Carbon Supply Research Articles

Excessive use of chemical fertilizers in catchment areas raises the seasonal pH in natural freshwater lakes of the subtropical monsoon climate region

In recent years, the pH of some oligotrophic natural freshwater lakes in the subtropical monsoon climate region has generally reached an extremely high level of approximately 9.0 during the summer and autumn. It has not been proven that the explanation for why carbon assimilation in productive lakes exceeds carbon supply and causes a rise in pH also applies to oligotrophic freshwater lakes. Regardless, this may have been caused by changes in the solute composition of inflowing rivers as a result of changes in land use in catchment areas. Beimiao Reservoir in Baoshan City, Yunnan Province, where pH has increased significantly in summer and fall over the past few years, was chosen for this research in order to verify this hypothesis. This paper evaluates the status quo of water quality and nutrition in this reservoir. In addition, this paper analyzes the effects of water temperature, the metabolism of aquatic organisms, and river input on the horizontal and vertical spatial differences, diurnal variations, seasonal changes, and annual changes in the pH of the reservoir. It was discovered that one of the primary causes of the pH increase in natural freshwater lakes in the subtropical monsoon climate region during summer and autumn can be summarized as follows: A large amount of nitric acid and sulfuric acid are produced in the soil when chemical fertilizers are overused in runoff areas, particularly during intensive horticultural crop cultivation. Therefore, the subtropical monsoon climate region's soil loses calcium and magnesium ions, whose combined equivalent concentrations significantly exceed those of bicarbonate ions. The combined equivalent concentrations of calcium ions and magnesium ions in the inflowing rivers in summer and autumn are also significantly higher than those in the lake, resulting in the depletion of free carbon dioxide caused by calcium carbonate precipitation and an increase in pH. The conclusion of this research casts new light on the preservation and treatment of the ecological environment of lake water with similar issues.

Bio-decarbonization by microalgae: a comprehensive analysis of CO2 transport in photo-bioreactor

Microalgae biofilm is a typical porous structure where CO2 is converted by microalgae into organic matter. Therefore, CO2 transport and its distribution in porous biofilm are crucial for microalgae decarbonization and its energy utilization. In order to get detailed process information of CO2 transport and its bioconversion, a mathematical model considering the microalgae growth and its material consumptions was established for substances' flow and transport processes in an immersed microalgae biofilm reactor. Modeling results showed that CO2 concentration on the surface of biofilm reduced about 26.57% along the flow direction. Increased inlet CO2 concentration (0.2–5.2 ​mM) significantly promoted the average specific growth rate of biofilm, which was more dramatical at a low flow rate with an enhancement about 7.38 times. Essential reason for it is a synchronous increase on total transfer flux of CO2 (8.25 times by ϕ_CO2) and average CO2 consumption rate (7.48 times by ACR_CO2) in biofilm. However, such promotion gradually waned with a growing initial carbon supply concentration. Enhanced CO2 transport in biofilm caused by increasing culture medium's flow rate (1–6 ​mL ​min−1) doesn't always result in synchronous improvements on biofilm growth. At sufficient carbon supply, increased flow rate doesn't further effectively improve biofilm growth but greatly reduced CO2 removal. Whether increasing carbon supply concentration or flow rate, biofilm growth can't be significantly promoted unless the ϕ_CO2 and ACR_CO2 in biofilm were increased by almost the same level. This work provides a new and deeper mechanistic insight into macroscopic growth characteristics of biofilms from the perspective of CO2 transport in it, as well as providing some theoretical guidance towards the cultivation of immersed microalgae biofilm for bio-decarbonization.

Starch deficiency in tomato causes transcriptional reprogramming that modulates fruit development, metabolism and stress responses.

Tomato fruit (Solanum lycopersicum) store carbon as starch during early development and mobilize it at the onset of ripening. Starch accumulation has been suggested to buffer fluctuations in carbon supply to the fruit under abiotic stress, and contribute to sugar levels in ripe fruit. However, the role of starch accumulation and metabolism during fruit development is still unclear. Here we show that the tomato mutant adpressa (adp) harbors a mutation in a gene encoding the small subunit of ADP-glucose pyrophosphorylase (AGPase), which abolishes starch synthesis. The disruption of starch biosynthesis causes major transcriptional and metabolic remodeling in adp fruit but only minor effects on fruit size and ripening. Changes in gene expression and metabolite profiles indicate that the lack of carbon flow into starch increases levels of soluble sugars during fruit growth, triggers a readjustment of central carbohydrate and lipid metabolism, and activates growth and stress protection pathways. Accordingly, adp fruits are remarkably resistant to blossom-end rot, a common physiological disorder induced by environmental stress. Our results provide insights into the effects of perturbations of carbohydrate metabolism on tomato fruit development, with potential implications for the enhancement of protective mechanisms against abiotic stress in fleshy fruit.

New Estimate of the Supply of Dissolved Organic Carbon with Ob and Yenisei Water to the Kara Sea Basin

New Estimate of the Supply of Dissolved Organic Carbon with Ob and Yenisei Water to the Kara Sea Basin

Herbivore-driven disruption of arbuscular mycorrhizal carbon-for-nutrient exchange is ameliorated by neighboring plants

Arbuscular mycorrhizal fungi colonize the roots of most plants, forming a near-ubiquitous symbiosis1 that is typically characterized by the bi-directional exchange of fungal-acquired nutrients for plant-fixed carbon.2 Mycorrhizal fungi can form below-ground networks3,4,5,6 with potential to facilitate the movement of carbon, nutrients, and defense signals across plant communities.7,8,9 The importance of neighbors in mediating carbon-for-nutrient exchange between mycorrhizal fungi and their plant hosts remains equivocal, particularly when other competing pressures for plant resources are present. We manipulated carbon source and sink strengths of neighboring pairs of host plants through exposure to aphids and tracked the movement of carbon and nutrients through mycorrhizal fungal networks with isotope tracers. When carbon sink strengths of both neighboring plants were increased by aphid herbivory, plant carbon supply to extraradical mycorrhizal fungal hyphae was reduced, but mycorrhizal phosphorus supply to both plants was maintained, albeit variably, across treatments. However, when the sink strength of only one plant in a pair was increased, carbon supply to mycorrhizal fungi was restored. Our results show that loss of carbon inputs into mycorrhizal fungal hyphae from one plant may be ameliorated through inputs of a neighbor, demonstrating the responsiveness and resilience of mycorrhizal plant communities to biological stressors. Furthermore, our results indicate that mycorrhizal nutrient exchange dynamics are better understood as community-wide interactions between multiple players rather than as strict exchanges between individual plants and their symbionts, suggesting that mycorrhizal C-for-nutrient exchange is likely based more on unequal terms of trade than the "fair trade" model for symbiosis.

Walking the 'design-build-test-learn' cycle: flux analysis and genetic engineering reveal the pliability of plant central metabolism.

This article is a Commentary on Morley et al. (2023), 239: 1834–1851.

GmMFT: a potential step forward in soybean breeding for high oil and yield.

This article is a Commentary on Cai et al. (2023), 239: 905–919.

Therapeutic Potential of HMF and Its Derivatives: a Computational Study.

Over the past century, chemicals and energy have increasingly been derived from non-renewable resources. The growing demand for essential chemicals and shrinking inventory make reliable, sustainable sources essential. Carbohydrates offer by far the greatest carbon supply. Furan compounds, a particular family of dehydration products, are believed to offer high chemical potential. Here, we analyze 5-HMF (5, hydroxymethylfurfural) and some of its derivatives in particular, a furan-type platform chemical. To analyze the therapeutic potential of HMF and its derivatives, this study utilized cutting-edge technologies such as computer-aided drug design, virtual screening, molecular docking, and molecular dynamic simulation. We conducted 189 docking simulations and examined some of the most promising dock poses using the molecular dynamic simulator. As for the receptors for our compounds, the leading candidates are human acetylcholinesterase, beta-lactamases, P. aeruginosa LasR, and S. aureus tyrosyl-tRNA synthetases. Out of all derivatives considered in this study, 2,5-furandicarboxylic acid (FCA) performed best.

Pilot-scale Evaluation of an Anaerobic/Anoxic/Oxic Process for Nitrogen Removal from Sewage Using Metagenomic Sequencing

A modified pilot plant with two sequencing batch reactors on the strength of utilizing the inner carbon supply and adding suspended carriers was operated for 280 d to analyze nitrogen removal performance and microorganism community. Despite a low chemical oxygen demand (COD)/total nitrogen (TN) ratio of 3.5, the TN in the effluent decreased from 37.2 to 10.4 mg N/L. High-throughput sequencing indicated significant differences in the abundance of the phylum Actinobacteria (p<0.0001), Firmicutes (p<0.0001), Bacteroidetes (p<0.001), Uroviricota (p<0.0001) and Planctomycetes (p<0.0001) between the anoxic-carrier biofilms and flocculent sludge. Quantitative PCR revealed that denitrification and anammox genes were additional abundant in the anoxic-carrier biofilms than flocculent sludge (narG: p<0.0001; nirS: p<0.01; narH: p<0.01; norB: p<0.0001; hzsB: p<0.01; hdh: p<0.01). Thus, enrichment with denitrification and anammox bacteria might improve nitrogen removal; this was supported by KEGG pathway annotation. Collectively, this study suggests that anoxic-carrier biofilms might enhance nitrogen removal through partial denitrification and anammox process in CWWTPs.

Green hydrogen is a necessary component of a grid with an increasing non-dispatchable renewable energy supply

It is very well-known that wind and solar energy are supplied when there are resources, which are continuously changing, and not when demanded by the grid. Thus, in a grid without the supply of dispatchable electricity burning carbon and hydrocarbon combustion fuels, it is indispensable to include very large energy storage and given the variability not only short term within the day but from day to day following seasonality additional to weather, the large energy storage has to be mostly hydrogen. Extremely misleading are the cost assessment of prices of electricity to consumers through a Levelized Cost of Energy (LCOE) without factoring in dispatchability, as dispatchable and non-dispatchable electricity has a different value. Without energy storage, the production by wind and solar in the defect of the grid demand has to be supplied by other energy sources. Similarly, the production in excess would be wasted. This inconvenient truth has already produced increasing prices of electricity for customers. The Australian National Electricity Market data shows as phased with the uptake of wind and solar, in the absence of adequate energy storage, the price of energy supply has grown enormously. Without addressing the energy storage issue, mission net zero is incompatible with having cheap and abundant electricity.

Phosphorus-induced greater enhancement in carbon supply and storage for oil synthesis during the crucial period made cottonseed kernel oil yield have a higher increment than protein

Cottonseed has a high utilization value due to its luxuriant oil and protein, but low phosphorus (P) in cropland reduces its yield and quality. A limited understanding of the physiological mechanism underlying these results restricted the exploration of P efficient management in cotton cultivation. A 3-year experiment was performed with Lu 54 (low-P sensitive) and Yuzaomian 9110 (low-P tolerant) under 0 (deficient-P), 100 (critical-P), and 200 (excessive-P) kg P2O5 ha−1 in a field having 16.9 mg kg−1 available P to explore the key pathway for P to regulate cottonseed oil and protein formation. P application markedly increased cottonseed oil and protein yields, with the enhanced acetyl-CoA and oxaloacetate contents during 20–26 days post anthesis being a vital reason. Notably, during the crucial period, decreased phosphoenolpyruvate carboxylase activity weakened the carbon allocation to protein, making malonyl-CoA content increase greater than free amino acid; Meanwhile, P application accelerated the carbon storage in oil but retarded that in protein. Consequently, cottonseed oil yield increased more than protein. Oil and protein synthesis in Lu 54 was more susceptible to P, resulting in greater increments in oil and protein yields than Yuzaomian 9110. Based on acetyl-CoA and oxaloacetate contents (the key substrates), the critical P content in the subtending leaf to cotton boll needed by oil and protein synthesis in Lu 54 (0.35%) was higher than Yuzaomian 9110 (0.31%). This study provided a new perception of the regulation of P on cottonseed oil and protein formation, contributing to the efficient P management in cotton cultivation.

Widening the landscape of transcriptional regulation of green algal photoprotection

Availability of light and CO2, substrates of microalgae photosynthesis, is frequently far from optimal. Microalgae activate photoprotection under strong light, to prevent oxidative damage, and the CO2 Concentrating Mechanism (CCM) under low CO2, to raise intracellular CO2 levels. The two processes are interconnected; yet, the underlying transcriptional regulators remain largely unknown. Employing a large transcriptomic data compendium of Chlamydomonas reinhardtii’s responses to different light and carbon supply, we reconstruct a consensus genome-scale gene regulatory network from complementary inference approaches and use it to elucidate transcriptional regulators of photoprotection. We show that the CCM regulator LCR1 also controls photoprotection, and that QER7, a Squamosa Binding Protein, suppresses photoprotection- and CCM-gene expression under the control of the blue light photoreceptor Phototropin. By demonstrating the existence of regulatory hubs that channel light- and CO2-mediated signals into a common response, our study provides an accessible resource to dissect gene expression regulation in this microalga.

Verifying the applicability of PD/A unit for ultimate sidestream and mainstream polishing: Operating performance, granular characteristics and active microbes

Partial denitrification/anammox (PD/A) has been recently applied to co-treat domestic wastewater and nitrate-containing anammox effluent. However, studies regarding its performance without external organic supplement, spatial characteristics within sludge aggregates, and chronological changes of active microorganisms along PD/A cycle have rarely been reported. Herein, one-stage PD/A unit extremely and simultaneously polished anammox-pretreated reject water (NH4+-N: 65.4 ± 5.7 mg/L, COD: 199.7 ± 23.2 mg/L) and domestic wastewater (NO3−-N: 81.6 ± 7.8 mg/L, TN: 85.8 ± 8.9 mg/L, COD: 338.2 ± 29.0 mg/L) to 4.5 ± 2.1 mg/L without external organic carbon supply. Protective “granules-in-granule” aggregates with densely clustered anammox bacteria embedded in homogeneous denitrifying Thauera prevailed in PD/A system, surviving disadvantages from complex wastewater. Uronic acids and β-sheet proteins in outer extracellular matrix facilitated granulation and pollutants adsorption, while tryptophan- and aromatic-like proteins with tighter secondary structure in inner extracellular matrix maintained granular robustness. Importantly, succession of active microorganisms along the PD/A cycle was revealed by transcript-level analysis for the first time. In PD-period, stimulated Thauera contributed to rapid nitrite accumulation. In subsequent anammox-period, Ca.Brocadia was activated to conduct advanced nitrogen removal, which accompanied the timely nitrate-to-nitrite reduction by Thauera and Ca.Competibacter. Elusimicrobia was active throughout the PD/A cycle, which is conducive to eliminate the dependence of PD process on external carbon source by decomposing complex organics in actual wastewater. Protective granular structure, orderly activation and harmonious cooperation of functional consortia facilitated practical nitrogen removal rate of 0.6 ± 0.1 kg-N/m3/d under anoxic condition, which sheds light on engineering application of anammox technology.

New Estimate of the Supply of Dissolved Organic Carbon with the Waters of the Ob and Yenisei to the Kara Sea Basin

Calculations were made of the runoff of dissolved organic carbon (DOC) into the Kara Sea with the waters of the Ob and Yenisei rivers. The estimates performed showed that the DOC runoff with the Yenisei waters (3.67 × 106 tC/year) is less than the DOC runoff with the Ob waters (4.06 × 106 tC/year), which is due to differences in the structure of the drainage basins and estuaries of these rivers. All previous published estimates show the opposite. The lack of the DOC content data during the maximum flood of the Yenisei does not let us calculate accurately the DOC runoff with its waters, but makes it possible to estimate its maximum and minimum values (3.11–4.18 × 106 tC/year).

Pacific Water impacts the burial of black and total organic carbon on the Chukchi Sea shelf, Arctic Ocean

The Arctic shelf is an important carbon reservoir, especially the Chukchi Sea, which plays a vital role in the biogeochemical processes of polar carbon cycles. In this study, we measured the contents of black carbon (BC) and total organic carbon (TOC) in a sediment core of the Chukchi Sea shelf, to evaluate the controlling factors of distribution and burial of BC and TOC. Our results show that the distribution of TOC and BC was strongly influenced by the Pacific Water (PW) inflow, resulting in nearly synchronous change since the early Holocene. The early Holocene (∼9.9 to 8.0 cal kyr BP) was characterized by the minimum of TOC, total nitrogen (TN), and BC, and the most depleted δ13CTOC and δ13CBC values throughout the Holocene, which indicate low primary productivity and low BC supplies under the weak PW flux. The carbon (TOC and BC) burial on the Chukchi Sea shelf was significantly enhanced during the middle Holocene (8.0–4.0 cal kyr BP) due to the rapid increase in PW flux. Since 4.0 cal kyr BP, PW inflow is stable and active, which enables sea ice extent to modulate the stratigraphic variations of BC. In particular, an increase in summer Arctic sea ice during this period may enhance ice-rafted debris and terrestrial carbon supply by promoting erosion of coastal peat soils and permafrost. Our results suggest that PW inflow is the first-order factor controlling Arctic carbon burial during the Holocene, while insolation-induced sea ice increase started playing a role when the PW inflow is active and stable during the late Holocene.

Soil fertility determines whether ectomycorrhizal fungi accelerate or decelerate decomposition in a temperate forest.

Ectomycorrhizal (ECM) fungi can both accelerate and decelerate decomposition of organic matter in forest soils, but a mechanistic understanding of this differential influence is limited. Here, we tested how ECM fungi affect decomposition along a natural fertility gradient in a temperate forest of European beech. Trees were girdled to reduce belowground carbon supply to the soil. Girdling shifted soil fungal community composition and decreased hyphal biomass production and soil CO2 efflux, indicating a reduced ECM fungal activity. Girdling also affected decomposition processes, but the effects depended on fertility. Our results indicate that ECM fungi decelerate decomposition under conditions of low fertility while under conditions of high fertility ECM fungi and their host roots have an accelerating effect. We conclude that both acceleration and deceleration of decomposition of organic matter by ECM fungi can occur within a forest, with soil fertility determining the direction and magnitude of these effects. We suggest a positive feedback between fertility, stand productivity and soil carbon and nitrogen dynamics that is mediated to a large extent by ECM fungi.

No carbon storage in growth-limited trees in a semi-arid woodland

Plant survival depends on a balance between carbon supply and demand. When carbon supply becomes limited, plants buffer demand by using stored carbohydrates (sugar and starch). During drought, NSCs (non-structural carbohydrates) may accumulate if growth stops before photosynthesis. This expectation is pervasive, yet few studies have combined simultaneous measurements of drought, photosynthesis, growth, and carbon storage to test this. Using a field experiment with mature trees in a semi-arid woodland, we show that growth and photosynthesis slow in parallel as {psi }_{{pd}} declines, preventing carbon storage in two species of conifer (J. monosperma and P. edulis). During experimental drought, growth and photosynthesis were frequently co-limited. Our results point to an alternative perspective on how plants use carbon that views growth and photosynthesis as independent processes both regulated by water availability.

Carbon supplementation in domestic sewage via mixing with paint booth effluent: Influence on the performance of bioremediation and algal biomass production from high-rate algal ponds

The paint booth effluent (PBE) was used as a carbon supplement to evaluate the treatment of domestic sewage (DS) via microalgae biotechnology. The present study aimed to assess the performance of different mixtures of PBE and DS in the treatment and production of algal biomass in high-rate algal ponds (HRAPs), seeking to determine the optimal mixture between the effluents. The blends were: D1 (0% PBE, 100 % DS), D2 (18.75 % PBE, 81.25 % DS), D3 (37.5 % PBE, 62.5 % DS), D4 (56.25 % PBE, 43.75 % DS) and D5 (75% PBE, 25 % DS). As a result, in the D2 blend, with better carbon, nitrogen, and phosphorus ratio, there was a higher primary and total biomass productivity (0.08 g chl-α/m2.day and 2.0 g VSS/m2.day). The regression adjustment corroborated the results of the D2 mixture, showing PBE dosages between 18 and 25 % as better for algal growth. The insertion of PBE in the medium positively affected the bioremediation performance, increasing the removals with the addition of PBE. The nutrient and organic matter removal efficiencies ranged from values close to 50 %, of total organic carbon in the D1 mixture, and reaching 100 % in the removal of ammoniacal nitrogen. The D2 mixture stands out with the highest nitrogen recovery via the assimilation of organic nitrogen, reaching 19 % more in relation to the initial value. Thus, PBE contributed to the supply of organic carbon to the biomass, favoring the consortium between algae and bacteria.

Carbon Sink Limitation Determines the Formation of the Altitudinal Upper Limit of an Evergreen Oak in Eastern China

Temperature is a critical environmental factor determining the upper limits of evergreen broadleaved tree taxa. However, whether carbon source or carbon sink limitation shapes this limit is not yet fully understood. We studied a subtropical evergreen oak (Cyclobalanopsis gracilis) at the northern limit of its distributional range. Along an elevational/temperature gradient towards its upper limit, we surveyed the variations in non-structural carbohydrate (NSC) concentrations of C. gracilis adults for 3 years. Additionally, a carbon balance manipulation experiment of debudding and defoliation was done to C. gracilis seedlings close to the upper distributional limit, aiming at investigating the changes in NSC concentrations and growth rates in different treatment groups. Our results showed that increasing elevation or decreasing temperature did not affect the trends of NSC concentration in twigs, old branches, or trunks of adults, nor did carbon balance manipulations (debudding or defoliation) of seedlings have a significant effect on the growth, while defoliation decreased NSC concentration in twigs. These results suggest that carbon sink limitation is the key physiological mechanism underlying low temperature in the shaping of this dominant evergreen broadleaved tree species in eastern China. Therefore, the formation of upper limits in evergreen oaks is most likely the result of a direct low-temperature restriction on meristematic activity and tissue formation instead of the result of insufficient carbon supply. More studies with expanded sample sizes are needed on other evergreen broadleaved tree species growing at their upper limits to confirm the carbon sink limitation hypothesis and reveal the detailed mechanisms.

Regulation of marine plankton respiration: A test of models

Plankton respiration is a major process removing oxygen from pelagic environments and constitutes one of the largest oxygen transformations in the sea. Where the O2 supplies due to dissolution, advection and oxygenic photosynthesis are not sufficient, hypoxic, or anoxic waters may result. Coastal waters with limited water exchange are especially prone to have low oxygen levels due to eutrophication and climate change. To support marine environmental management in a period of rapid climate change, we investigated the current knowledge of regulating plankton respiration based on field and experimental studies reported in the literature. Models for regulation of plankton respiration was tested on a three-year field data set. Temperature is the most reported predictor positively influencing plankton respiration (mean r2 = 0.50, n=15). The organic carbon supply driven by primary production has a similar coefficient of determination but fewer reported relationships (mean r2 = 0.52, n=6). Riverine discharges of dissolved organic carbon can override the influence of primary production in estuaries precluding effects of nutrient reductions. The median predictions of respiration regulation produced by current models vary by a factor of 2 from the median of observed values and extreme values varied even more. Predictions by models are therefore still too uncertain for application at regional and local scales. Models with temperature as predictor showed best performance but deviated from measured values in some seasons. The combined dependence of plankton respiration on temperature, phytoplankton production and discharge of riverine organic carbon will probably lead to increased oxygen consumption and reduced oxygen levels with projected climate change. This will be especially pronounced where increased precipitation is expected to enhance riverine discharges of carbon compounds. The biologically mediated transfer of carbon for long-term storage in deeper layers will slow down. Implementation of plankton respiration measurements in long-term ecological monitoring programs at water body and basin scales is advocated, which would enable future multivariate analyses and improvements in model precision across aquatic environments.