Understanding Of Nutrient Dynamics Research Articles

Characterization of the distribution of mineral elements in chromium-stressed rice (Oryza sativa L.) leaves based on laser-induced breakdown spectroscopy and data augmentation

The fast and precise visualization of mineral elements in contaminated plants is crucial for understanding nutrient dynamics, plant health, and environmental monitoring. In this study, a Wasserstein generative adversarial network (WGAN) is proposed to expand the data scale and combines laser-induced breakdown spectroscopy (LIBS) with three machine learning methods for mineral elements analysis in Cr-stressed rice (Oryza sativa L.) leaves. In the quantitative analysis of mineral elements, the proposed method improved the prediction performance for Cu, K, Mg, Mn, and Na, except for Ca and Fe, demonstrating the effectiveness of data augmentation in enhancing the quantitative models. Mapping the distribution of Ca, Fe, Mg, K, Mn, and Na in rice leaves shows higher concentrations towards the apical regions and approximately symmetrical distribution along the leaf vein. Additionally, Fe, K, and Mn concentrations are significantly lower in Cr-polluted leaves compared to uncontaminated leaves. These preliminary findings offer insights into the macro distribution of mineral elements in plants.

Improving the identification of pollution source areas with catchment-resolution sensitivity analysis

The significant impacts of total nitrogen (TN) and total phosphorus (TP) on riverine ecosystems underscores the critical need to identify the primary nutrient source areas in watersheds. This study aims to unravel the influences of terrain and land use types on mean monthly TN (TNM) and mean monthly TP (TPM) export across varying catchment resolutions in the Qiantang River Watershed of China. The findings of this study illuminated the critical role of topography in understanding nutrient dynamics, wielding a profound influence over water flow patterns and nutrient dispersion. Both land slope and Stream Power Index (SPI) displayed substantial negative correlations (r < −0.6) with TNM and TPM concentrations, whereas the Topographic Wetness Index (TWI) showed positive correlations with the nutrient indexes. In addition to terrain characteristics, impervious land surfaces had a positive correlation with nutrient concentrations, while grassland and forest areas exhibited negative correlations. Results further underscored the substantial influence of catchment resolution on correlations between watershed properties and riverine nutrient concentrations. It was imperative to choose an effective catchment resolution in watershed delineation – not too coarse, nor too fine – to accurately capture the topographic and land use impacts on nutrient dynamics. With the most appropriate catchment size (Catchment 700 km2), the critical pollution source areas for TN and TP pollution were identified, and thus could be used to guide future pollution reduction efforts. The study not only highlights the importance of identifying an appropriate catchment size for water pollution, but also emphasizes the necessity of effectively extracting critical pollution source areas to mitigate water nutrient pollution and increase the ecological integrity of the Qiantang River Watershed.

Distribution of nutrients and dissolved organic matter in a eutrophic equatorial estuary: the Johor River and the East Johor Strait

Abstract. Estuaries have strong physicochemical gradients that lead to complex variability and often high rates of biogeochemical processes, and they are also often impacted by humans. Yet, our understanding of estuarine biogeochemistry remains skewed towards temperate latitudes. We examined seasonal and spatial variability in dissolved organic matter (DOM) and nutrients along a partly eutrophic, agricultural–urban estuary system in Southeast Asia: the Johor River and the East Johor Strait. Dissolved organic carbon (DOC) and coloured DOM (CDOM) showed non-conservative mixing, indicating significant DOM inputs along the estuary. The CDOM spectral slopes and CDOM : DOC ratios suggest that terrigenous, soil-derived DOM dominates along the Johor River, while phytoplankton production and microbial recycling are important DOM sources in the Johor Strait. CDOM properties were not unambiguous source indicators in the eutrophic Johor Strait, which is likely due to heterotrophic CDOM production. Nitrate concentrations showed conservative mixing, while nitrite concentrations peaked at intermediate salinities of 10–25. Ammonium concentrations decreased with salinity in the Johor River but increased up to 50 µmol L−1 in the Johor Strait, often dominating the dissolved inorganic nitrogen (DIN) pool. Phosphate concentrations were low (&lt;0.5 µmol L−1) throughout the Johor River but increased in the Johor Strait, where DIN : phosphate ratios were typically ≥ 16 : 1. This suggests that the Johor Strait may experience phosphorus limitation and that internal recycling is likely important for maintaining high nutrient concentrations in the Johor Strait. Overall, our results indicate that the Johor River and Johor Strait are clearly not part of the same estuarine mixing continuum and that nutrient recycling processes must be quantified to understand nutrient dynamics in the Johor Strait. Moreover, our results highlight the need for better techniques for DOM source tracing in eutrophic estuaries.

Multiple nutrient limitation of the soil micro-food web in a tropical grassland revealed by nutrient-omission fertilization

Although involved in key functions of the terrestrial ecosystems, the activity and the diversity of soil microorganisms can be severely limited by energy and nutrients in weathered tropical soils. To optimize nutrient cycling for crop nutrition, assessing which nutrients limit the activity of the microbial food web is thus essential. This was our aim in this study carried out on a tropical ferrallitic soil from a natural grassland in Madagascar. For this purpose, we employed an innovative nutrient-omission approach in microcosms to test the distinct effects of omitting C, six nutrients (N, P, K, S, Ca, Mg) and a cocktail of micronutrients (B, Mn, Cu, Na and Mo) on the composition, biomass and activities of the microbial community and on the abundance and biomass of their nematode grazers. C and P were identified as primary limitations, but other nutrients (N, Mg and S) played significant roles as co-limiting factors. Some bacterial and fungal taxa were significantly associated to specific nutrient deficiencies and can act as biological indicators. Additionally, the abundance and biomass of microbial-feeding nematodes provided valuable insights into the responses of the soil microbial community to nutrient deficiencies. These findings contribute to our understanding of nutrient dynamics and microbial community growth in tropical grassland ecosystems and have implications for sustainable crop fertility management and ecosystem ecology in similar environments.

Mineral Nitrogen Release Patterns in Various Soil and Texture Types and the Impact of Urea and Coated Urea Potassium Humate on Barley Biomass

Controlled-release urea fertilization is an innovative approach and effective means to reduce the loss of nitrogen and enhance fertilizer use efficiency to optimize crop yield while minimizing the environmental impact. The objective of this study was to investigate the dynamic process of mineral nitrogen (Nmin) release in Luvisols, Cambisols, Retisols, and Arenosols to understand the interaction between soil characteristics and mineral nitrogen release and evaluate the impact of conventional urea compared to coated urea potassium humate on barley biomass production. A pot experiment was conducted under glasshouse conditions (20 ± 2 °C and 60% Humidity). Five treatments including no fertilization as a control (C), 100 kg·N·ha−1 of urea (U100), 200 kg·N·ha−1 of urea (U200), 100 kg·N·ha−1 of coated urea potassium humate (UPH100), and 200 kg·N·ha−1 of coated urea potassium humate (UPH200) were applied to four soil and texture types. Our findings indicate that there are different patterns of mineral nitrogen release across the different soil and texture types. Ammonium levels reached their peak point in all soils within 2–7 days after application. On the other hand, the concentration of nitrate NO3−–N showed a linear increase over 45 days during the experiment. The Retisol, which had a sandy clay texture, obtained the highest concentration of mineral nitrogen in both forms (NH4 and NO3), while the sandy texture of Arenosol showed the lowest accumulation of mineral nitrogen and its forms. The application of potassium humate caused a delay of 1–4 days in the peak of soil ammonium, which at peak accounted for approximately 25–44% of the mineral nitrogen in the soil. Furthermore, the application of urea and coated urea potassium humate exhibited significant effects on barley biomass with an increase of approximately 14–91% compared to the unfertilized treatment (control). This research contributes to our understanding of nutrient dynamics in diverse soil environments and provides insights into optimizing sustainable fertilization strategies such as controlled-release fertilizer application. The implications of these findings highlight the significance of tailored nutrient management practices based on soil texture type, which can lead to improved agricultural productivity and environmental impact.

Ecological Stoichiometry of N and P across a Chronosequence of Chinese Fir Plantation Forests

Ecological stoichiometry is crucial in understanding nutrient dynamics and its impact on plant growth and development at various ecological scales. Among the different nutrients, nitrogen (N) and phosphorus (P) have been widely recognized as key elements regulating substance transport, energy utilization, and ecosystem conversion. The N:P ratio in plants serves as a sensitive indicator of ecological processes, reflecting the availability and balance of these nutrients. Therefore, studying the ecological stoichiometry of N and P is essential for accurately assessing soil fertility and site productivity, particularly in forest ecosystems with low-fertility soils. In this study conducted in Huitong, Hunan province, southern China, the contents of N and P, as well as the N:P ratios, were investigated in plant-soil systems across four different aged stands of Chinese fir forests (3-, 8-, 18-, and 26-year-old stands). The results revealed varying concentrations of N and P in soils and foliage across the different plantations. Soil N concentrations increased by approximately 4%, 30%, and 22% in 8-, 18-, and 26-year-old plantations compared to the 3-year-old plantation. Soil P concentration was significantly higher in 8-, 18-, and 26-year-old plantations compared to the 3-year-old plantation. The average soil N:P ratio followed the order of 3-year-old plantation &gt; 18-year-old plantation &gt; 26-year-old plantation &gt; 8-year-old plantation. Regarding foliage, both N and P contents exhibited a similar pattern across the different aged leaves, with current-year-old leaves having higher concentrations than 1-year-old, 2-year-old, and 3-year-old leaves in all four Chinese fir plantations. The study further established relationships between soil and foliage nutrient ratios. Soil N:P ratio was positively correlated with soil N content but negatively associated with soil P content. The foliage N:P ratio also showed a significant negative correlation between leaf N and foliage P content. These findings suggest that soil nutrient conditions improved with the aging of Chinese fir plantations, mainly due to increased inputs of above- and below-ground litter. Overall, this study provides valuable insights into the ecological stoichiometry of N and P in Chinese fir plantations, offering a scientific basis for sustainable forest management practices in southern China.

Ovarian morphology and oocyte development in the seabob shrimp Xiphopenaeus kroyeri: a histological and histochemical approach for the study of penaeid reproduction

Histological and histochemical changes during oocyte development were evaluated in order to establish a model for better understanding nutrient dynamics throughout vitellogenesis and overall penaeid reproduction. Samples of Xiphopenaeus kroyeri females (n = 587) at different stages of gonadal maturation were subjected to histological and histochemical analysis for the identification of neutral polysaccharides, total proteins, and tissue differentiation. We observed that the ovarian structure was composed of collagen fibers and oviducts were lined by three layers of epithelium separated by muscular tissue. Oogenesis was classified into six distinct phases: chromatin nucleolar oocytes, chromatin perinucleolar oocytes, oocytes in primary vitellogenesis, oocytes in secondary vitellogenesis, mature oocytes, and atretic oocytes. Histochemical observations suggested that during the previtellogenesis phase, proteins and neutral polysaccharides were not present. However, a progressive increase in these substances occurred from vitellogenic oocytes until their final maturation stage. Follicular cells composed the follicular complex forming an external epithelium in vitellogenic oocytes, and are probably involved in protein transfer during maturation process. Collagen and glycoprotein vesicles were identified in the cytoplasm of mature oocytes of X. kroyeri. Taken together, the present findings contribute to the current knowledge on the ovarian morphology and maturation process of penaeids, supporting future studies on reproductive biology and breeding performance in captivity.

Understanding nutrient dynamics for effective stormwater treatment design

Current stormwater quality modelling tools lack robust mathematical replication of nutrient entrainment in runoff. This makes it challenging to design effective stormwater treatment systems such as nature based solutions with adequate resilience to future changes in nutrient inputs in urban environments. Consequently, poorly treated stormwater can be discharged into receiving waters, leading to nutrient enrichment and in turn, environmental and human health impacts. This study integrated empirically based with statistical modelling techniques to incorporate nutrient dynamics into commonly used Intensity-Frequency-Duration (IFD) distributions of design rainfall. Field based nutrient wash-off experiments were conducted to understand nutrient behaviour during a runoff event. New mathematical formulations were derived to describe the decay (wash-off) of nutrients. Rainfall intensity, duration and initially accumulated pollutant load exert positive influence on the decay of nitrogen and phosphorous, while organic carbon has a negative impact on phosphorus decay. It was also evident that nitrogen species would decay at a similar rate, while phosphorus species may decay at different rates. Compared to nitrogen species, phosphorous species were found more likely to be washed-off during a rainfall event. Using the mathematical formulations developed, wash-off of nitrogen and phosphorous was simulated for 435 very frequent and frequent/infrequent design rainfall events leading to the creation of Intensity-Frequency-Duration-Wash-off (IFDW) curves. Analysis of uncertainty associated with IFDW indicated that total phosphorous could be completely washed-off during most of the design rainfall events, while total nitrogen would only be completely washed-off by very few events that are rarer than 10 % AEP (annual exceedance probability). IFDW can act as a tool for supporting effective stormwater treatment design in order to promote sustainable stormwater management and reuse.

Accumulated litter, nutrient stock and decomposition in an Atlantic Forest fragment

Litter dynamics is one of the fundamental processes for the growth and maintenance of native forest fragments, being considered the main pathway for nutrient cycling in forests. Therefore, studies on accumulated litter and nutrient content provide information for a better understanding of nutrient dynamics. The aim of the study was to evaluate leaf litter and nutrient stock in different seasons and the instantaneous rate of decomposition in an Atlantic Forest Fragment over two years. Litter sampling was carried out in 12 permanent plots with dimensions of 20 m x 50 m. Litter dry mass and nutrient concentration were determined. The average annual accumulation of litter was 5269 kg ha-1. There was no statistically significant difference in the amount of litter between seasons. There was a statistically significant difference in the contents of N, P, K Ca and Mg between the different seasons. Nutrient stocks were 123.3, 92.8, 13.2, 11.8, 9.6, 3.0 kg ha-1 year-1 for Ca, N, Mg, S, K and P respectively. The total of nutrients in the accumulated litter was 253.7 kg ha-1 year-1. The litter renewal time was 281 days. The times required for 50% and 95% litter decomposition were 196 and 850 days. The average litter stocks, nutrients and decomposition are in line with other studies, indicating that the Atlantic Forest fragment seasonal semi-deciduous presents indicators of nutrient cycling. These results show that the ecosystem is sustainable from the point of view of cycling and nutrient release.&#x0D; Keywords: ecosystem functions, nutrient cycling, secondary succession.

Seasonal litterfall and nutrients in an Atlantic Forest fragment

Litter dynamics is one of the fundamental processes for the growth and maintenance of native forest fragments, being considered the main pathway for nutrient cycling in forests. Studies on litter production and nutrient content therefore provide insights that provide a better understanding of nutrient dynamics. This study identifies the seasonality and meteorological conditions that influence the quantity and return of nutrients through litter in an Atlantic Forest fragment. Litter sampling was carried out monthly in 12 permanent plots. Each plot contained 5 littertraps distributed systematically. The litter was classified, and the dry mass and nutrients in the leaves and branches and miscellaneous fractions was quantified. Seasonal behavior was observed, with the highest depositions in the winter season. The average annual production was 6.78 Mg ha-1, with 64.9% being composed of leaves. The mean annual nutrient intake was 135.1, 115.7, 39.7, 23.5, 17.6 and 4.6 kg ha-1 for Ca, N, K, Mg, S and P, respectively. The meteorological variable precipitation influenced the deposition pattern. The increase in nutrient-use efficiency in the second year compared to the first indicates that plants strategically may be re-translocating relative amounts of their nutrients under water stress conditions.&#x0D; Keywords: ecosystem functions, nutrient cycling, secondary succession.

Evaluation of nutrients removed and recycled in a commercial peach orchard over a 14-years-production cycle

Understanding nutrient dynamics within a peach orchard is fundamental to the development of accurate nutrient management practices. The present study investigated the nutrient uptake and redistribution in a 14-years-old commercial orchard in the Po valley. At the end of the experiment, trees were harvested, biomass and organ nutrient concentration were determined. Skeleton and roots accounted for the highest plant biomass, followed by fruits at harvest, pruned wood and abscised leaves; thinned fruits were less than 1 kg tree-1. The difference between the amounts of nutrients in leaves sampled in summer and in autumn (at abscission) was used to estimate the fraction of nutrients remobilized during the vegetative season inside the tree. The decrease of N, P, S, Cu, Mn and Zn concentration in abscised, compared to summer-sampled leaves was the result of the translocation of nutrients into fruits and storage organs. Nutrient circulation in a commercial nectarine orchard was calculated by determination of the fractions of each nutrient recycled (sum of nutrients in abscised leaves, thinned fruits and pruned wood) and remobilized (sum of nutrients in fruits at harvest, roots and skeleton). In our experimental conditions, on average, nectarine Stark RedGold showed an annual request of (in kg ha-1) 100, 17, 73, 129, 16, and 6 of N, P, K, Ca, Mg and S, respectively. More than half of these quantities were recycled in the orchard and returned back to the soil; consequently, if the nutrient use efficiency is maximized, the fertilization of nectarine requires only small amount of external inputs.

Spatio-temporal variation in stable isotope and elemental composition of key-species reflect environmental changes in the Baltic Sea

Carbon and nitrogen stable isotope ratios are increasingly used to study long-term change in food web structure and nutrient cycling. We retrospectively analyse elemental composition (C, N and P) and stable isotopes (δ13C, δ15N) in archived monitoring samples of two important taxa from the bottom of the food web; the filamentous ephemeral macroalgae Cladophora spp. and the blue mussel Mytilus edulis trossulus from three contrasting regions in the Baltic Sea (coastal Bothnian Sea and Baltic Proper, open sea central Baltic). The aim is to statistically link the observed spatial and interannual (8–24 years’ time-series) variability in elemental and isotope baselines with their biomass trends and to the oceanographic monitoring data reflecting the ongoing environmental changes (i.e., eutrophication and climate) in this system. We find clear differences in isotope baselines between the two major Baltic Sea basins. However, the temporal variation in Mytilus δ13C was similar among regions and, at the open sea station, mussels and algae δ13C also correlated over time, likely reflecting a global (Suess) effect, whereas δ15N of both taxa varied with local and regional dissolved nitrogen concentrations in water. δ15N in source amino acids allowed detection of diazotrophic N in Mytilus, which was masked in bulk δ15N. Finally, Cladophora N:P reflected regional nutrient levels in the water while P%, which differed for both taxa, was linked to food quality for Mytilus. This study highlights the potential of a multi-taxa and multi-stable isotope approach to understand nutrient dynamics and monitor long-term environmental changes.

Nutrient stoichiometry of fishes and invertebrates in coastal marine Caribbean ecosystems.

The importance of animals for mediating ecosystem processes has long been recognized by ecologists. Traditionally, consumer-mediated dynamics have been considered through consumptive pathways such as predation and herbivory. Yet, consumers also play critical roles in mediating "bottom-up" pathways associated with nutrient dynamics. Foundational research demonstrated the importance of these dynamics in terrestrial, freshwater, and pelagic marine ecosystems, and introduced novel perspectives on the role of animals such as wildebeest, lacustrine fishes, and zooplankton, respectively, for providing an important source of nutrients that limit primary production. This research inspired a substantial body of research on the importance of consumer-mediated nutrient dynamics for ecosystem function. Despite this, only recently have ecologists begun to extend this line of thinking toward coastal marine ecosystems. The data presented herein is a comprehensive study of consumer nutrient dynamics from invertebrates and fishes that live in subtropical and tropical Caribbean coastal marine waters, including mangroves, seagrass beds, and coral reefs. This data set represents the largest, to my knowledge, published nutrient stoichiometry data set from a single system, including estimates of excretion rates (n = 900 individuals total; n = 667 individual fish, size range 0.14-2,597 g [2-107 cm]; n = 233 invertebrates, size range 0.04-487 g), and somatic nutrient content analyses (n = 658 individuals total, n = 494 vertebrates, n = 164 invertebrates). These data also include δ13 C and δ15 N stable isotopes of whole body, body mass (wet mass), taxonomic identification to class-level, and functional group classification. These data have been used to test basic ecological theory, to scale individual-level processes to coral reef, mangrove, and seagrass ecosystems, and to understand the role of human impacts for mitigating consumer-mediated nutrient dynamics. While these findings have helped improve our understanding of nutrient dynamics in tropical coastal ecosystems, these data offer a wealth of additional promise for advancing ecological theory and applied science in tropical marine ecosystems and beyond. Users are free to use and analyze the data. Attribution should be given to this presentation of the data.

Spatial distribution patterns of nitrogen and phosphorus in water and bed sediment of the Three Gorges Reservoir

Nutrient state in the Three Gorges Reservoir has long been concerned. Mainstream of the reservoir however has received relatively less researchers’ attention compared to tributaries. In 2015–2017, we sampled 40 cross-sections along mainstream and 10 tributaries in flood and dry seasons in order to reveal lateral, vertical, and longitudinal distribution patterns of total nitrogen (TN) and phosphorus (TP) in water and sediment. Concentrations of waterborne TN and TP ranged from 1.48 to 2.33 mg/L and 0.09 to 0.16 mg/L respectively. Laterally, nutrients were well mixed and homogeneously distributed. Vertically, nutrients concentrations in surface water were higher than in bottom water. Longitudinally, TN concentration increased from tail to head of the reservoir due to accumulation of nitrogen imported from riparian zone and tributaries, whereas TP concentration decreased from tail to head because of sediment deposition. TN and TP concentrations in channel bed sediment were 622–949 and 916–950 mg/kg respectively. Neither of them had significant longitudinal trends nor correlations with waterborne nutrient concentrations. This work will help to understand nutrient dynamics in the Three Gorges Reservoir.

Allocation strategies of carbon, nitrogen and phosphorus following a gradient of wildfire severities

AbstractWildfire is crucial in the regulation of nutrient allocation during the succession of boreal forests. However, the allocation strategies of carbon (C), nitrogen (N) and phosphorus (P) between leaves and fine roots in response to wildfire severities remain poorly studied. We aimed to explore the allocation strategies of C, N and P between leaves and fine roots among different fire severities. We selected four wildfire severities (unburned, low, moderate and high severity) after 10 years recovery in the Great Xing’an Mountains, northeast China, and compared C, N and P concentrations in leaves and fine roots of all species among fire severities using stoichiometry theory and allometric growth equations. Compared with unburned treatment, C concentrations in leaves and fine roots increased at low severity, and leaf N concentration was the greatest at high severity, but the lowest fine root N concentration occurred at high severity. Plant nutrient utilization tended to be P-limited at high fire severity according to the mean value of N:P ratio &amp;gt; 16. More importantly, C, N and P allocation strategies between fine roots and leaves changed from allometry to isometry with increasing fire severities, which showed more elements allocated to leaves than to fine roots with increasing fire severities. These changes in patterns suggest that the allocation strategies of elements between leaves and fine roots are of imbalance with the wildfire severity. This study deepens our understanding of nutrient dynamics between plant and soil in ecosystem succession.

Nutrient dynamics from surface‐applied organic matter amendments on no‐till orchard soil

AbstractAdvancing conservation agriculture depends on understanding nutrient dynamics of organic matter amendments (OMA) on no‐till soil. This field incubation study compared surface‐applied composted dairy manure (CM), green waste compost (GWC) and an unamended control from March to September in 2015 and 2016 using a RCBD in a California almond (Prunus dulcis) orchard. Measurements included OMA nutrient release rates, changes in soil organic carbon (SOC), total N (TN) and inorganic N, P and K availability using in‐season soil sampling and collection of ion exchange resin (IER) membranes from 0 to 10 cm depth, and cumulative N and P availability using soil IER cores from 0 to 50 cm depth. We hypothesized OMA sources with a lower initial C:N increase soil N availability, greater soluble phosphorus (P) and potassium (K) concentrations increase P and K availability, and all OMA sources increase SOC with the greatest N recovery in the TN pool. No differences were observed in C, N and P release rates, while the K release rate was the greatest. In‐season N availability showed no effect but P and K availability differed as evidenced by greater IER adsorption and soil extractable P and K. Both OMA sources significantly increased in SOC and TN. Net N mineralization from OMA sources ranged from 0.7% to 8.0% of applied N and total N recovery in TN and inorganic N pools increased based on the initial C:N. These results advance our understanding of nutrient dynamics while conserving the soil due to the no‐till practice of surface‐applied OMA.

Excess nitrogen in the Bohai and Yellow seas, China: Distribution, trends, and source apportionment

The Bohai and Yellow seas are marginal seas of the western North Pacific, characterized by coastal eutrophication and populated coastlines. In this work, six survey datasets collected between 2011 and 2018 were used to investigate the excess of dissolved inorganic nitrogen (DIN) related to soluble reactive phosphorus (SRP), referred to as N*, in the Bohai and Yellow seas. High N* of more than 5 μmol kg−1 occurred mostly in the Changjiang and Yellow River plumes and/or near the Jiangsu coast. Away from these river plumes and the Jiangsu coast, however, N* usually ranged from −2.5 to 1.0 μmol kg−1. Combining our field data and previously published data, we found that N* in the Bohai and Yellow seas increased in the 1990s and 2000s, likely caused by the combined effect of atmospheric nitrogen deposition increase and the Kuroshio N* rise. In the 2010s, however, the coastal N* increases stopped. Based on a N*-budgeting approach, marine N (either from in situ decomposition of marine organic matters or from the open seas via current inputs) and non-marine N (either from riverine inputs or from local atmospheric nitrogen deposition) were distinguished. Marine N accounted for 51% ± 38% of DIN in the Bohai Sea and 67% ± 37% of DIN in the Yellow Sea. Although this is a regional study, we suggest that accumulation of atmospheric nitrogen along oceanic circulation pathways dominates the decadal evolution of coastal eutrophication. These findings and new insights may improve management of eutrophication in these two important marginal seas, and will also improve our understanding of nutrient dynamics in other marine systems.

Macronutrient Management Effects on Nutrient Accumulation, Partitioning, Remobilization, and Yield of Hybrid Maize Cultivars.

It is critical to understand nutrient dynamics within different plant parts to correctly fine-tune agronomic advices, and to update breeding programs for increasing nutrient use efficiencies and yields. Farmer’s field-based research was conducted to assess the effects of nitrogen (N), phosphorus (P), and potassium (K) levels on dry matter and nutrient accumulation, partitioning, and remobilization dynamics in three popular maize (Zea mays L.) hybrids (P3522, P3396, and Rajkumar) over two years in an alluvial soil of West Bengal, India. Experimental results revealed that NPK rates as well as different cultivars significantly (p ≤ 0.05) influenced the dry matter accumulation (DMA) in different plant parts of maize at both silking and physiological maturity. The post-silking dry matter accumulation (PSDMA) and post-silking N, P, and K accumulations (PSNA, PSPA, PSKA) were highest in cultivar P3396. However, cultivar P3522 recorded the highest nutrient remobilizations and contributions to grain nutrient content. Total P and K accumulation were highest with 125% of the recommended dose of fertilizer (RDF) while total N accumulation increased even after 150% RDF (100% RDF is 200 kg N, 60 kg P2O5, and 60 kg K2O ha–1 for the study region). Application of 125% RDF was optimum for PSDMA. The PSNA continued to increase up to 150% RDF while 125% RDF was optimum for PSPA. Cultivar differences significantly affected both remobilization efficiency (RE) and contribution to grain nutrient content for all tested macronutrients (N, P, and K). In general, RE as well as contribution to grain nutrient content was highest at 125% RDF for N and K, and at 100% RDF for P (either significantly or at par with other rates) for plots receiving nutrients. For all tested cultivars, nutrient remobilization and contribution to grain nutrient content was highest under nutrient-omission plots and absolute control plots. Both year and cultivar effects were non-significant for both grain and stover yields of maize. Application of 75% RDF was sufficient to achieve the attainable yield at the study location. The cultivar P3522 showed higher yield over both P3396 and Rajkumar, irrespective of fertilizer doses, although, the differences were not statistically significant (p ≥ 0.05). The study underscores the importance of maize adaptive responses in terms of nutrients accumulation and remobilization at different levels of nutrient availability for stabilizing yield.

Modelling bivalve culture - Eutrophication interactions in shallow coastal ecosystems

Assessing the carrying capacity of ecosystems is crucial to the selection of suitable and sustainable locations for aquaculture farms. In Malpeque Bay (PEI, Canada), the potential expansion of mussel farms has driven a series of numerical modelling studies. We coupled sub-models for sea lettuce, wild and cultured oysters and wild softshell clams to an existing ecosystem model to better understand nutrient dynamics and the carrying capacity of Malpeque Bay. Simulations suggested that competition for nutrients between phytoplankton and sea lettuce and filtration by cultured bivalves predominantly mitigate eutrophication effects. The addition of sea lettuce reduced mussel growth by 2% on average and up to 9% near eutrophic estuaries favouring macroalgae growth. Projected new mussel farms reduced current mussel growth by 2% also, suggesting that the carrying capacity of the bay may not be reached yet. Both current and projected aquaculture activities seemed to have limited effects on natural bivalve growth.

Integrated Seed Proteome and Phosphoproteome Analyses Reveal Interplay of Nutrient Dynamics, Carbon-Nitrogen Partitioning, and Oxidative Signaling in Chickpea.

Nutrient dynamics in storage organs is a complex developmental process that requires coordinated interactions of environmental, biochemical, and genetic factors. Although sink organ developmental events have been identified, understanding of translational and post-translational regulation of reserve synthesis, accumulation, and utilization in legumes is limited. To understand nutrient dynamics during embryonic and cotyledonary photoheterotrophic transition to mature and germinating autotrophic seeds, an integrated proteomics and phosphoproteomics study in six sequential seed developmental stages in chickpea is performed. MS/MS analyses identify 109 unique nutrient-associated proteins (NAPs) involved in metabolism, storage and biogenesis, and protein turnover. Differences and similarities in 60 nutrient-associated phosphoproteins (NAPPs) containing 93 phosphosites are compared with NAPs. Data reveal accumulation of carbon-nitrogen metabolic and photosynthetic proteoforms during seed filling. Furthermore, enrichment of storage proteoforms and protease inhibitors is associated with cell expansion and seed maturation. Finally, combined proteoforms network analysis identifies three significant modules, centered around malate dehydrogenase, HSP70, triose phosphate isomerase, and vicilin. Novel clues suggest that ubiquitin-proteasome pathway regulates nutrient reallocation. Second, increased abundance of NAPs/NAPPs related to oxidative and serine/threonine signaling indicates direct interface between redox sensing and signaling during seed development. Taken together, nutrient signals act as metabolic and differentiation determinant governing storage organ reprogramming.