The plasticity of some coral-associated microbial communities under stressors like warming and ocean acidification suggests the microbiome has a role in the acclimatization of corals to future ocean conditions. Here, we evaluated the acclimatization potential of coral-associated microbial communities of four Hawaiian coral species (Porites compressa, Porites lobata, Montipora capitata, and Pocillopora acuta) over 22-month mesocosm experiment. The corals were exposed to one of four treatments: control, ocean acidification, ocean warming, or combined future ocean conditions. Over the 22-month study, 33–67% of corals died or experienced a loss of most live tissue coverage in the ocean warming and future ocean treatments while only 0–10% died in the ocean acidification and control. Among the survivors, coral-associated microbial communities responded to the chronic future ocean treatment in one of two ways: (1) microbial communities differed between the control and future ocean treatment, suggesting the potential capacity for acclimatization, or (2) microbial communities did not significantly differ between the control and future ocean treatment. The first strategy was observed in both Porites species and was associated with higher survivorship compared to M. capitata and P. acuta which exhibited the second strategy. Interestingly, the microbial community responses to chronic stressors were independent of coral physiology. These findings indicate acclimatization of microbial communities may confer resilience in some species of corals to chronic warming associated with climate change. However, M. capitata genets that survived the future ocean treatment hosted significantly different microbial communities from those that died, suggesting the microbial communities of the survivors conferred some resilience. Thus, even among coral species with inflexible microbial communities, some individuals may already be tolerant to future ocean conditions. These findings suggest that coral-associated microbial communities could play an important role in the persistence of some corals and underlie climate change-driven shifts in coral community composition.
Continue reading ‘Long-term coral microbial community acclimatization is associated with coral survival in a changing climate’Posts Tagged 'prokaryotes'
Long-term coral microbial community acclimatization is associated with coral survival in a changing climate
Published 4 October 2023 Science ClosedTags: abundance, adaptation, biological response, BRcommunity, community composition, corals, laboratory, mesocosms, mortality, North Pacific, otherprocess, prokaryotes
Fermentative iron reduction buffers acidification and promotes microbial metabolism in marine sediments
Published 19 September 2023 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, laboratory, mitigation, North Pacific, otherprocess, physiology, prokaryotes, sediment
Microbial iron reduction is a crucial process in natural ecosystems, contributing to the cycling of elements and supporting the biological activities of organisms. However, the significance of fermentative iron reduction in marine environments and microbial metabolism remains understudied compared with iron reduction coupled with respiration. The main objective of our study was to investigate the influence of fermentative iron reduction on microbial populations and marine sediment. Our findings revealed a robust iron-reducing activity in the enriched marine sediment, demonstrating a maximum ferrihydrite-reducing rate of 0.063 mmol/h. Remarkably, ferrihydrite reduction exhibited an intriguing pH-buffering effect through the release of OH+ and Fe2+ ions, distinct from fermentation alone. This effect resulted in substantial improvements in glucose consumption (71.4%), bacterial growth (48.1%), and metabolite production (80.8%). To further validate the acidification-buffering and metabolism-promoting effects of ferrihydrite reduction, we conducted iron-reducing experiments using a pure strain, Clostridium pasteurianum DMS525. The observed pH-buffering effect resulted from microbial iron reduction in marine sediment and has potential environmental implications by reducing CO2 emissions, mitigating acidification, and preserving the delicate balance of marine ecosystems.
Continue reading ‘Fermentative iron reduction buffers acidification and promotes microbial metabolism in marine sediments’Microbial communities inhabiting shallow hydrothermal vents as sentinels of acidification processes
Published 4 September 2023 Science ClosedTags: abundance, archaea, biological response, BRcommunity, community composition, field, Mediterranean, molecular biology, otherprocess, prokaryotes, sediment, vents
Introduction: Shallow hydrothermal vents are considered natural laboratories to study the effects of acidification on biota, due to the consistent CO2 emissions with a consequent decrease in the local pH.
Methods: Here the microbial communities of water and sediment samples from Levante Bay (Vulcano Island) with different pH and redox conditions were explored by Next Generation Sequencing techniques. The taxonomic structure was elucidated and compared with previous studies from the same area in the last decades.
Results and discussion: The results revealed substantial shifts in the taxonomic structure of both bacterial and archaeal communities, with special relevance in the sediment samples, where the effects of external parameters probably act for a long time. The study demonstrates that microbial communities could be used as indicators of acidification processes, by shaping the entire biogeochemical balance of the ecosystem in response to stress factors. The study contributes to understanding how much these communities can tell us about future changes in marine ecosystems.
Continue reading ‘Microbial communities inhabiting shallow hydrothermal vents as sentinels of acidification processes’Genomic signatures suggesting adaptation to ocean acidification in a coral holobiont from volcanic CO2 seeps
Published 25 July 2023 Science ClosedTags: adaptation, biological response, BRcommunity, corals, field, molecular biology, otherprocess, physiology, phytoplankton, prokaryotes, South Pacific, vents
Ocean acidification, caused by anthropogenic CO2 emissions, is predicted to have major consequences for reef-building corals, jeopardizing the scaffolding of the most biodiverse marine habitats. However, whether corals can adapt to ocean acidification and how remains unclear. We addressed these questions by re-examining transcriptome and genome data of Acropora millepora coral holobionts from volcanic CO2 seeps with end-of-century pH levels. We show that adaptation to ocean acidification is a wholistic process involving the three main compartments of the coral holobiont. We identified 441 coral host candidate adaptive genes involved in calcification, response to acidification, and symbiosis; population genetic differentiation in dinoflagellate photosymbionts; and consistent transcriptional microbiome activity despite microbial community shifts. Coral holobionts from natural analogues to future ocean conditions harbor beneficial genetic variants with far-reaching rapid adaptation potential. In the face of climate change, these populations require immediate conservation strategies as they could become key to coral reef survival.
Continue reading ‘Genomic signatures suggesting adaptation to ocean acidification in a coral holobiont from volcanic CO2 seeps’Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification
Published 21 July 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, phanerogams, photosynthesis, physiology, prokaryotes, temperature
Seagrass meadows play vital ecological roles in the marine ecosystem. Global climate change poses considerable threats to seagrass survival. However, it is unclear how seagrass and its associated bacteria will respond under future complex climate change scenarios. This study explored the effects of ocean warming (+2 °C) and ocean acidification (−0.4 units) on seagrass physiological indexes and bacterial communities (sediment and rhizosphere bacteria) of the seagrass Thalassia hemprichii during an experimental exposure of 30 days. Results demonstrated that the synergistic effect of ocean warming and ocean acidification differed from that of one single factor on seagrass and the associated bacterial community. The seagrass showed a weak resistance to ocean warming and ocean acidification, which manifested through the increase in the activity of typical oxidoreductase enzymes. Moreover, the synergistic effect of ocean warming and ocean acidification caused a significant decrease in seagrass’s chlorophyll content. Although the bacterial community diversity exhibited higher resistance to ocean warming and ocean acidification, further bacterial functional analysis revealed the synergistic effect of ocean warming and ocean acidification led to significant increases in SOX-related genes abundance which potentially supported the seagrass in resisting climate stress by producing sulfates and oxidizing hydrogen sulfide. More stable bacterial communities were detected in the seagrass rhizosphere under combined ocean warming and ocean acidification. While for one single environmental stress, simpler networks were detected in the rhizosphere. In addition, the observed significant correlations between several modules of the bacterial community and the physiological indexes of the seagrass indicate the possible intimate interaction between seagrass and bacteria under ocean warming and ocean acidification. This study extends our understanding regarding the role of seagrass associated bacterial communities and sheds light on both the prediction and preservation of the seagrass meadow ecosystems in response to global climate change.
Continue reading ‘Seagrass Thalassia hemprichii and associated bacteria co-response to the synergistic stress of ocean warming and ocean acidification’Acclimation to various temperature and pCO2 levels does not impact the competitive ability of two strains of Skeletonema marinoi in natural communities subjected to different pCO2 treatments
Published 12 July 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, otherprocess, phytoplankton, prokaryotes, temperature
Understanding the long-term response of key marine phytoplankton species to ongoing global changes is pivotal in determining how oceanic community composition will respond over the coming decades. To better understand the impact of ocean acidification and warming, we acclimated two strains of Skeletonema marinoi isolated from natural communities to three pCO2 (400 atm, 600 atm and 1000 atm) for 8 months and five temperature conditions (7°C, 10°C, 13°C, 16°C and 19°C) for 11 months. These strains were then tested in natural microbial communities, exposed to three pCO2 treatments (400 atm, 600 atm and 1000 atm). DNA metabarcoding of the 16S and 18S gene for prokaryotes and eukaryotes respectively was used to show differences in abundance and diversity between the three CO2 treatments. We found there were no significant differences in acclimated S. marinoi concentrations between the three pCO2 treatments, most likely due to the high variability these strains experience in their natural environment. There were significant compositional differences between the pCO2 treatments for prokaryotes suggesting that indirect changes to phytoplankton-bacteria interactions could be a possible driver of bacterial community composition. Yet, there were no differences for eukaryotic community composition, with all treatments dominated by diatoms (but not the acclimated S. marinoi) resulting in similar biodiversity. Furthermore, strain-specific differences in community composition suggests interactions between prokaryotic and eukaryotic taxa could play a role in determining future community composition.
Continue reading ‘Acclimation to various temperature and pCO2 levels does not impact the competitive ability of two strains of Skeletonema marinoi in natural communities subjected to different pCO2 treatments’Ocean acidification altered microbial functional potential in the Arctic Ocean
Published 30 June 2023 Science ClosedTags: abundance, Arctic, biological response, BRcommunity, community composition, field, mesocosms, molecular biology, otherprocess, physiology, prokaryotes
Ocean acidification (OA) has considerably changed the metabolism and structure of plankton communities in the ocean. Evaluation of the response of the marine bacterioplankton community to OA is critical for understanding the future direction of bacterioplankton-mediated biogeochemical processes in the ocean. Understanding the diversity of functional genes is important for linking the microbial community to ecological and biogeochemical processes. However, the influence of OA on the functional diversity of bacterioplankton remains unclear. Using high-throughput functional gene microarray technology (GeoChip 4), we investigated the functional gene structure and diversity of bacterioplankton under three different pCO2 levels (control: 175 μatm, medium: 675 μatm, and high: 1085 μatm) in a large Arctic Ocean mesocosm experiment. We observed a higher evenness of microbial functional genes under elevated pCO2 compared with under low pCO2. OA induced a more stable community as evaluated by decreased dissimilarity of functional gene structure with increased pCO2. Molecular ecological networks under elevated pCO2 became more complex and stable, supporting the central ecological tenet that complexity begets stability. In particular, increased average abundances were found under elevated pCO2 for many genes involved in key metabolic processes, including carbon degradation, methane oxidization, nitrogen fixation, dissimilatory nitrite/nitrate reduction, and sulfide reduction processes. Altogether, these results indicate a significant influence of OA on the metabolism potential of bacterioplankton in the Arctic Ocean. Consequently, our study suggests that biogeochemical cycling mediated by these microbes may be altered by the OA in the future.
Continue reading ‘Ocean acidification altered microbial functional potential in the Arctic Ocean’Microbial dynamics in shallow CO2 seeps system off Panarea Island (Italy)
Published 30 June 2023 Science ClosedTags: abundance, biological response, BRcommunity, community composition, field, Mediterranean, otherprocess, physiology, prokaryotes, vents
Shallow-water hydrothermal vents are extreme environments characterized by high temperatures, low pH, and high CO2 concentrations; therefore, they are considered as suitable laboratories for studying the effect of global changes on marine microbes. We hypothesized a direct effect of vents on prokaryotic community structure and functioning in the Panarea Island’s hydrothermal system. Sampling was conducted along a 9-station transect characterized by three active emission points. The water column was stratified with a thermocline at 25 m depth and a deep chlorophyll maximum between 50 and 100 m. Prokaryotic abundance ranged from 0.2 to 1.5 × 109 cells L−1, prokaryotic carbon production from 2.4 to 75.4 ng C L−1 h−1, and exoenzymatic activities degrading proteins, phosphorylated compounds, and polysaccharides were on the order of 4–28, 2–31 and 0.2–4.16 nM h−1, respectively. While microbial abundance and production were shaped by the water column’s physical structure, alkaline phosphatase and beta-glucosidase activities seemed to be enhanced by hydrothermal fluids. The 16S rRNA gene amplicon sequencing analysis identified a surface, a deep, and a vent-influenced microbial community. In terms of relative abundance members of the SAR11 group dominated the water column, alongside Synechococcus and Prochlorococcus in surface and bottom samples, respectively. Vent-influenced stations were characterized by the presence of Thiomicrorhabdus, a sulfur-oxidizer chemolithoautotroph. Overall, this study provides insights on the coupling between microbial community structure and the biogeochemical cycling of nutrients in low-pH conditions (CO2 and H2S-based), thus addressing some of the opened questions about the response of microbes to acidification.
Continue reading ‘Microbial dynamics in shallow CO2 seeps system off Panarea Island (Italy)’Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis
Published 16 June 2023 Science ClosedTags: abundance, archaea, biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, otherprocess, physiology, porifera, prokaryotes, South Pacific, temperature
Oceans are rapidly warming and acidifying in the context of climate change, threatening sensitive marine biota including coral reef sponges. Ocean warming (OW) and ocean acidification (OA) can impact host health and associated microbiome, but few studies have investigated these effects, which are generally studied in isolation, on a specific component of the holobiont. Here we present a comprehensive view of the consequences of simultaneous OW and OA for the tropical sponge Stylissa flabelliformis. We found no interactive effect on the host health or microbiome. Furthermore, OA (pH 7.6 versus pH 8.0) had no impact, while OW (31.5 °C versus 28.5 °C) caused tissue necrosis, as well as dysbiosis and shifts in microbial functions in healthy tissue of necrotic sponges. Major taxonomic shifts included a complete loss of archaea, reduced proportions of Gammaproteobacteria and elevated relative abundances of Alphaproteobacteria. OW weakened sponge-microbe interactions, with a reduced capacity for nutrient exchange and phagocytosis evasion, indicating lower representations of stable symbionts. The potential for microbially-driven nitrogen and sulphur cycling was reduced, as was amino acid metabolism. Crucially, the dysbiosis annihilated the potential for ammonia detoxification, possibly leading to accumulation of toxic ammonia, nutrient imbalance, and host tissue necrosis. Putative defence against reactive oxygen species was greater at 31.5 °C, perhaps as microorganisms capable of resisting temperature-driven oxidative stress were favoured. We conclude that healthy symbiosis in S. flabelliformis is unlikely to be disrupted by future OA but will be deeply impacted by temperatures predicted for 2100 under a “business-as-usual” carbon emission scenario.
Continue reading ‘Future ocean conditions induce necrosis, microbial dysbiosis and nutrient cycling imbalance in the reef sponge Stylissa flabelliformis’The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts
Published 14 June 2023 Science ClosedTags: biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, physiology, primary production, prokaryotes, temperature
Reef-building corals, the foundation of tropical coral reefs, are vulnerable to climate change e.g. ocean acidification and elevated seawater temperature. Coral microbiome plays a key role in host acclimatization and maintenance of the coral holobiont’s homeostasis under different environmental conditions, however, the response patterns of coral prokaryotic symbionts to ocean acidification and/or warming are rarely known at the metatranscriptional level, particularly the knowledge of interactive and persistent effects is limited. Using branching Acropora valida and massive Galaxea fascicularis as models in a lab system simulating extreme ocean acidification (pH 7.7) and/or warming (32 °C) in the future, we investigated the changes of in situ active prokaryotic symbionts community and gene expression of corals under/after (6/9 d) acidification (A), warming (H) and acidification–warming (AH) by metatranscriptome analysis with pH8.1, 26 °C as the control.
Continue reading ‘The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts’Microbial mats as model to decipher climate change effect on microbial communities through a mesocosm study
Published 7 June 2023 Science ClosedTags: adaptation, biological response, BRcommunity, community composition, laboratory, mesocosms, methods, multiple factors, otherprocess, performance, physiology, prokaryotes, temperature
Marine environments are expected to be one of the most affected ecosystems by climate change, notably with increasing ocean temperature and ocean acidification. In marine environments, microbial communities provide important ecosystem services ensuring biogeochemical cycles. They are threatened by the modification of environmental parameters induced by climate change that, in turn, affect their activities. Microbial mats, ensuring important ecosystem services in coastal areas, are well-organized communities of diverse microorganisms representing accurate microbial models. It is hypothesized that their microbial diversity and metabolic versatility will reveal various adaptation strategies in response to climate change. Thus, understanding how climate change affects microbial mats will provide valuable information on microbial behaviour and functioning in changed environment. Experimental ecology, based on mesocosm approaches, provides the opportunity to control physical-chemical parameters, as close as possible to those observed in the environment. The exposure of microbial mats to physical-chemical conditions mimicking the climate change predictions will help to decipher the modification of the microbial community structure and function in response to it. Here, we present how to expose microbial mats, following a mesocosm approach, to study the impact of climate change on microbial community.
Continue reading ‘Microbial mats as model to decipher climate change effect on microbial communities through a mesocosm study’Strong variation in sedimental antibiotic resistomes among urban rivers, estuaries and coastal oceans: evidence from a river-connected coastal water ecosystem in northern China
Published 6 June 2023 Science ClosedTags: abundance, biological response, chemistry, field, molecular biology, North Pacific, otherprocess, prokaryotes, sediment
Sediment is thought to be a vital reservoir to spread antibiotic resistance genes (ARGs) among various natural environments. However, the spatial distribution patterns of the sedimental antibiotic resistomes around the Bohai Bay region, a river-connected coastal water ecosystem, are still poorly understood. The present study conducted a comprehensive investigation of ARGs among urban rivers (UR), estuaries (ES) and Bohai Bay (BHB) by metagenomic sequencing. Overall, a total of 169 unique ARGs conferring resistance to 15 antimicrobial classes were detected across all sediment samples. The Kruskal-Wallis test showed that the diversity and abundance of ARGs in the UR were all significantly higher than those in the ES and BHB (p < 0.05 and p < 0.01), revealing the distance dilution of the sedimental resistomes from the river to the ocean. Multidrug resistance genes contained most of the ARG subtypes, whereas rifamycin resistance genes were the most abundant ARGs in this region. Our study demonstrated that most antimicrobial resistomes were highly accumulated in urban river sediments, whereas beta-lactamase resistance genes (mainly PNGM-1) dramatically increased away from the estuary to the open ocean. The relative abundance of mobile genetic elements (MGEs) also gradually decreased from rivers to the coastal ocean, whereas the difference in pathogenic bacteria was not significant in the three classifications. Among MGEs, plasmids were recognized as the most important carriers to support the horizontal gene transfer of ARGs within and between species. According to co-occurrence networks, pathogenic Proteobacteria, Actinobacteria, and Bacteroidetes were recognized as potential and important hosts of ARGs. Heavy metals, pH and moisture content were all recognized as the vital environmental factors influencing the distribution of ARGs in sediment samples. Overall, the present study may help to understand the distribution patterns of ARGs at a watershed scale, and help to make effective policies to control the emergence, spread and evolution of different ARG subtypes in different habitats.
Continue reading ‘Strong variation in sedimental antibiotic resistomes among urban rivers, estuaries and coastal oceans: evidence from a river-connected coastal water ecosystem in northern China’Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont
Published 26 May 2023 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, otherprocess, oxygen, physiology, prokaryotes
Introduction:
Reef building oysters provide vast ecological benefits and ecosystem services. A large part of their role in driving ecological processes is mediated by the microbial communities that are associated with the oysters; together forming the oyster holobiont. While changing environmental conditions are known to alter the physiological performance of oysters, it is unclear how multiple stressors may alter the ability of the oyster holobiont to maintain its functional role.
Methods:
Here, we exposed oysters to acidification and hypoxia to examine their physiological responses (molecular defense and immune response), changes in community structure of their associated microbial community, and changes in water nutrient concentrations to evaluate how acidification and hypoxia will alter the oyster holobiont’s ecological role.
Results:
We found clear physiological stress in oysters exposed to acidification, hypoxia, and their combination but low mortality. However, there were different physiological trade-offs in oysters exposed to acidification or hypoxia, and the combination of stressors incited greater physiological costs (i.e., >600% increase in protein damage and drastic decrease in haemocyte counts). The microbial communities differed depending on the environment, with microbial community structure partly readjusted based on the environmental conditions. Microbes also seemed to have lost some capacity in nutrient cycling under hypoxia and multi-stressor conditions (~50% less nitrification) but not acidification.
Discussion:
We show that the microbiota associated to the oyster can be enriched differently under climate change depending on the type of environmental change that the oyster holobiont is exposed to. In addition, it may be the primary impacts to oyster physiology which then drives changes to the associated microbial community. Therefore, we suggest the oyster holobiont may lose some of its nutrient cycling properties under hypoxia and multi-stressor conditions although the oysters can regulate their physiological processes to maintain homeostasis on the short-term.
Continue reading ‘Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont’Responses of biogenic dimethylated sulfur compounds to environmental changes in the northwestern Pacific continental sea
Published 11 May 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, community composition, laboratory, molecular biology, multiple factors, North Pacific, nutrients, otherprocess, phytoplankton, prokaryotes
Continental seas are facing rapid environmental shifts, but how biogenic dimethylated sulfur compounds, including dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), will respond to these environmental changes remains poorly understood. Here we investigated the effects of nutrient input, ocean acidification, and dust deposition on the phytoplankton community and organic sulfur cycle in the East China Sea. Nutrient input promoted phytoplankton growth and increased the concentrations of DMS, DMSP, and DMSO. With sufficient nutrients, especially nitrate, the dissolved DMSP degradation was inhibited, and the bacterial DMSP-cleavage pathway (inferred by dddP gene abundance) was enhanced, causing increased DMS production. The sensitivity of phytoplankton biomass and DMS to ocean acidification varied with different initial nutrient levels, demonstrating insensitivity under eutrophic conditions and negative responses under nutrient-limited conditions. The ocean acidification promoted the dissolved DMSP degradation and bacterial DMSP-demethylation pathway (inferred by dmdA gene abundance) and weakened the DMS production, causing the decreases of DMS and DMSP. The nutrient from dust deposition (2 mg L−1) was identified as the key factor in enhancing phytoplankton biomass and the organic sulfur compounds concentrations, but trace metals input from dust deposition had no significant effect. This study has identified environmental drivers and suppressors of phytoplankton and biogenic dimethylated sulfur compounds in a changing marine environment, which will enable the effective modeling of future climate change.
Continue reading ‘Responses of biogenic dimethylated sulfur compounds to environmental changes in the northwestern Pacific continental sea’Integrated FT-ICR MS and metabolome reveals diatom-derived organic matter by bacterial transformation under warming and acidification
Published 9 May 2023 Science ClosedTags: biogeochemistry, biological response, laboratory, molecular biology, multiple factors, North Pacific, physiology, prokaryotes, temperature
Highlights
- The key roles of algae-associated bacteria in the transformation of algae-derived OM.
- Bacteria have different preferences for the conversion of compounds in algae-derived OM.
- Warming and acidification affect microbial transformation of organic matter.
Summary
Bacterial transformation and processing of diatom-derived organic matter (OM) is extremely important for the cycling of production and energy in marine ecosystems; this process contributes to the production of microbial food webs. In this study, a cultivable bacterium (Roseobacter sp. SD-R1) from the marine diatom Skeletonema dohrnii were isolated and identified. A combined Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS)/untargeted metabolomics approach was used to synthesize the results of bacterial transformation with dissolved OM (DOM) and lysate OM (LOM) under warming and acidification through laboratory experiments. Roseobacter sp. SD-R1 had different preferences for the conversion of molecules in S. dohrnii-derived DOM and LOM treatments. The effects of warming and acidification contribute to the increased number and complexity of molecules of carbon, hydrogen, oxygen, nitrogen, and sulfur after the bacterial transformation of OM. The chemical complexity generated by bacterial metabolism provides new insights into the mechanisms that shape OM complexity.
Continue reading ‘Integrated FT-ICR MS and metabolome reveals diatom-derived organic matter by bacterial transformation under warming and acidification’Acidification alters sediment nitrogen source-sink dynamics in eelgrass (Zostera marina (L.)) beds
Published 9 May 2023 Science ClosedTags: biogeochemistry, biological response, BRcommunity, laboratory, morphology, nitrogen fixation, North Atlantic, phanerogams, physiology, prokaryotes, sediment
Dissolved carbon dioxide (CO2) in seawater lowers water pH and can disrupt microbial nutrient cycles. It is unclear how acidification impacts hot spots of nutrient cycling in marine ecosystems such as eelgrass (Zostera marina) beds. We measured nutrient and gas fluxes in sediment cores from Z. marina beds and unvegetated-sediment habitats in Shinnecock Bay, New York, USA in a continuous-flow system with acidified and ambient pH treatments. Under ambient conditions, uptake of N2 by nitrogen (N) fixation was greater than production of N2 by denitrification. Denitrification, however, was dominant under acidified conditions. We then enriched flowing seawater with 15NO3− to test the impact of a nutrient pulse with ambient pH or acidified conditions in the eelgrass and unvegetated cores. Sediment N2 efflux was higher in eelgrass than unvegetated sediments under acidified pH with N-enriched treatments. Results suggest that eelgrass beds may serve as sinks rather than sources of N under the combined stressors of acidification and N-loading. Documenting changes to N pathways under acidification can inform efforts to manage marine ecosystems and conserve benthic habitats.
Continue reading ‘Acidification alters sediment nitrogen source-sink dynamics in eelgrass (Zostera marina (L.)) beds’Addressing the joint impact of temperature and pH on Vibrio harveyi adaptation in the time of climate change
Published 27 April 2023 Science ClosedTags: abundance, biological response, growth, laboratory, morphology, mortality, otherprocess, prokaryotes
Global warming and acidification of the global ocean are two important manifestations of the ongoing climate change. To characterize their joint impact on Vibrio adaptation and fitness, we analyzed the temperature-dependent adaptation of Vibrio harveyi at different pHs (7.0, 7.5, 8.0, 8.3 and 8.5) that mimic the pH of the world ocean in the past, present and future. Comparison of V. harveyi growth at 20, 25 and 30 °C show that higher temperature per se facilitates the logarithmic growth of V. harveyi in nutrient-rich environments in a pH-dependent manner. Further survival tests carried out in artificial seawater for 35 days revealed that cell culturability declined significantly upon incubation at 25 °C and 30 °C but not at 20 °C. Moreover, although acidification displayed a negative impact on cell culturability at 25 °C, it appeared to play a minor role at 30 °C, suggesting that elevated temperature, rather than pH, was the key player in the observed reduction of cell culturability. In addition, analyses of the stressed cell morphology and size distribution by epifluorescent microscopy indicates that V. harveyi likely exploits different adaptation strategies (e.g., acquisition of coccoid-like morphology) whose roles might differ depending on the temperature–pH combination.
Continue reading ‘Addressing the joint impact of temperature and pH on Vibrio harveyi adaptation in the time of climate change’Ocean acidification has a strong effect on communities living on plastic in mesocosms
Published 26 April 2023 Science ClosedTags: abundance, biological response, BRcommunity, chemistry, community composition, field, gastrotricha, mesocosms, molecular biology, nitrogen fixation, North Pacific, otherprocess, prokaryotes, protists
We conducted a mesocosm experiment to examine how ocean acidification (OA) affects communities of prokaryotes and eukaryotes growing on single-use drinking bottles in subtropical eutrophic waters of the East China Sea. Based on 16S rDNA gene sequencing, simulated high CO2 significantly altered the prokaryotic community, with the relative abundance of the phylum Planctomycetota increasing by 49%. Under high CO2, prokaryotes in the plastisphere had enhanced nitrogen dissimilation and ureolysis, raising the possibility that OA may modify nutrient cycling in subtropical eutrophic waters. The relative abundance of pathogenic and animal parasite bacteria also increased under simulated high CO2. Our results show that elevated CO2 levels significantly affected several animal taxa based on 18S rDNA gene sequencing. For example, Mayorella amoebae were highly resistant, whereas Labyrinthula were sensitive to OA. Thus, OA may alter plastisphere food chains in subtropical eutrophic waters.
Scientific Significance Statement
Plastic waste in the ocean is an urgent environmental concern and has given rise to a novel habitat, known as the “plastisphere.” Under ocean acidification (OA), changes in plastisphere community composition may alter plastic degradation, deposition, and passage through food webs, but these have not been studied yet. This is the first study about the effects of simulated high CO2 on the plastisphere using a mesocosm. We discovered that after 1 month the beta diversity of prokaryotic communities living on single-use plastic drinking bottles was significantly different under different carbon dioxide concentrations, with more pathogens at high CO2. Based on function prediction analysis, the relative abundance of bacterial taxa involved in nitrogen and nitrate respiration and ureolysis was significantly higher under simulated high CO2. We conclude that OA has significant effects on the plastisphere and its predicted functions.
Continue reading ‘Ocean acidification has a strong effect on communities living on plastic in mesocosms’Ocean acidification alters the benthic biofilm communities in intertidal soft sediments
Published 17 April 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, community composition, growth, laboratory, molecular biology, North Pacific, otherprocess, photosynthesis, physiology, prokaryotes, sediment
Microphytobenthos (MPB) and bacterial biofilms play crucial roles in primary and secondary production, nutrient cycling and invertebrate settlement in coastal ecosystems, yet little is known of the effects of ocean acidification (OA) on these communities in intertidal soft sediments. To fill in this gap, a 28-day CO2 enhancement experiment was conducted for the benthic biofilms in soft intertidal sediments (muds and sands) from Qingdao, China. This experiment included three CO2 treatments: 400 ppm CO2 (control), 700 ppm CO2 and 1000 ppm CO2 (IPCC predicted value in 2100), which were established in a three-level CO2 incubator that can adjust the CO2 concentration in the overlying air. The effects of OA on benthic biofilms were assessed in the following three aspects: MPB biomass, biofilm community structure and microbial biogeochemical cycling (e.g., C-cycle, N-cycle and S-cycle). This study found that the 700 ppm CO2 treatment did not significantly affect the benthic biofilms in intertidal soft sediments, but the 1000 ppm CO2 treatment significantly altered the biofilm community composition and potentially their role in microbial biogeochemical cycling in sediments (especially in sandy sediments). For the bacterial community in biofilms, the 1000 ppm CO2 enhancement increased the relative abundance of Alteromonadales and Bacillales but decreased the relative abundance of Rhodobacterales and Flavobacteriales. For microbial biogeochemical cycling, the 1000 ppm CO2 treatment enhanced the potential of chemoheterotrophic activity, nitrate reduction and sulfur respiration in sediments, likely resulting in a more stressful environment (hypoxic and enriched H2S) for most benthic organisms. Even though incubations in this study were only 28 days long and thus couldn’t fully accommodate the range of longer-term adaptions, it still suggests that benthic biofilms in intertidal sandy sediments are likely to change significantly near the end of the century if anthropogenic CO2 emissions unmitigated, with profound implications on local ecosystems and biogeochemical cycling.
Continue reading ‘Ocean acidification alters the benthic biofilm communities in intertidal soft sediments’Two treatment methods on Ulva prolifera bloom result in distinctively different ecological effects in coastal environment
Published 14 April 2023 Science ClosedTags: abundance, algae, biological response, BRcommunity, community composition, laboratory, molecular biology, morphology, North Atlantic, otherprocess, prokaryotes
Green tides Ulva prolifera have broken out in the Yellow Sea for more than 10 years, becoming a periodic ecological disaster. The largest-ever green tide that occurred in 2021 promoted innovation in treatment methods. Different from the traditional harvest-disposal method, a microbial complex formulation was firstly sprayed on the harvest U. prolifera that promotes rapid degradation, and then fermented and disposed into the sea. At present, little was known about the ecological effects of those different treatment methods. In order to examine this hypothesis, we run an in-lab incubation of 60 days to simulate the two methods to degrade U. prolifera, with focuses on the degradation ensued impacts on water quality. The degradation process of fresh U. prolifera over two months was dominated by the continuous and slow release of DOM, and the concentration of DOM in the water column was hardly observed to decrease within two months. The pre-discomposed-disposal method also significantly altered microbial community structure. The pre-decomposing treatment with microbial complex formulations destroyed U. prolifera cell tissues and changed its physical state in seawater from floating to fast depositing, and increased the degradation rate by about 14 times. The rapid decomposition of the released bioactive organic matter consumed a substantial amount of dissolved oxygen in local seawater, which has the potential risk of causing local hypoxia and acidification in a short-term. The pre-decomposition treatment of U. prolifera could be a practical and efficient countermeasures to U. prolifera blooming. After the complete degradation of the pre-decomposed U. prolifera, the resulting dissolved organic matter could increase TA to resist acidification. Overall, compared with traditional harvest-packing-disposal method, the pre-decomposing-disposal treatment is an efficient and environmental-friendly disposal method to deal with the U. prolifera “green tide”, but it should be used cautiously.
Continue reading ‘Two treatment methods on Ulva prolifera bloom result in distinctively different ecological effects in coastal environment’
