Posts Tagged 'physiology'

Understanding feedbacks between ocean acidification and coral reef metabolism

Biogeochemical feedbacks from benthic metabolism have been hypothesized as a potential mechanism to buffer some effects of ocean acidification on coral reefs. The article in JGR-Oceans by DeCarlo et al. demonstrates the importance of benthic community health on this feedback from Dongsha Atoll in the South China Sea.

Continue reading ‘Understanding feedbacks between ocean acidification and coral reef metabolism’

Future climate change scenarios differentially affect three abundant algal species in southwestern Australia

Three species of macroalgae (Ecklonia radiata, Sargassum linearifolium, and Laurencia brongniartii) were subjected to future climate change conditions, tested directly for changes in their physiology and chemical ecology, and used in feeding assays with local herbivores to identify the indirect effects of climatic stressors on subsequent levels of herbivory. Each alga had distinct physical and chemical responses to the changes in environmental conditions. In high temperature conditions, S. linearifolium exhibited high levels of bleaching and low maximum quantum yield. For E. radiata, the alga became more palatable to herbivores and the C:N ratios were either higher or lower, dependent on the treatment. Laurencia brongniartii was effected in all manipulations when compared to controls, with increases in bleaching, blade density, and C:N ratios and decreases in growth, maximum quantum yield, blade toughness, total phenolics and consumption by mesograzers. The differential responses we observed in each species have important implications for benthic communities in projected climate change conditions and we suggest that future studies target multi-species assemblage responses.

Continue reading ‘Future climate change scenarios differentially affect three abundant algal species in southwestern Australia’

The uronic acid content of coccolith-associated polysaccharides provides insight into coccolithogenesis and past climate

Unicellular phytoplanktonic algae (coccolithophores) are among the most prolific producers of calcium carbonate on the planet, with a production of ∼1026 coccoliths per year. During their lith formation, coccolithophores mainly employ coccolith-associated polysaccharides (CAPs) for the regulation of crystal nucleation and growth. These macromolecules interact with the intracellular calcifying compartment (coccolith vesicle) through the charged carboxyl groups of their uronic acid residues. Here we report the isolation of CAPs from modern day coccolithophores and their prehistoric predecessors and we demonstrate that their uronic acid content (UAC) offers a species-specific signature. We also show that there is a correlation between the UAC of CAPs and the internal saturation state of the coccolith vesicle that, for most geologically abundant species, is inextricably linked to carbon availability. These findings suggest that the UAC of CAPs reports on the adaptation of coccolithogenesis to environmental changes and can be used for the estimation of past CO2 concentrations.

Continue reading ‘The uronic acid content of coccolith-associated polysaccharides provides insight into coccolithogenesis and past climate’

Integrated regulatory and metabolic networks of the marine diatom Phaeodactylum tricornutum predict the response to rising CO2 levels

Diatoms are eukaryotic microalgae that are responsible for up to 40% of the ocean’s primary productivity. How diatoms respond to environmental perturbations such as elevated carbon concentrations in the atmosphere is currently poorly understood. We developed a transcriptional regulatory network based on various transcriptome sequencing expression libraries for different environmental responses to gain insight into the marine diatom’s metabolic and regulatory interactions and provide a comprehensive framework of responses to increasing atmospheric carbon levels. This transcriptional regulatory network was integrated with a recently published genome-scale metabolic model of Phaeodactylum tricornutum to explore the connectivity of the regulatory network and shared metabolites. The integrated regulatory and metabolic model revealed highly connected modules within carbon and nitrogen metabolism. P. tricornutum’s response to rising carbon levels was analyzed by using the recent genome-scale metabolic model with cross comparison to experimental manipulations of carbon dioxide.

IMPORTANCE: Using a systems biology approach, we studied the response of the marine diatom Phaeodactylum tricornutum to changing atmospheric carbon concentrations on an ocean-wide scale. By integrating an available genome-scale metabolic model and a newly developed transcriptional regulatory network inferred from transcriptome sequencing expression data, we demonstrate that carbon metabolism and nitrogen metabolism are strongly connected and the genes involved are coregulated in this model diatom. These tight regulatory constraints could play a major role during the adaptation of P. tricornutum to increasing carbon levels. The transcriptional regulatory network developed can be further used to study the effects of different environmental perturbations on P. tricornutum’s metabolism.

Continue reading ‘Integrated regulatory and metabolic networks of the marine diatom Phaeodactylum tricornutum predict the response to rising CO2 levels’

Ocean acidification modulates expression of genes and physiological performance of a marine diatom

Ocean Acidification (OA) is known to affect various aspects of physiological performances of diatoms, but little is known about the underlining molecular mechanisms involved. Here, we show that in the model diatom Phaeodactylum tricornutum, the expression of key genes associated with photosynthetic light harvesting as well as those encoding Rubisco, carbonic anhydrase, NADH dehydrogenase and nitrite reductase, are modulated by OA (1000 μatm, pHnbs 7.83). Growth and photosynthetic carbon fixation were enhanced by elevated CO2. OA treatment decreased the expression of β-carbonic anhydrase (β-ca), which functions in balancing intracellular carbonate chemistry and the CO2 concentrating mechanism (CCM). The expression of the genes encoding fucoxanthin chlorophyll a/c protein (lhcf type (fcp)), mitochondrial ATP synthase (mtATP), ribulose-1, 5-bisphosphate carboxylase/oxygenase large subunit gene (rbcl) and NADH dehydrogenase subunit 2 (ndh2), were down-regulated during the first four days (< 8 generations) after the cells were transferred from LC (cells grown under ambient air condition; 390 μatm; pHnbs 8.19) to OA conditions, with no significant difference between LC and HC treatments with the time elapsed. The expression of nitrite reductase (nir) was up-regulated by the OA treatment. Additionally, the genes for these proteins (NiR, FCP, mtATP synthase, β-CA) showed diel expression patterns. It appeared that the enhanced photosynthetic and growth rates under OA could be attributed to stimulated nitrogen assimilation, increased CO2 availability or saved energy from down-regulation of the CCM and consequently lowered cost of protein synthesis versus that of non-nitrogenous cell components.

Continue reading ‘Ocean acidification modulates expression of genes and physiological performance of a marine diatom’

Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg

In marine invertebrates, the environmental history of the mother can influence fecundity and egg size. Acclimation of females in climate change stressors, increased temperature and low pH, results in a decrease in egg number and size in many taxa, with the exception of cephalopods, where eggs increase in size. With respect to spawned eggs, near future levels of ocean acidification can interfere with the eggs’ block to polyspermy and intracellular pH. Reduction of the extracellular egg jelly coat seen in low pH conditions has implications for impaired egg function and fertilization. Some fast generation species (e.g. copepods, polychaetes) have shown restoration of female reproductive output after several generations in treatments. It will be important to determine if the changes to egg number and size induced by exposure to climate change stressors are heritable.

Continue reading ‘Marine gametes in a changing ocean: Impacts of climate change stressors on fecundity and the egg’

Intertidal pool fish Girella laevifrons (Kyphosidae) shown strong physiological homeostasis but shy personality: The cost of living in hypercapnic habitats

Tide pools habitats are naturally exposed to a high degree of environmental variability. The consequences of living in these extreme habitats are not well established. In particular, little it is known about of the effects of hypercanic seawater (i.e. high pCO2 levels) on marine vertebrates such as intertidal pool fish. The aim of this study was to evaluate the effects of increased pCO2 on the physiology and behavior in juveniles of the intertidal pool fish Girella laevifrons. Two nominal pCO2 concentrations (400 and 1600 μatm) were used. We found that exposure to hypercapnic conditions did not affect oxygen consumption and absorption efficiency. However, the lateralization and boldness behavior was significantly disrupted in high pCO2 conditions. In general, a predator-risk cost of boldness is assumed, thus the increased occurrence of shy personality in juvenile fishes may result in a change in the balance of this biological interaction, with significant ecological consequences.

Continue reading ‘Intertidal pool fish Girella laevifrons (Kyphosidae) shown strong physiological homeostasis but shy personality: The cost of living in hypercapnic habitats’


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Ocean acidification in the IPCC AR5 WG II

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