Posts Tagged 'molecular biology'

Plastic responses of bryozoans to ocean acidification

Phenotypic plasticity has the potential to allow organisms to respond rapidly to global environmental change, but the range and effectiveness of these responses are poorly understood across taxa and growth strategies. Colonial organisms might be particularly resilient to environmental stressors, as organizational modularity and successive asexual generations can allow for distinctively flexible responses in the aggregate form. We performed laboratory experiments to examine the effects of increasing dissolved carbon dioxide (i.e. ocean acidification) on the colonial bryozoan Celleporella cornuta sampled from two source populations within a coastal upwelling region of the northern California coast. Bryozoan colonies were remarkably plastic under these carbon dioxide (CO2) treatments. Colonies raised under high CO2 grew more quickly, investing less in reproduction and producing lighter skeletons when compared to genetically identical clones raised under current atmospheric values. Bryozoans held in high CO2 conditions also changed the Mg/Ca ratio of skeletal calcite and increased the expression of organic coverings in new growth, which may serve as protection against acidified water. We also observed strong differences between populations in reproductive investment and organic covering reaction norms, consistent with adaptive responses to persistent spatial variation in local oceanographic conditions. Our results demonstrate that phenotypic plasticity and energetic trade-offs can mediate biological responses to global environmental change, and highlight the broad range of strategies available to colonial organisms.

Continue reading ‘Plastic responses of bryozoans to ocean acidification’

Homarus gammarus (Crustacea: Decapoda) larvae under an ocean acidification scenario: responses across different levels of biological organization

The present study evaluated the effects of exposure to different target pCO2 levels: control (C: 370μatm, pH = 8.15) and ocean acidification (OA: 710μatm, pH = 7.85) on development and biochemical responses related with oxidative stress and energy metabolism during the crustacean Homarus gammarus (L.) larval development, integrating different levels of biological organization. After hatching in the laboratory, larvae from the same female brood were exposed to the described conditions from hatching until reaching Stage III (last larval stage – 11 days). H. gammarus larvae demonstrated some susceptibility when addressing the predicted pCO2 levels for 2100. Further analysis at the biochemical and physiological level highlighted the occurrence of oxidative stress in the OA scenario (Superoxide Dismutase reduction and higher DNA damage) that was followed by developmental effects, increased inter-moult period from SII to SIII and reduced growth. The extended exposure to these conditions may affect organisms’ key life-cycle functions such as physiological resistance, growth, sexual maturation, or reproduction with implications in their future fitness and population dynamics.

Continue reading ‘Homarus gammarus (Crustacea: Decapoda) larvae under an ocean acidification scenario: responses across different levels of biological organization’

Microbiome dynamics in early life stages of the scleractinian coral Acropora gemmifera in response to elevated pCO2

Reef-building corals are complex holobionts, harbouring diverse microorganisms that play essential roles in maintaining coral health. However, microbiome development in early life stages of corals remains poorly understood. Here, microbiomes of Acropora gemmifera were analysed during spawning and early developmental stages, and also under different seawater partial pressure of CO2 (pCO2) conditions, using amplicon sequencing of 16S rRNA gene for bacteria and archaea and of ITS2 for Symbiodinium. No remarkable microbiome shift was observed in adults before and after spawning. Moreover, microbiomes in eggs were highly similar to those in spawned adults, possibly suggesting a vertical transmission from parents to offspring. However, significant stage-specific changes were found in coral microbiome during development, indicating that host development played a dominant role in shaping coral microbiome. Specifically, Cyanobacteria were particularly abundant in 6-day-old juveniles, but decreased largely in 31-day-old juveniles with a possible subclade shift in Symbiodinium dominance from C2r to D17. Larval microbiome showed changes in elevated pCO2, while juvenile microbiomes remained rather stable in response to higher pCO2. This study provides novel insights into the microbiome development during the critical life stages of coral.

Continue reading ‘Microbiome dynamics in early life stages of the scleractinian coral Acropora gemmifera in response to elevated pCO2’

Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis

Highlights

  • Exposure to futuristic concentration of pCO2 modulates innate immune response.
  • After OA-stress, gene expression is partially counteracted after pathogen challenge.
  • pCO2 might trigger specific immune-related genes at early stages of infection.
  • Combination of OA and bacterial infection seems to have partial antagonistic effects.


Abstract

Ocean acidification (OA) is one of the main consequences of increasing atmospheric carbon dioxide (CO2), impacting key biological processes of marine organisms such as development, growth and immune response. However, there are scarce studies on the influence of OA on marine invertebrates’ ability to cope with pathogens. This study evaluated the single and combined effects of OA and bacterial infection on the transcription expression of genes related to antioxidant system, antimicrobial peptides and pattern recognition receptors in the edible mussel Mytilus chilensis. Individuals of M. chilensis were exposed during 60 days at two concentrations of pCO2 (550 and 1200 μatm) representing respectively current and future scenario of OA and were then injected with the pathogenic bacterium Vibrio anguillarum. Results evidenced an immunomodulation following the OA exposure with an up-regulation of C-type Lectin and Mytilin B and a down-regulation of Myticin A and PGRP. This immunomodulation pattern is partially counteracted after challenge with V. anguillarum with a down-regulation of the C-type lectin and Mytilin B and the up-regulation of Myticin A. In turn, these results evidence that pCO2-driven OA scenarios might triggers specific immune-related genes at early stages of infection, promoting the transcription of antimicrobial peptides and patterns recognition receptors. This study provides new evidence of how the immune response of bivalves is modulated by higher CO2 conditions in the ocean, as well one factor for the resilience of marine population upon global change scenarios.

Continue reading ‘Ocean acidification and pathogen exposure modulate the immune response of the edible mussel Mytilus chilensis’

Responses of neurogenesis and neuroplasticity related genes to elevated CO2 levels in the brain of three teleost species

The continuous increase of anthropogenic CO2 in the atmosphere resulting in ocean acidification has been reported to affect brain function in some fishes. During adulthood, cell proliferation is fundamental for fish brain growth and for it to adapt in response to external stimuli, such as environmental changes. Here we report the first expression study of genes regulating neurogenesis and neuroplasticity in brains of three-spined stickleback (Gasterosteus aculeatus), cinnamon anemonefish (Amphiprion melanopus) and spiny damselfish (Acanthochromis polyacanthus) exposed to elevated CO2. The mRNA expression levels of the neurogenic differentiation factor (NeuroD) and doublecortin (DCX) were upregulated in three-spined stickleback exposed to high-CO2 compared with controls, while no changes were detected in the other species. The mRNA expression levels of the proliferating cell nuclear antigen (PCNA) and the brain-derived neurotrophic factor (BDNF) remained unaffected in the high-CO2 exposed groups compared to the control in all three species. These results indicate a species-specific regulation of genes involved in neurogenesis in response to elevated ambient CO2 levels. The higher expression of NeuroD and DCX mRNA transcripts in the brain of high-CO2–exposed three-spined stickleback, together with the lack of effects on mRNA levels in cinnamon anemonefish and spiny damselfish, indicate differences in coping mechanisms among fish in response to the predicted-future CO2 level.

Continue reading ‘Responses of neurogenesis and neuroplasticity related genes to elevated CO2 levels in the brain of three teleost species’

Genome-wide mutation rate response to pH change in the coral reef pathogen Vibrio shilonii AK1

Recent application of mutation accumulation techniques combined with whole-genome sequencing (MA/WGS) has greatly promoted studies of spontaneous mutation. However, such explorations have rarely been conducted on marine organisms, and it is unclear how marine habitats have influenced genome stability. This report resolves the mutation rate and spectrum of the coral reef pathogen Vibrio shilonii, which causes coral bleaching and endangers the biodiversity maintained by coral reefs. We found that its mutation rate and spectrum are highly similar to those of other studied bacteria from various habitats, despite the saline environment. The mutational properties of this marine bacterium are thus controlled by other general evolutionary forces such as natural selection and genetic drift. We also found that as pH drops, the mutation rate decreases and the mutation spectrum is biased in the direction of generating G/C nucleotides. This implies that evolutionary features of this organism and perhaps other marine microbes might be altered by the increasingly acidic ocean water caused by excess CO2 emission. Nonetheless, further exploration is needed as the pH range tested in this study was rather narrow and many other possible mutation determinants, such as carbonate increase, are associated with ocean acidification.

Continue reading ‘Genome-wide mutation rate response to pH change in the coral reef pathogen Vibrio shilonii AK1’

Minor impacts of reduced pH on bacterial biofilms on settlement tiles along natural pH gradients at two CO2 seeps in Papua New Guinea

Bacterial biofilms provide cues for the settlement of marine invertebrates such as coral larvae, and are therefore important for the resilience and recovery of coral reefs. This study aimed to better understand how ocean acidification may affect the community composition and diversity of bacterial biofilms on surfaces under naturally reduced pH conditions. Settlement tiles were deployed at coral reefs in Papua New Guinea along pH gradients created by two CO2 seeps. Biofilms on upper and lower tiles surfaces were sampled 5 and 13 months after deployment. Automated Ribosomal Intergenic Spacer Analysis was used to characterize 240 separate bacterial communities, complemented by amplicon sequencing of the bacterial 16S rRNA gene of 16 samples. Bacterial biofilms consisted predominantly of Alpha-, Gamma-, and Delta-proteobacteria, as well as Cyanobacteria, Flavobacteriia, and Cytophagia, whereas taxa that induce settlement of invertebrate larvae only accounted for a small fraction of the community. Bacterial biofilm composition was heterogeneous, with on average only ∼25% of operational taxonomic units shared between samples. Among the observed environmental parameters, pH was only weakly related to community composition (R2 ∼ 1%), and was unrelated to community richness and evenness. In contrast, biofilms strongly differed between upper and lower tile surfaces (contrasting in light exposure and grazing intensity). There also appeared to be a strong interaction between bacterial biofilm composition and the macroscopic components of the tile community. Our results suggest that on mature settlement surfaces in situ, pH does not have a strong impact on the composition of bacterial biofilms. Other abiotic and biotic factors such as light exposure and interactions with other organisms may be more important in shaping bacterial biofilms on mature surfaces than changes in seawater pH.

Continue reading ‘Minor impacts of reduced pH on bacterial biofilms on settlement tiles along natural pH gradients at two CO2 seeps in Papua New Guinea’


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