Carbon Fixation Potential Research Articles

Carbon-fixing bacteria in diverse groundwaters of karst area: Distribution patterns, ecological interactions, and driving factors

The biological carbon pump in karst areas is of great significance for maintaining the effectiveness of karst carbon sinks. However, the spatial distribution and carbon-fixing potential of microorganisms in different aquifers within karst areas remain poorly understood. In this study, the distribution patterns, ecological roles, and environmental drivers of microbiota associated with CO2 fixation were investigated in karst groundwater (KW), porous groundwater (PW), fractured groundwater (FW), and surface water (SW) within a typical karst watershed, located in Guilin, southwest China. KW, PW, and FW displayed the similar community structure and indicative carbon-fixing bacteria composition, which were dominated by chemoautotrophic bacteria compared to SW. Higher abundances of indicative carbon-fixing bacteria and carbon-fixing genes, as well as richer proportions of microbial-derived DOC, indicated the more significant microbial carbon-fixing potential in KW and PW. At the profile of KW, a carbon-fixing hotspot was discovered at the depths of 0–50 m. Correlation analysis between carbon-fixing bacteria and DOC revealed that the chemoautotrophic process driven by nitrogen and sulfur oxidation predominated the microbial carbon fixation in groundwater. Co-occurrence network analysis demonstrated that carbon-fixing bacteria exhibited cooperation with other bacterial taxa in KW, while competition was the dominant interaction in PW. Moreover, carbon-fixing bacteria was found to lead bacterial assembly more deterministic in KW. The analysis of environmental factors and microbial diversity illustrated that inorganic carbon and redox state drove community variations across groundwaters. Structural equation model (SEM) further confirmed that ORP was the primary factor influencing the carbon fixation potential. This study provides a new insight into biological carbon fixation in karst aquatic systems, which holds significance in the accurate assessment of karst carbon sinks.

Rubisco in high Arctic tidewater glacier‐marine systems: A new window into phytoplankton dynamics

AbstractThe hundreds of tidewater glaciers found in the Canadian Arctic Archipelago have the potential to enhance delivery of nutrients and other material to the surface ocean. Despite this, their influence on marine ecosystems, specifically phytoplankton, is poorly characterized. Here we developed and applied a quantitative mass spectrometry‐based approach to measure phytoplankton ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) concentrations to examine differences in productivity in glacierized and non‐glacierized marine systems in Jones Sound, Nunavut, within Inuit Nunangat. Comparisons to chloroplast 16S rRNA gene amplicon sequencing data suggested that these measurements detect the majority of Rubisco produced in Jones Sound. Because Rubisco catalyzes carbon fixation, we used these measurements to estimate total and group‐specific primary production potential, which were within the range of historical primary production measurements made using classical methods in this region. Our measurements also revealed that up to 2% of total protein in the water column is Rubisco, and that Rubisco concentrations are correlated with chlorophyll fluorescence, with maxima near the nitracline. Rubisco produced by diatom genera Chaetoceros and Thalassiosira were higher in marine regions influenced by glaciers, while Rubisco from Micromonas (Chlorophyta) was greater in non‐glacierized regions. This suggests that future climate scenarios may favor smaller phytoplankton groups, like Micromonas, with consequences for food webs and carbon cycling. This study broadens our understanding of how tidewater glaciers will impact phytoplankton communities, now and in a warmer future, and lays the foundation for using this mass spectrometry‐based approach to quantify phytoplankton group‐specific carbon fixation potential in other marine regions.

In situ community transcriptomics illuminates CO2-fixation potentials and supporting roles of phagotrophy and proton pump in plankton in a subtropical marginal sea.

Lineage-wise physiological activities of plankton communities in the ocean are important but challenging to characterize. Here, we conducted whole-assemblage metatranscriptomic profiling at continental shelf and slope sites in the South China Sea to investigate carbon fixation potential in different lineages. RuBisCO expression, the proxy of Calvin carbon fixation (CCF) potential, was mainly contributed by Bacillariophyta, Chlorophyta, Cyanobacteria, and Haptophyta, which was differentially affected by environmental factors among lineages. CCF potential exhibited positive or negative correlations with phagotrophy gene expression, suggesting phagotrophy possibly enhances or complements CCF. Our data also reveal significant non-Calvin carbon fixation (NCF) potential, as indicated by the active expression of genes in all five currently recognized NCF pathways, mainly contributed by Flavobacteriales, Alteromonadales, and Oceanospirillales. Furthermore, in Flavobacteriales, Alteromonadales, Pelagibacterales, and Rhodobacterales, NCF potential was positively correlated with proton-pump rhodopsin (PPR) expression, suggesting that NCF might be energetically supported by PPR. The novel insights into the lineage-differential potential of carbon fixation, widespread mixotrophy, and PPR as an energy source for NCF lay a methodological and informational foundation for further research to understand carbon fixation and the trophic landscape in the ocean.IMPORTANCEMarine plankton plays an important role in global carbon cycling and climate regulation. Phytoplankton and cyanobacteria fix CO2 to produce organic compounds using solar energy and mainly by the Calvin cycle, whereas autotrophic bacteria and archaea may fix CO2 by non-Calvin cycle carbon fixation pathways. How active individual lineages are in carbon fixation and mixotrophy, and what energy source bacteria may employ in non-Calvin carbon fixation, in a natural plankton assemblage are poorly understood and underexplored. Using metatranscriptomics, we studied carbon fixation in marine plankton with lineage resolution in tropical marginal shelf and slope areas. Based on the sequencing results, we characterized the carbon fixation potential of different lineages and assessed Calvin- and non-Calvin- carbon fixation activities and energy sources. Data revealed a high number of unigenes (4.4 million), lineage-dependent differential potentials of Calvin carbon fixation and responses to environmental conditions, major contributors of non-Calvin carbon fixation, and their potential energy source.

Novel database for accA gene revealed a vertical variability pattern of autotrophic carbon fixation potential of ammonia oxidizing archaea in a permeable subterranean estuary

The autotrophic carbon fixation pathway of ammonia-oxidizing archaea (AOA) was the 3-hydroxypropionate/4-hydroxybutyrate (3-HP/4-HB) cycle, of which the acetyl-CoA carboxylase α-submit (accA) gene is widely recognized as the indicator. To date, there is no reference database or suitable cut-off value for operational taxonomic unit (OTU) clustering to analyze the diversity of AOA based on the accA gene. In this study, a reference database with 489 sequences was constructed, all the accA gene sequences was obtained from the AOA enrichment culture, pure culture and environmental samples. Additionally, the 79% was determined as the cut-off value for OTU clustering by comparing the similarity between the accA gene and the 16S rRNA gene. The developed method was verified by analyzing samples from the subterranean estuary and a vertical variation pattern of autotrophic carbon fixation potential of AOA was revealed. This study provided an effective method to analyze the diversity and autotrophic carbon fixation potential of AOA based on accA gene.

Functional redundancy is the key mechanism used by microorganisms for nitrogen and sulfur metabolism during manure composting

The microbial ecological functions associated with the nitrogen and sulfur cycles during composting have not been thoroughly elucidated. Using metagenomic sequencing, the microbial mechanisms underlying the nitrogen and sulfur metabolism during livestock and poultry manure composting were investigated in this study. The findings demonstrate that functional redundancy among microorganisms is a crucial factor for the nitrogen and sulfur cycling during livestock and poultry manure composting. Processes such as organic sulfur synthesis, assimilatory sulfate reduction, ammonia assimilation, and denitrification were found to be prevalent. Additionally, there was a certain degree of conservation in nitrogen and sulfur conversion functions among microorganisms at the phylum level. All high-quality metagenomic assembly genomes (MAGs) possessed carbon fixation potential, with 86.3 % of MAGs containing both nitrogen and sulfur conversion genes. Except for bin30, other MAGs encoding sulfur oxidation enzymes were found to be associated with at least one denitrification gene. This suggests a potential interplay between nitrogen and sulfur metabolism among microorganisms. 45, 19, 1, 31, 1, and 2 MAGs could completely regulate organic sulfur synthesis, assimilatory sulfate reduction, thiosulfate oxidation to sulfate, glutamine synthase-glutamate synthase pathway (GS-GOGAT), denitrification, and dissimilatory nitrate reduction, respectively by encoding the required enzymes. TN and pH were the key factors driving the functional redundancy in nitrogen and sulfur microbial community.

Metagenome-based analysis of carbon-fixing microorganisms and their carbon-fixing pathways in deep-sea sediments of the southwestern Indian Ocean.

Carbon fixation by chemoautotrophic microorganisms in the dark ocean makes a large contribution to oceanic primary production and the global carbon cycle. In contrast to the Calvin cycle-dominated carbon-fixing pathway in the marine euphotic zone, carbon-fixing pathways and their hosts in deep-sea areas are diverse. In this study, four deep-sea sediment samples close to hydrothermal vents in the southwestern Indian Ocean were collected and processed using metagenomic analysis to investigate carbon fixation potential. Functional annotations revealed that all six carbon-fixing pathways had genes to varied degrees present in the samples. The reductive tricarboxylic acid cycle and Calvin cycle genes occurred in all samples, in contrast to the Wood-Ljungdahl pathway, which previous studies found mainly in the hydrothermal area. The annotations also elucidated the chemoautotrophic microbial members associated with the six carbon-fixing pathways, and the majority of them containing key carbon fixation genes belonged to the phyla Pseudomonadota and Desulfobacterota. The binned metagenome-assembled genomes revealed that key genes for the Calvin cycle and the 3-hydroxypropionate/4-hydroxybutyrate cycle were also found in the order Rhodothermales and the family Hyphomicrobiaceae. By identifying the carbon metabolic pathways and microbial populations in the hydrothermal fields of the southwest Indian Ocean, our study sheds light on complex biogeochemical processes in deep-sea environments and lays the foundation for further in-depth investigations of carbon fixation processes in deep-sea ecosystems.

Phytoplankton Carbon Utilization Strategies and Effects on Carbon Fixation

Phytoplankton have a crucial role in the conversion of greenhouse gas sources and sinks in natural water bodies, such as lakes, rivers, and oceans. In response to environmental changes, phytoplankton adapt by altering their carbon utilization strategies, which affect carbon fixation rates and carbon fluxes at the water–air interface. This paper classifies and summarizes the main carbon utilization strategies of phytoplankton in terms of carbon acquisition, carbon metabolism, and carbon emission. Their carbon acquisition strategy determines their carbon uptake rate, while their carbon metabolism strategy affects their carbon fixation potential. Moreover, their carbon emission strategy determines the final net carbon fixation. A systematic study of phytoplankton carbon utilization strategies is important for the development of phytoplankton-based wastewater treatment technologies, understanding of algal greenhouse gas fixation, and assessment of greenhouse gas sources and sinks in natural water bodies. This article provides a comprehensive understanding of the ecological role of phytoplankton in natural water bodies and offers valuable references for related research. Furthermore, our research sheds light on the carbon metabolism and emission processes of phytoplankton. By analyzing the carbon metabolism and emission of phytoplankton under different carbon utilization strategies, we can more accurately evaluate the impact of phytoplankton on the carbon cycle in natural water bodies, which can contribute to environmental protection and sustainable development.

Liquid-solid ratio during hydrothermal carbonization affects hydrochar application potential in soil: Based on characteristics comparison and economic benefit analysis

Returning straw-like agricultural waste to the field by converting it into hydrochar through hydrothermal carbonization (HTC) is an important way to realize resource utilization of waste, soil improvement, and carbon sequestration. However, the large-scale HTC is highly limited by the large water consumption and waste liquid pollution. Here, we propose strategies to optimize the liquid-solid ratio (LSR) of HTC, and comprehensively evaluate the stability, soil application potential, and economic benefits of corn stover-based hydrochar under different LSRs. The results showed that the total amount of dissolved organic carbon of hydrochars increased by 55.0% as LSR reducing from 10:1 to 2:1, while the element content, thermal stability, carbon fixation potential, specific surface area, pore volume, and functional group type were not obviously affected. The specific surface area and pore volume of hydrochar decreased by 61.8% and 70.9% as LSR reduced to 1:1, due to incomplete carbonization. According to the gray relation, hydrochar derived at LSR of 10:1 and followed by 2:1 showed greatest relation degree of 0.80 and 0.70, respectively, indicating better soil application potential. However, reducing LSR from 10:1 to 2:1 made the income of single process production increased from −388 to 968 ¥, and the wastewater generation decreased by 80%. Considering the large-scale application of HTC in fields for farmland improvement and environmental remediation, the comprehensive advantages of optimized LSR will be further highlighted.

Quantitative Proteomic Analysis Reveals the Key Molecular Events Driving Phaeocystis globosa Bloom and Dissipation.

Phaeocystis globosa is a marine-bloom-forming haptophyte with a polymorphic life cycle alternating between free-living cells and a colonial morphotype, that produces high biomass and impacts ecological structure and function. The mechanisms of P. globosa bloom formation have been extensively studied, and various environmental factors are believed to trigger these events. However, little is known about the intrinsic biological processes that drive the bloom process, and the mechanisms underlying P. globosa bloom formation remain enigmatic. Here, we investigated a P. globosa bloom occurring along the Chinese coast and compared the proteomes of in situ P. globosa colonies from bloom and dissipation phases using a tandem mass tag (TMT)-based quantitative proteomic approach. Among the 5540 proteins identified, 191 and 109 proteins displayed higher abundances in the bloom and dissipation phases, respectively. The levels of proteins involved in photosynthesis, pigment metabolism, nitrogen metabolism, and matrix substrate biosynthesis were distinctly different between these two phases. Ambient nitrate is a key trigger of P. globosa bloom formation, while the enhanced light harvest and multiple inorganic carbon-concentrating mechanisms support the prosperousness of colonies in the bloom phase. Additionally, colonies in the bloom phase have greater carbon fixation potential, with more carbon and energy being fixed and flowing toward the colonial matrix biosynthesis. Our study revealed the key biological processes underlying P. globosa blooms and provides new insights into the mechanisms behind bloom formation.

Niche differentiation of ammonia-oxidizing archaea and related autotrophic carbon fixation potential in the water column of the South China Sea

SummaryThe significant primary production by ammonia-oxidizing archaea (AOA) in the ocean was reported, but the carbon fixation process of AOA and its community composition along the water depth remain unclear. Here, we investigated the abundance, community composition, and potential carbon fixation of AOA in water columns of the South China Sea. Higher abundances of the amoA and accA genes of AOA were found below the euphotic zone. Similarly, higher carbon fixation potential of AOA, evaluated by the ratios of amoA to accA gene, was also observed below euphotic zone and the ratios increased with increasing water depth. The vertical niche differentiation of AOA was further evidenced, with the dominant genus shifting from Nitrosopelagicus in the epipelagic zone to uncultured genus in the meso- and bathypelagic zones. Our findings highlight the higher carbon fixation potential of AOA in deep water and the significance of AOA to the ocean carbon budget.

我国植被生态系统固碳能力提升潜力空间格局研究

PDF HTML阅读 XML下载 导出引用 引用提醒 我国植被生态系统固碳能力提升潜力空间格局研究 DOI: 10.5846/stxb202107171928 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发专项项目（2021YFB3901102，2021YFB2600101） Spatial pattern analysis of carbon sequestration potential of vegetation ecosystem in China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:通过植被的光合作用对大气中的CO2进行收集与捕捉是当前实现"碳中和"目标的重要手段，目前的研究大多是聚焦于当前植被的固碳能力的强弱，而对于当下植被固碳能力提升潜力大小的研究相对较少。为此，基于1982-2017年全球陆表特征参量-植被净初级生产力（GLASS NPP）产品以及Miami模型分别构建遥感观测和气候模型模拟的全国NPP潜在最大值空间分布结果，通过与2017年实际监测的NPP进行比较，计算得到两种不同的全国植被固碳能力提升潜力结果，分别进行空间特征分析，并对比两者冷热点区域空间分布的差异性，最后与我国目前规划的重点生态功能区进行叠加对比，得出以下主要结论：（1）两种方法得到的全国固碳能力提升潜力空间分布整体趋势均表现为"南高北低"，且空间分布特征呈现出高度空间自相关特性（空间正相关性，表现为"高高聚集" "低低聚集" ），但局部差异较大。（2）基于遥感观测为最大潜力值的方法所得到的全国固碳能力提升潜力热点区集中在三个区域，分别分布在四川省、广东省、浙江省以及江苏省境内。基于气候模型模拟为最大潜力值的方法所得到的固碳能力提升潜力热点区域主要分布在以江西省、广东省、广西省为核心的南方8个省份。（3）当前我国重点生态功能区的碳固定潜能并不突出，因此建议有关部门在今后的政策制定过程中将这一方面也加以考虑。 Abstract:Nowadays, the global CO2 emissions have seriously exceeded the standard, and the resulting greenhouse effect has seriously affected people's production and life. Collecting and capturing CO2 in the atmosphere through vegetation photosynthesis is an important means to achieve the goal of carbon neutralization. Most of the studies focus on the current strength of vegetation carbon sequestration capacity, while there are few studies on the vegetation carbon sequestration potential. In fact, the improvement potential of vegetation carbon sequestration capacity also has important guiding significance for the goal of carbon neutralization. Therefore, this paper constructs the spatial distribution results of national Net Primary Productivity(NPP) maximum potential based on remote sensing observation product GLASS NPP and Miami climate model from 1982 to 2017. By comparing with the actual monitored NPP in 2017, two different national vegetation carbon sequestration potential results are calculated. In order to compare the spatial heterogeneity of the results. The spatial distribution characteristics of the two results are analyzed respectively, and the differences of the spatial distribution of cold and hot spots are compared. Finally, the results are superimposed and compared with the key ecologically functional areas currently planned in China, provide scientific basis for national policy-making. The following main conclusions are drawn:(1) The overall spatial distribution trend of the national vegetation carbon sequestration potential obtained by the two methods is high in the south and low in the north. The spatial distribution characteristics show high spatial autocorrelation characteristics (The main performance is spatial positive correlation, manifested as high-high aggregation and low-low aggregation), but the local difference is large. (2) Based on the method of remote sensing observation as the maximum potential value, the national vegetation carbon sequestration potential hot spots areas are concentrated in three regions, which are distributed in Sichuan Province, Guangdong Province, Zhejiang Province and Jiangsu Province, respectively. Based on the climate model simulation as the maximum potential value, the hot spots of vegetation carbon sequestration potential are mainly distributed in eight southern provinces with Jiangxi Province, Guangdong Province and Guangxi Province as the core. Both results show the characteristics of high spatial aggregation (3) At present, the carbon fixation potential of key ecological functional areas in China is not prominent, so it is suggested that relevant departments should also consider this aspect in the future policy-making process. In general, this paper can provide a reference for the related research of vegetation carbon sequestration level and the realization of carbon neutralization goal in China. 参考文献 相似文献 引证文献

Leave no stone unturned: individually adapted xerotolerant Thaumarchaeota sheltered below the boulders of the Atacama Desert hyperarid core

BackgroundThe hyperarid core of the Atacama Desert is an extremely harsh environment thought to be colonized by only a few heterotrophic bacterial species. Current concepts for understanding this extreme ecosystem are mainly based on the diversity of these few species, yet a substantial area of the Atacama Desert hyperarid topsoil is covered by expansive boulder accumulations, whose underlying microbiomes have not been investigated so far. With the hypothesis that these sheltered soils harbor uniquely adapted microbiomes, we compared metagenomes and geochemistry between soils below and beside boulders across three distantly located boulder accumulations in the Atacama Desert hyperarid core.ResultsGenome-resolved metagenomics of eleven samples revealed substantially different microbial communities in soils below and beside boulders, despite the presence of shared species. Archaea were found in significantly higher relative abundance below the boulders across all samples within distances of up to 205 km. These key taxa belong to a novel genus of ammonia-oxidizing Thaumarchaeota, Candidatus Nitrosodeserticola. We resolved eight mid-to-high quality genomes of this genus and used comparative genomics to analyze its pangenome and site-specific adaptations. Ca. Nitrosodeserticola genomes contain genes for ammonia oxidation, the 3-hydroxypropionate/4-hydroxybutyrate carbon fixation pathway, and acetate utilization indicating a chemolithoautotrophic and mixotrophic lifestyle. They also possess the capacity for tolerating extreme environmental conditions as highlighted by the presence of genes against oxidative stress and DNA damage. Site-specific adaptations of the genomes included the presence of additional genes for heavy metal transporters, multiple types of ATP synthases, and divergent genes for aquaporins.ConclusionWe provide the first genomic characterization of hyperarid soil microbiomes below the boulders in the Atacama Desert, and report abundant and highly adapted Thaumarchaeaota with ammonia oxidation and carbon fixation potential. Ca. Nitrosodeserticola genomes provide the first metabolic and physiological insight into a thaumarchaeal lineage found in globally distributed terrestrial habitats characterized by various environmental stresses. We consequently expand not only the known genetic repertoire of Thaumarchaeota but also the diversity and microbiome functioning in hyperarid ecosystems.7Emv5x2zFsLcvyRTYGWyYKVideo

The dominant microbial metabolic pathway of the petroleum hydrocarbons in the soil of shale gas field: Carbon fixation instead of CO2 emissions

In shale gas mining areas, indigenous microorganisms degrade organic pollutants such as petroleum hydrocarbons into carbon dioxide (CO2) and water (H2O) through aerobic metabolism. A large quantity of CO2 emissions will exacerbate the “Greenhouse effect”. Based on the clean sieved soil and oil-based drilling fluid in the shale gas mining area, this experiment set three concentration gradients (3523 ± 159 mg/kg, 8715 ± 820 mg/kg and 22,031 ± 1533 mg/kg) to treat the soil, and each group was disposed for the same amount of time (63 days). By analyzing the dynamic changes of microbial diversity and the abundance of key functional genes for carbon fixation, the impact of petroleum hydrocarbons on carbon fixation potential was discovered, and the natural attenuation law of petroleum hydrocarbons in contaminated soil was explored. It provided the scientific research basis of ecology for the carbon cycle, carbon allocation, and carbon fixation in microbial remediation of petroleum hydrocarbon contaminated soil. The results obtained indicated the following: i) The removal rate of petroleum hydrocarbons under high-concentration pollution (45.33 ± 3.90%) was significantly lower than low and medium-concentration pollution. The TPH concentration removal rate of each group was the largest in the early stage of culture (1-5d), and there was no significant correlation between the TPH content and the community composition (R2 = 0.0736, P > 0.05). ii) Composition and function of Carbon Fixation associated microbiota were assessed by 16S rRNA sequencing and PICRUSt (phylogenetic investigation of communities by reconstruction of unobserved states) analysis. The main carbon fixation pathway in this study is the reductive citric acid cycle, because there was no shortage of enzymes that can affect subsequent reactions.

New insight into soil carbon fixation rate: The intensive co-occurrence network of autotrophic bacteria increases the carbon fixation rate in depositional sites

Whilst it has been shown that different microbial populations can significantly affect ecosystem functions, little is known about the potential effect of soil erosion on autotrophic bacterial co-occurrence networks and if the networks can influence carbon fixation potential. Here, the random matrix theory (RMT)-based molecular ecological network (MEN) approach with a stable isotope labeling experiment were performed to discern the relationship between autotrophic bacterial networks with the carbon fixing ability and quantify the 13CO2 (carbon dioxide) fixation rate in different soil erosion regions (the Chinese Loess Plateau, the T groups, and the hilly red soil erosion region in Southern China, the H groups). The rates of carbon fixation (RS) were ranked in the following order: H group depositional sites (HD; 30.86 Mg C km−2 yr−1) > H group erosion sites (HE; 18.04 Mg C km−2 yr−1) > T group depositional sites (TD; 5.00 Mg C km−2 yr−1) > T group erosion sites (TE; 1.03 Mg C km−2 yr−1). The results of the random forest modeling and variation partitioning analysis indicated that the bacterial co-occurrence networks were significantly associated with the carbon fixation rate (P < 0.05), and can explain 85.9% variations of carbon fixation rate in different erosion and deposition sites. With the results of multiple stepwise linear regression analysis, pH and C: N were considered to be the key abiotic factors that influenced the carbon fixing rate, which resulted in the carbon fixation rate of H groups were higher than what in T groups. Further, the ZP-plot suggested that the Proteobacteria were the keystones connecting and promoting other species to perform the C-fixing function. The statistical evidence of co-occurrence networks, which are positively associated with the autotrophic bacterial carbon fixation rate, advances the understanding of microbial networks in the function of carbon fixation.

Influence of the polar light cycle on seasonal dynamics of an Antarctic lake microbial community

BackgroundCold environments dominate the Earth’s biosphere and microbial activity drives ecosystem processes thereby contributing greatly to global biogeochemical cycles. Polar environments differ to all other cold environments by experiencing 24-h sunlight in summer and no sunlight in winter. The Vestfold Hills in East Antarctica contains hundreds of lakes that have evolved from a marine origin only 3000–7000 years ago. Ace Lake is a meromictic (stratified) lake from this region that has been intensively studied since the 1970s. Here, a total of 120 metagenomes representing a seasonal cycle and four summers spanning a 10-year period were analyzed to determine the effects of the polar light cycle on microbial-driven nutrient cycles.ResultsThe lake system is characterized by complex sulfur and hydrogen cycling, especially in the anoxic layers, with multiple mechanisms for the breakdown of biopolymers present throughout the water column. The two most abundant taxa are phototrophs (green sulfur bacteria and cyanobacteria) that are highly influenced by the seasonal availability of sunlight. The extent of the Chlorobium biomass thriving at the interface in summer was captured in underwater video footage. The Chlorobium abundance dropped from up to 83% in summer to 6% in winter and 1% in spring, before rebounding to high levels. Predicted Chlorobium viruses and cyanophage were also abundant, but their levels did not negatively correlate with their hosts.ConclusionOver-wintering expeditions in Antarctica are logistically challenging, meaning insight into winter processes has been inferred from limited data. Here, we found that in contrast to chemolithoautotrophic carbon fixation potential of Southern Ocean Thaumarchaeota, this marine-derived lake evolved a reliance on photosynthesis. While viruses associated with phototrophs also have high seasonal abundance, the negative impact of viral infection on host growth appeared to be limited. The microbial community as a whole appears to have developed a capacity to generate biomass and remineralize nutrients, sufficient to sustain itself between two rounds of sunlight-driven summer-activity. In addition, this unique metagenome dataset provides considerable opportunity for future interrogation of eukaryotes and their viruses, abundant uncharacterized taxa (i.e. dark matter), and for testing hypotheses about endemic species in polar aquatic ecosystems.3rEAa4a8EPvdQSJ1TDqSyzVideo

Oxalotrophic bacterial assemblages in the ectomycorrhizosphere of forest trees and their effects on oxalate degradation and carbon fixation potential

Ectomycorrhizal (ECM) fungi can promote soil mineral weathering through acidification and complexation by secreting oxalic acid. However, the metabolism of oxalate in the ectomycorrhizosphere and identity of the bacteria involved are still poorly understood. Here, we investigated the abundance and community structure of oxalotrophic bacteria in the ectomycorrhizospheres of Pinus massoniana and Quercus serrata trees using quantitative PCR and high-throughput sequencing. The secondary minerals formed in the degradation of oxalate were analyzed using SEM, XRD and HRTEM. Our results showed that oxalotrophic bacteria are abundant in the ectomycorrhizosphere (2.60–5.03 × 108/g soil) and that ECM fungi can influence oxalotrophic bacteria, resulting in communities that are compositionally distinct from those in non-mycorrhizosphere soils. The results also showed that approximately one third of these bacterial species were nitrogen-fixing, accounting for 43–60% of the total sequences of oxalotrophic bacteria. An oxalotrophic Streptomyces sp. NJ10 was isolated from the ectomycorrhizosphere of P. massoniana and shown to be able to degrade calcium oxalate and induce the formation of carbonate minerals (calcite or dolomite). This study provides novel evidence that ECM fungi can enrich specific oxalotrophic bacteria in the ectomycorrhizosphere, that degrade oxalate using the oxalate-carbonate pathway, representing a potential long-term sink for photosynthetically fixed carbon derived from the atmosphere. These findings improve our understanding of the possible ecological functioning and environmental effects of plant-fungal-bacterial interactions in forests.

Carbon fixation properties of three alkalihalophilic microalgal strains under high alkalinity

Carbon dioxide (CO2) recovery with high alkalinity microalgal culture is expected to be an energy-efficient and environmentally friendly process. To increase the CO2 recovery efficiency, selection of rapidly growing alkalihalophilic microalgae is necessary. This study optimized the culture conditions of three species of alkalihalophilic microalgae, Arthrospira platensis, Dunaliella salina, and Euhalothece sp., and compared their CO2 fixation potential. Although D. salina tolerated relatively high dissolved inorganic carbon (DIC; 0.50 mol L−1), its carbon fixation rate was found to be slower than the other two species. The two cyanobacteria, A. platensis and Euhalothece sp., favored high pH (9.8–10) and high DIC (0.23–1.1 mol L−1). Euhalothece sp. grew in the highest alkalinity, resulting in the strongest pH buffer against acidification during CO2 absorption. However, the carbon fixation properties of A. platensis and Euhalothece sp. under the same light condition were found to be similar (33 and 35 mmol L−1 day−1). These results indicate that the carbon fixation potential per medium inorganic carbon was higher in A. platensis than in the others. Arthrospira platensis was found to be favorable in a CO2 recovery process unless extremely high pH stability is needed.

Carbon storage potential of avenue trees: a comparison of Barringtonia racemosa, Cyclobalanopsis glauca, and Alnus formosana

Trees in cities play a valuable public health role for they are able to use photosynthesis to absorb atmospheric carbon dioxide (CO2), which is then stored as tree biomass. The present study compared the potential for carbon storage in the aboveground tree biomass of 3-year-old specimens of Barringtonia racemosa, Cyclobalanopsis glauca, and Alnus formosana grown in Chiayi City, Taiwan. Assessment of the carbon storage of avenue trees was based on measurement of the photosynthetic rate and leaf area, as well as the biomass of timbers, from October 2008 to 2009. Based on photosynthetic rates and leaf area, the estimated carbon stocks of B. racemosa, C. glauca, and A. formosana are 756, 615, and 2738 kg Cha−1 a−1, respectively. In addition, carbon storage can be estimated based on timber volume, and these results are 1170, 720, and 1995 kg Cha−1 a−1 for B. racemosa, C. glauca, and A. formosana, respectively. Based on these findings, A. formosana has the highest carbon fixation potential of these three trees. Although the photosynthetic rate measurements can provide detailed data on the diurnal changes in carbon stocks, this requires more time and labor. In contrast, timber volume measurements provide a rapid and convenient way to estimate carbon stocks.

Avicennia germinans (black mangrove) vessel architecture is linked to chilling and salinity tolerance in the Gulf of Mexico.

Over the last several decades, the distribution of the black mangrove Avicennia germinans in the Gulf of Mexico has expanded, in part because it can survive the occasional freeze events and high soil salinities characteristic of the area. Vessel architecture may influence mangrove chilling and salinity tolerance. We surveyed populations of A. germinans throughout the Gulf to determine if vessel architecture was linked to field environmental conditions. We measured vessel density, hydraulically weighted vessel diameter, potential conductance capacity, and maximum tensile fracture stress. At each sampling site we recorded mangrove canopy height and soil salinity, and determined average minimum winter temperature from archived weather records. At a subset of sites, we measured carbon fixation rates using a LI-COR 6400XT Portable Photosynthesis System. Populations of A. germinans from cooler areas (Texas and Louisiana) had narrower vessels, likely reducing the risk of freeze-induced embolisms but also decreasing water conductance capacity. Vessels were also narrower in regions with high soil salinity, including Texas, USA and tidal flats in Veracruz, Mexico. Vessel density did not consistently vary with temperature or soil salinity. In abiotically stressful areas, A. germinans had a safe hydraulic architecture with narrower vessels that may increase local survival. This safe architecture appears to come at a substantial physiological cost in terms of reduction in conductance capacity and carbon fixation potential, likely contributing to lower canopy heights. The current distribution of A. germinans in the Gulf is influenced by the complex interplay between temperature, salinity, and vessel architecture. Given the plasticity of A. germinans vessel characters, it is likely that this mangrove species will be able to adapt to a wide range of potential future environmental conditions, and continue its expansion in the Gulf of Mexico in response to near-term climate change.

Theoretical Estimation of Algal Biomass Potential for Carbon Sequestration and Biofuel Production in Ethiopia

Five regions of Ethiopia were identified as potential sites for algal biomass cultivation considering both sunlight and local climatic conditions. The meteorological data, sunlight and air temperature information for the identified potential sites were used as a basis to estimate annual biomass production, lipid production and carbon sequestration potential. An average upper biomass, oil yield and carbon fixation potential was calculated to be 315 T/ha/yr, 111,202.4 L/ha/yr. and 89 T CO2 /ha/yr. This study provides a baseline data for theoretical estimates of open pond microalgae production systems in Ethiopia. This study will support the Ethiopian government in its Energy and Food Security policy to promote the use of indigenous and renewable sources for transportation fuels and income generation.