH levels. Additional short-term (8 h) incubation experiments on the light and temperature effects showed that the influence of pH on the production of dimethylated sulfur compounds also depended on solar radiation and temperature. Under natural and UVB light, DMS photodegradation rates increased by 1.6 to 4.2 times at low pH levels. Thus, OA may lead to decreasing DMS concentrations in surface seawater. Light and temperature conditions also play important roles in the production and cycling of biogenic sulfur compounds.

Continue reading ‘Effects of ocean acidification and short-term light/temperature stress on biogenic dimethylated sulfur compounds cycling in the Changjiang River Estuary’


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Ocean acidification in the IPCC AR5 WG II

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