Biogeochemical Cycles Research Articles

Combined Quantification and Characterization of Dissolved Organic Matter by Liquid Chromatography-Mass Spectrometry Using Charged Aerosol Detection.

Dissolved organic matter (DOM) is a complex mixture of thousands of molecular formulas comprised of an unknown number of chemical compounds, the concentration and composition of which are critical to ecosystem function and biogeochemical cycling. Despite its importance, our understanding of the DOM composition is lacking. This is principally due to its molecular complexity, which means that no single method is capable of describing DOM in its entirety. Quantification is typically done by proxy (e.g., relative to carbon content) and does not necessarily match well to compositional data, due to incomplete analytical windows and selectivity of different analytical methods. We present an integrated liquid chromatography (LC)-diode array detector (DAD)-charged aerosol detector (CAD)-mass spectrometry (MS) pipeline designed to both characterize and quantify solid-phase extractable DOM (SPE-DOM) in a single analysis. We applied this method to a set of eight Swedish water bodies sampled in the summer and winter. Chromophoric SPE-DOM was proportionally higher in samples with higher SPE-DOM concentrations but remained relatively consistent between sampling occasions. Ionizable SPE-DOM was relatively consistent across sites but was proportionally higher in summer. Overall, the carbon content of DOM was very consistently ∼40% across sites in both summer and winter. These findings suggest that SPE-DOM concentration at these sites is driven by (presumably allochthonous) chromophoric inputs, with an increased relative contribution in summer of material that is more ionizable and less chromophoric and may be either autochthonous or selectively enriched from allochthonous sources. Thus, with minimal additional effort, this method provided further compositional insights not attained by any single analysis in isolation.

An integrated fast-slow plant and nematode economics spectrum predicts soil organic carbon dynamics during natural restoration.

Aboveground and belowground attributes of terrestrial ecosystems interact to shape carbon (C) cycling. However, plants and soil organisms are usually studied separately, leading to a knowledge gap regarding their coordinated contributions to ecosystem C cycling. We explored whether integrated consideration of plant and nematode traits better explained soil organic C (SOC) dynamics than plant or nematode traits considered separately. Our study system was a space-for-time natural restoration chronosequence following agricultural abandonment in a subtropical region, with pioneer, early, mid and climax stages. We identified an integrated fast-slow trait spectrum encompassing plants and nematodes, demonstrating coordinated shifts from fast strategies in the pioneer stage to slow strategies in the climax stage, corresponding to enhanced SOC dynamics. Joint consideration of plant and nematode traits explained more variation in SOC than by either group alone. Structural equation modeling revealed that the integrated fast-slow trait spectrum influenced SOC through its regulation of microbial traits, including microbial C use efficiency and microbial biomass. Our findings confirm the pivotal role of plant-nematode trait coordination in modulating ecosystem C cycling and highlight the value of incorporating belowground traits into biogeochemical cycling under global change scenarios.

Rapid response of stream dissolved phosphorus concentrations to wildfire smoke

Wildfires can produce large plumes of smoke that are transported across vast distances, altering nutrient cycling of undisturbed watersheds exposed downwind. To date, wildfire smoke influence on stream biogeochemical signatures remains an important knowledge gap. Here we evaluate the impacts of wildfire smoke on phosphorus (P) biogeochemical cycling in a temperate watershed in the Finger Lakes Region of Central New York located downwind from record setting Canadian forest fires during the summer of 2023. Daily sampling of stream and rainwaters was conducted over the 2 month smoke period, generating a robust geochemical dataset. Stream dissolved P showed high sensitivity to smoke events, attaining concentrations 2–3 × greater than the pre-smoke period. Subsequent rain events after smoke deposition were identified as a potentially important factor in magnitude and timing of dissolved P responses. These findings demonstrate the capacity for wildfire smoke to trigger rapid, observable changes to stream P chemistry.

Biodiversity of mudflat intertidal viromes along the Chinese coasts

Viruses constitute the most diverse and abundant biological entities on Earth. However, our understanding of this tiniest life form in complex ecosystems remains limited. Here, we recover 20,102 viral OTUs from twelve intertidal zones along the Chinese coasts. Our analysis demonstrates high viral diversity and functional potential in intertidal zones, encoding important functional genes that can be potentially transferred to microbial hosts and mediate elemental biogeochemical cycles, especially carbon, phosphate and sulfur. Virus-host abundance dynamics vary among different microbial lineages. Viral community composition is closely associated with environmental conditions, including dissolved organic matter. Concordant biogeographic patterns are observed for viruses and microbes. Viral communities are generally habitat specific with low overlaps between intertidal and other habitats. Environmental factors and geographic distance dominate the compositional variation of intertidal viromes. Overall, these findings expand our understanding of intertidal viromes within an ecological framework, providing insights into the virus-host coevolutionary arms race.

Wild pigs influence tropical forest soil microbial communities in a forest-agriculture mosaic landscape

Edge effects, the altered abiotic and biotic conditions on the borders of natural areas, have rarely been linked to altered soil biota, which shape ecosystem processes including carbon storage, biogeochemical cycling, and plant performance. Here, we investigated if increased wildlife populations (their increase mediated by foraging in nearby oil palm plantations) affect soil biota when they move between plantations and natural habitats. We used a 22-year fenced exclusion experiment in a primary rain forest in Peninsular Malaysia. We found that the presence of wildlife (mainly native pigs; Sus scrofa) was associated with greater bacterial diversity, an altered bacterial community composition, and indications of a reduced abundance of symbiotic ectomycorrhizal fungi. There were only minor effects of pigs on soil chemistry or microclimate, so we suggest that changes in soil communities are driven by pigs’ leaf litter removal and alterations to plant composition. Our study highlights that indirect effects from agriculture can be induced by wildlife more than1 km into protected areas and this could have important repercussions for ecosystem processes and plant-soil feedbacks.

Adaptive traits of Nitrosocosmicus clade ammonia-oxidizing archaea.

Nitrification is a vital process within the global biogeochemical nitrogen cycle but plays a significant role in the eutrophication of aquatic ecosystems and the production of the greenhouse gas nitrous oxide (N2O) from industrial agriculture ecosystems. While various types of ammonia-oxidizing microorganisms play a critical role in the N cycle, ammonia-oxidizing archaea (AOA) are often the most abundant nitrifiers in natural environments. Members of the genus Nitrosocosmicus are one of the prevalent AOA groups detected in undisturbed terrestrial ecosystems and have previously been reported to possess a range of physiological characteristics that set their physiology apart from other AOA species. This study provides significant progress in understanding these unique physiological traits and their genetic drivers. Our results highlight how physiological studies based on comparative genomics-driven hypotheses can contribute to understanding the unique niche of Nitrosocosmicus AOA.

Hypoxia extreme events in a changing climate: Machine learning methods and deterministic simulations for future scenarios development in the Venice Lagoon

Climate change pressures include the dissolved oxygen decline that in lagoon ecosystems can lead to hypoxia, i.e. low dissolved oxygen concentrations, which have consequences to ecosystem functioning including biogeochemical cycling from mild to severe disruption. The study investigates the potential of machine learning (ML) and deterministic models to predict future hypoxia events. Employing ML models, e.g. Random Forest and AdaBoost, past hypoxia events (2008–2019) in the Venice Lagoon were classified with an F1 score of around 0.83, based on water quality, meteorological, and spatio-temporal factors. Future scenarios (2050, 2100) were estimated by integrating hydrodynamic-biogeochemical and climate projections. Results suggest hypoxia events will increase from 3.5 % to 8.8 % by 2100, particularly in landward lagoon areas. Summer prediction foresee a rise from 118 events to 265 by 2100, with a longer hypoxia-prone season. This model is a valuable tool for developing hypoxia scenarios, aiding in identifying restoration hotspots for climate-threatened lagoons.

Biogeographic shifts in the microbial co-occurrence network features of three domains across complex environmental gradients in subtropical coastal waters

BackgroundBacteria, Archaea, and Microeukaryotes comprise taxonomic domains that interact in mediating biogeochemical cycles in coastal waters. Many studies have revealed contrasting biogeographic patterns of community structure and assembly mechanisms in microbial communities from different domains in coastal ecosystems; however, knowledge of specific biogeographic patterns on microbial co-occurrence relationships across complex coastal environmental gradients remains limited. Using a dense sampling scheme at the regional scale, SSU rRNA gene amplicon sequencing, and network analysis, we investigated intra- and inter-domain co-occurrence relationships and network topology-based biogeographic patterns from three microbial domains in coastal waters that show environmental gradients across the inshore-nearshore-offshore continuum in the East China Sea.ResultsOverall, we found the highest complexity and connectivity in the bacterial network, the highest modularity in the archaeal network, and the lowest complexity, connectivity, and modularity in the microeukaryotic network. Although microbial co-occurrence networks from the three domains showed distinct topological features, they exhibited a consistent biogeographic pattern across the inshore-nearshore-offshore continuum. Specifically, the nearshore zones with intermediate levels of terrestrial impacts reflected by multiple environmental factors (including water temperature, salinity, pH, dissolved oxygen, and nutrient-related parameters) had a higher intensity of microbial co-occurrence for all three domains. In contrast, the intensity of microbial co-occurrence was weaker in both the inshore and the offshore zones at the two ends of the environmental gradients. Archaea occupied a central position in the microbial inter-domain co-occurrence network. In particular, members of the Thaumarchaeota Marine Group I (MGI, now placed within the Family Nitrosopumilaceae of the Phylum Thermoproteota) appeared to be the hubs in the biogeographic shift between inter-domain network modules across environmental gradients.ConclusionsOur work offers new insights into microbial biogeography by integrating network features into biogeographic patterns, towards a better understanding of the potential of microbial interactions in shaping biogeographic patterns of coastal marine microbiota.

Carbon Cycling in Marine Particles Based on Inorganic and Organic Stable Isotopes

The marine carbon cycle has a central role in biogeochemical cycling and a close interaction with the climate system. Here, we use the stable carbon isotope (δ13C) of particulate inorganic carbon (PIC) and particulate organic carbon (POC) in marine particles to diagnose carbonate dissolution and organic matter respiration processes in the ocean water column. We show PIC dissolution both in the euphotic zone, potentially driven by POC remineralization, and a preferential dissolution of coccoliths compared to foraminifera below the saturation horizon in the water column. Within the oxygen deficient zone (ODZ), POC remineralization and consequent respiration-driven PIC dissolution are both significantly diminished. We also demonstrate that POC remineralization preferentially removes a 13C-enriched component compared to isotopically-light bulk POC in both the large size fraction (LSF, > 51μ m) and small size fraction (SSF, 0.5 – 51μ m) of the pump particles, but exhibits a greater impact on the large particles because of its smaller inventory. Simultaneously, addition of a 13C-enriched heterotrophic or chemoautotrophic component to the SSF further increases the isotopic offset between SSF and LSF POC. Overall, this study uses δ13C to provide novel evidence for different biogeochemical processes in marine particles, and demonstrates carbonate dissolution in the ocean water column, both driven by bulk seawater chemistry and organic matter respiration within particles. The absence of O2 in the ODZ likely protects carbonate from dissolving by severely limiting organic matter respiration, thus reducing shallow PIC dissolution within the ODZs.

Morphology and molecular phylogeny of Pelagothrix abietum (Penard, 1922) comb. nov. and two new Metacystis and Apolagynus species (Ciliophora, Prostomatea)

Ciliates of the class Prostomatea show a broad spectrum of feeding strategies and often occur abundantly in various aquatic habitats, playing a vital role in the biogeochemical cycle. Due to their small cell size and simple structure, prostomateans were considered to be a group with a lower degree of morphological differentiation for a long time. However, recent research suggests that the diversity of this group of ciliates is higher than previously thought. In the present study, three prostomateans, collected from different localities in China and classified into three families, were examined using morphological and phylogenetic techniques. Our analyses revealed two new species, Metacystis multitricha sp. nov. and Apolagynus spiralis sp. nov., and suggested a transfer of Prorodon abietum Penard, 1922 to the genus Pelagothrix. Phylogenetic analyses corroborated the morphological classifications of the three species into the families Metacystidae, Lagynusidae, and Holophryidae, respectively, demonstrating that their diagnostic characteristics bear an evolutionary signal at the family level.

Midseason draining of paddy water suppresses microbial arsenic methylation in soil and alleviates rice straighthead disease

Arsenic (As) methylation is an important component of As biogeochemical cycle. Microbial As methylation is enhanced under anoxic conditions in paddy soil, producing dimethylarsenate (DMA) which can cause physiological straighthead disease in rice. We conducted field experiments at two sites to test the effect of midseason draining of paddy water on microbial As methylation and the incidence of straighthead disease. Compared to continuous flooding, midseason draining increased soil Eh, decreased the abundances of microbial genes for arsenate reduction (arsC and arrA) and arsenite methylation (arsM), and lowered the concentrations of both inorganic As and DMA in soil porewater. Draining shifted microbial composition, resulting in decreases in the relative abundance of 17–132 amplicon sequence variants. Draining decreased the accumulation of DMA in rice husk and of inorganic As and DMA in rice grain, decreased the incidence of straighthead disease, and increased grain yield by 20–45 %. Further experiments were conducted at eight field sites to assess the effect of midseason draining in a split field design. Draining decreased husk DMA concentration by 40–65 % and increased grain yield by 25–209 %. This study demonstrates that midseason draining can effectively suppress microbial As methylation and alleviate rice straighthead disease, benefiting both grain yield and safety.

Impact of warming and acidification of the Mediterranean Sea on statolith formation of the scyphozoan jellyfish Rhizostoma pulmo Macri (1778)

Ocean warming and acidification negatively affect organisms and biogeochemical cycles. To date, emphasis has been placed on the study of the impact on the structures of calcifying species; however, there is limited knowledge about the influence of the increase of these two variables on the solid structures of non-calcifying species as jellyfish. Here, we study the effects that the increase of temperature and acidity would cause on the statoliths of newly released ephyrae of the Mediterranean jellyfish Rhizostoma pulmo. Six combinations of temperature and PCO2 (18, 24 and 30ºC with a PCO2 of 500 and 1000 ppm each), according to the projections of the SSP5-8.5 (IPCC, 2021) scenario for the year 2100, were applied during 32 days to different groups of polyps randomly selected. Statoliths of the released ephyrae were counted and their size was measured. Our results show that, even though neither temperature nor PCO2 increase exerted a representative effect on the amount of statoliths synthesized in newly released ephyra from R. pulmo, it did exert an impact on the size of these structures: warming led to the formation of larger statoliths, while the rise in PCO2 induced the production of smaller structures. Under the simultaneous increase of both variables, acidification attenuated the effects of temperature, but still slightly larger statoliths were synthesized. The size differences observed in these structures could negatively impact the equilibrium system of this jellyfish species, potentially affecting its ability to survive.

Deciphering the biodegradation of thiamethoxam by Phanerochaete chrysosporium with natural siderite: Synergistic mechanisms, transcriptomics characterization, and molecular simulation

Fungi play vital roles in the fate of organic pollutants, particularly when interacting with minerals in aquatic and soil environments. Mechanisms by which fungi may mitigate pollutions in fungus-mineral interactions are still unclear. Inspired by biogeochemical cycling, we constructed a range of co-culture systems to investigate synergistic effects of the white-rot fungus Phanerochaete chrysosporium and the iron-bearing mineral siderite on thiamethoxam (THX) transformation, a common neonicotinoid pesticide. Co-culturing with siderite significantly enhanced THX transformation during the initial 10 days with a dose effect, achieving 86 % removal within 25 days. Fungi could affect siderite’s dissolution, transformation, and precipitation through their biological activities. These interactions triggered physiological adaptation and resilience in fungi. Siderite could enhance the activity of fungal ligninolytic enzymes and cytochrome P450, facilitating biotransformation. Genes expression related to growth, energy metabolism, and oxidative stress response upregulated, enhancing fungal resilience to THX. The primary THX degradation pathways included nitro-reduction, C-N cleavage, and de-chlorination. Molecular dynamics simulations provided insights into catalytic mechanisms of enzyme-THX interactions. Together, siderite could act as natural enhancers that endowed fungi to resist physical and chemical stresses in environments, providing insights into contaminants attenuation, fungal biomineralization, and the coevolution of the Earth's lithosphere and biosphere.

Unveiling the potential role of virus-encoded polyphosphate kinases in enhancing phosphorus removal in activated sludge systems

While microbial phosphate removal in activated sludge (AS) systems has been extensively studied, the role of viruses in this process remains largely unexplored. In this study, we identified 149 viral auxiliary metabolic genes associated with phosphorus cycling from 2,510 viral contigs (VCs) derived from AS systems. Notably, polyphosphate kinase 1 (ppk1) and polyphosphate kinase 2 (ppk2) genes, which are primarily responsible for phosphate removal, were found in five unclassified VCs. These genes exhibited conserved protein structures and active catalytic sites, indicating a pivotal role of viruses in enhancing phosphorus removal. Phylogenetic analysis demonstrated a close relationship between viral ppk genes and their bacterial counterparts, suggesting the occurrence of horizontal gene transfer. Furthermore, experimental assays validated that viral ppk genes enhanced host phosphate removal capabilities. VCs carrying ppk genes were observed across diverse ecological and geographical contexts, suggesting their potential to bolster host functions in varied environmental and nutrient settings, spanning natural and engineered systems. These findings uncover a previously underappreciated mechanism by which viruses enhance phosphate removal in wastewater treatment plants. Overall, our study highlights the potential for leveraging virus-encoded genes to improve the efficiency of biological phosphorus removal processes, offering new insights into the microbial ecology of AS systems and the role of viruses in biogeochemical cycling.

An ultra-sensitive bimetallic based electrochemical sensor for analysis of total iron, total dissolved iron, and granular iron in coastal water

Different iron species play crucial roles in the biogeochemical cycle, so their determination is important. Electrochemical methods are among the most promising and easiest methods for the rapid on-site determination of different iron species. In this study, a new electrode—Au–Bi/ITO—based on the commercial indium tin oxide (ITO) electrode was etched and functionalized with bismuth nanoparticles (BiNPs) and gold nanoparticles (AuNPs) nanocomposites for voltammetric analysis of iron species in coastal water. After etching, the ITO electrode exhibits a higher number of attachment sites for the nanomaterials, thereby improving the stability of the resulting electrode, and the introduction of the nanomaterials improves the sensitivity of the electrode, making it easier to realize on-site detection. Under the synergistic effect of the two nanomaterials, the Au-Bi/ITO electrode showed excellent performance for the determination of different iron species in coastal water. Under the optimal conditions, the Au-Bi/ITO electrode peak current was linear in the concentration range from 5 nM to 1.5 μM with an ultralow detection limit of 1.4 nM. The results are consistent with certified values when the electrode is used for the determination of Fe(III) in certified reference materials. In summary, the Au-Bi/ITO electrode, with its high stability and sensitivity, has been successfully used for the direct determination of different Fe(III) species in coastal water via cathodic stripping voltammetry. This electrode is simple to prepare, easy to use, economical, and highly promising for future applications involving the rapid on-site detection of different iron species.

A critical assessment of geological weighing lysimeters: Part 2—Modelling field scale soil moisture storage and hydrological fluxes

AbstractLand surface models (LSMs) are used to simulate the terrestrial component of water, energy, and biogeochemical cycles. These simulations are useful for water resources management, drought and flood prediction, and numerical climate/weather prediction. However, the usefulness of LSMs are dependent by their ability to reproduce states and fluxes realistically. Accurate measurements of water storage are useful to calibrate and validate LSMs outputs. Geological weighing lysimeters (GWLs) are instruments that can provide field‐scale estimates of integrated total water storage within a soil profile. We use field estimates of total water storage and subsurface storage to critically evaluate two different land surface models: the Modélisation Environnementale communautaire—Surface Hydrology (MESH) which uses the Canadian Land Surface Scheme (CLASS), and the Structure for Unifying Multiple Modeling Alternatives: (SUMMA). These models have differences in how the processes and properties of the land surface are represented. We attempted to parameterize each model in an equivalent manner, to minimize model differences. Both models were able to reproduce observations of total water storage and subsurface storage reasonably well. However, there were inconsistencies in the simulated timing of snowmelt; depth of soil freezing; total evapotranspiration; partitioning of evaporation between soil evaporation and evaporation of intercepted water; and soil drainage. No one model emerged as better overall, though each model had specific strengths and weaknesses that we describe. Insights from this study can be used to improve model physics and performance.

Deciphering the impact of cascade reservoirs on nitrogen transport and nitrate transformation: Insights from multiple isotope analysis and machine learning

Construction of cascade reservoirs has altered nutrient dynamics and biogeochemical cycles, thereby influencing the composition and productivity of river ecosystems. The Lancang River (LCR), characterized by its cascade reservoir system, presents uncertainties in nitrogen transport and nitrate transformation mechanisms. Herein, we conducted monthly monitoring of hydrochemistry and multiple stable isotopes (δ15N-NO3-, δ18O-NO3-, δ18O-H2O, δD-H2O) throughout 2019 in both the natural river reach (NRR) and cascade reservoirs reach (CRR) of the LCR. Through the monthly detection of nitrogen forms and runoff in the import (M2) and export (M9) section, the average annual retention ratios for Total nitrogen (TN), Nitrate nitrogen (NO3--N), Particulate Nitrogen (PN) and Ammonium Nitrogen (NH4+-N) were about -35%, -53%, 48% and -65%, respectively. The retention rates were positively correlated with hydraulic retention time and negatively correlated with reservoir age, especially in the flood season. Compared to the NRR, the reservoir had significantly affected the nitrogen transport characteristics, especially for the large reservoirs (like Xiaowan and Nuozhadu), which enhanced phytoplankton uptake of NO3--N to form PN capabilities in the lentic environment and subsequently to precipitate or intercept it at the reservoir. This led to the overall decreasing trend of TN and PN concentrations along the CRR. The Bayesian stable isotope model quantified NO3--N sources from the NRR to the CRR. During this transition, soil nitrogen (SN) ratios decreased from 69.3% to 61.8%, while Manure & sewage (M&S) increased from 24.0% to 31.3%. Anthropogenic and natural factors, including urban sewage discharge, population density, and precipitation, were selected as key predictor variables. The eXtreme Gradient Boosting (XGBoost) model exhibited superior predictive performance for NO3--N concentrations, achieving an R2 of 0.70. These findings deepen our understanding of the impact of reservoirs on river ecology.

Gross Primary Production of Antarctic Landfast Sea Ice: A Model‐Based Estimate

AbstractMuch of the Antarctic coast is covered by seasonal landfast sea ice (fast ice), which serves as an important habitat for ice algae. Fast‐ice algae provide a key early season food source for pelagic and benthic food webs, and contribute to biogeochemical cycling in Antarctic coastal ecosystems. Summertime fast ice is undergoing a decline, leading to more seasonal fast ice with unknown impacts on interconnected Earth system processes. Our understanding of the spatiotemporal variability of Antarctic fast ice, and its impact on polar ecosystems is currently limited. Evaluating the overall productivity of fast‐ice algae has historically been hampered by limitations in observations and models. By linking new fast‐ice extent maps with a one‐dimensional sea‐ice biogeochemical model, we provide the first estimate of the spatio‐seasonal variability of Antarctic fast‐ice algal gross primary production (GPP) and its annual primary production on a circum‐Antarctic scale. Experiments conducted for the 2005–2006 season provide a mean fast ice‐algal production estimate of 2.8 Tg C/y. This estimate represents about 12% of overall Southern Ocean sea‐ice algae production (estimated in a previous study), with the mean fast‐ice algal production per area being 3.3 times higher than that of pack ice. Our Antarctic fast‐ice GPP estimates are probably underestimated in the Ross Sea and Weddell Sea sectors because the sub‐ice platelet layer habitats and their high biomass are not considered.

Comprehensive evaluation of using mineral and bio phosphorus fertilization on orange tree (Citrus sinensis) productivity

Phosphorus (P) is considered as an essential element in crop production. Besides, the study of P from the elemental and bio sources impacts on productivity and quality of orange trees could emphasize its utilization importance. This study aimed to evaluate the chemical implication of three treatments of P fertilization (Triple phosphate (TP; 620 and 900 g/tree/year), phosphate rock (PR; 1820 and 2742 g/tree/year) and 1:1 TP:PR on Valencia orange trees (Citrus sinensis L. Osbeckunder). Where, all these treatments were equipped with bio-phosphorus fertilizer (phosphorin) (0 and 5 g/tree/year added twice in the year, Feb. and Jun.). The measurements included leaves nitrogen (N), phosphorus (P) and Potassium (K), number of fruits (NoF), juice weight/volume, total soluble solids (T.S.S.), vitamin C (V.C), and acidity. The results showed that the treatment (50% TP +50% PR at 450+1371g/tree/year + phosphourin at 5g/tree/year) gave the highest values for all characters i.e. N % in tree leaves 2.61 and 2.69%, P% in tree leaves 0.16 and 0.17%, K in tree leaves 1.79 and 1.86%, number of fruits/tree 412.0 and 420.0, fruit weight 267.0 and 280.0g, fruit weight/tree 110.0 and 117.60kg, fruit size 260.41 and 272.37cm3, juice weight 114.1 and 126.15g, fruit juice 44.33 and 44.99%, juice volume 110.15 and 114.90cm3, peel thickness 0.58 and 0.60cm, T.S.S. 12.14 and 12.21%, T.S.S. / Acid ratio 9.07 and 9.41, and V.C 70.15 and 72.44 (mg/100 ml) as well as the lowest total acidity 0.93 and 0.91%, under both the 1st season and the 2nd one, respectively. In conclusions, as the application of bio-fertilization has improved the quality charcatistics over seasons. Thus, this study opens the way towards the advanced application of bio-P element to understand the biogeochemical cycles, dynamics and function of natural ecosystems elements in agricultural and food security program.

Foraminiferal denitrification and deep bioirrigation influence benthic biogeochemical cycling in a seasonally hypoxic fjord

Benthic macro- and micro-biota often play significant roles in controlling the biogeochemical dynamics in sediments. Their activity can be influenced by oxygen availability and impacted by the rise in global hypoxia in coastal regions over the last decades. To understand how these organisms interact with coastal hypoxia and influence sediment biogeochemistry, we undertook a study of early diagenesis in Bedford Basin, a seasonally hypoxic fjord on the West Atlantic coast in Nova Scotia, Canada, using a combination of observations and reaction-transport modeling. We observed that the seafloor was a source of ammonium and sink of nitrate with average fluxes of 2.2 ± 1.8 and −0.9 ± 0.7 mmol m−2 d−1 respectively. The diffusive oxygen uptake was 14 ± 4.6 mmol m−2 d−1 and the total organic carbon content in collected sediment cores was 5–7 % with a C/N ratio of ∼10. The pyrite content increased steadily from 0.5 wt% Fe at surface to ∼2 wt% Fe at 20 cm depth. Hydrogen sulfide was negligible down to 25 cm depth most of the time. The sediment was inhabited by tube-forming polychaete Spiochaetopterus sp. that formed tubes up to ∼30 cm in length. The living foraminiferal assemblage in the top 5 cm sediment was found to be dominated (>85 %) by nitrate-storing and denitrifying benthic foraminifera Stainforthia fusiformis. These observations were used to develop and constrain a biogeochemical reaction-transport model. The model results suggest that the observed decrease in porewater concentrations of ammonium and dissolved inorganic carbon below 5 cm depth, was due to deep bioirrigation by tubeworms, accounting for almost 50 % of the benthic efflux. The model further revealed that the deep bioirrigation along with bioturbation and iron cycling prevented accumulation of free sulfide in the top 25 cm sediment despite oxygen penetration depths of ∼1 mm. Modelled organic carbon and nitrogen deposition was 25.2 and 2.9 mmol m−2 d−1 with burial efficiencies of 23 % and 17 %, respectively. The model indicated a total denitrification rate of 1.3 mmol N m−2 d−1 that was largely (∼70 %) driven by benthic foraminifera. This study reports the first evidence of foraminiferal denitrification in western Atlantic coastal sediments, and suggests that eukaryote mediated denitrification is an important driver of sediment N-loss in seasonally hypoxic environments, a process that has been traditionally assumed to be carried out by prokaryotic microbes.