Variations In Nutrient Concentrations Research Articles

Immersed Boundary Approach to Biofilm Spread on Surfaces

We propose a computational framework to study the growth and spread of bacterial biofilms on interfaces, as well as the action of antibiotics on them. Bacterial membranes are represented by boundaries immersed in a fluid matrix and subject to interaction forces. Growth, division and death of bacterial cells follow dynamic energy budget rules, in response to variations in environmental concentrations of nutrients, toxicants and substances released by the cells. In this way, we create, destroy and enlarge boundaries, either spherical or rod-like. Appropriate forces represent details of the interaction between cells, and the interaction with the environment. Numerical simulations illustrate the evolution of top views and diametral slices of small biofilm seeds, as well as the action of antibiotics. We show that cocktails of antibiotics targeting active and dormant cells can entirely eradicate a biofilm.

Genotype-by-Environment Interaction for the Contents of Micro-Nutrients and Protein in the Green Pods of Cowpea (Vigna unguiculata L. Walp.)

Cowpea (Vigna unguiculata L. Walp.) is a drought-tolerant legume crop widely cultivated in arid and semi-arid regions of sub-Saharan Africa (SSA), including South Africa. The leaves, young and immature pods, and grains of cowpea are a vital source of plant-based proteins and essential nutrients for human wellbeing. The objective of this study was to determine the effect of genotype-by-environment interaction (GEI) on the contents of micro-nutrients and protein content of the green pods of cowpea to recommend superior genotypes for cultivation and breeding. Fifteen genetically diverse cowpea genotypes were evaluated across six test environments in South Africa, using a randomized complete block design replicated three times. Micro-nutrients such as iron (Fe), manganese (Mn), zinc (Zn), and total protein (TP) content were determined in the immature pods of cowpea. Data were subjected to additive main effects and multiplicative interaction (AMMI) analysis. Significant (p < 0.05) genotype (G) differences were detected for Fe, Mn, Zn and TP, suggesting the presence of genetic divergence for selection. Furthermore, a significant (p < 0.05) environment (E) effect was recorded for all studied nutrient, indicating the impact of the test environments on nutrient compositions. The GEI effect was significant for all the assessed nutrients, indicating that specific and broadly adapted genotypes could be identified. Based on best linear unbiased estimates (BLUEs) and best linear unbiased predictors (BLUPs) analyses, the following ranges of nutrient compositions were observed: Fe (83.70–109.03 and 69.77–134.16 mg/kg), Mn (20.60–33.83 and 18.75–36.83 mg/kg), Zn (33.79–40.53 and 28.81 mg/kg), and TP (22.37–24.54 and 21.44–25.25 mg/kg), respectively, across the tested environments. The AMMI test procedure (FR-test) identified the first interaction principal component axis (IPCA-1) to be a significant (p < 0.05) component of the GEI, explaining >91% of phenotypic variation in nutrient contents among the tested genotypes across environments. Cowpea genotypes Meterlong Bean and TVU-14196 were identified for their high Fe, Zn and Mn contents and recommended for cultivation in Mafikeng, Potchefstroom and Roodeplaat in South Africa. For TP, genotypes Meterlong Bean and Kisumu Mix had stable performance and are recommended for production at all the test environments. The identified genotypes are recommended for future cultivation and breeding to supplement micro-nutrients and protein and combat nutrient deficiencies and malnutrition in South Africa.

Effects of Pollution Control of Xiaoqing River on Environment Factors and Phytoplankton Community in the Laizhou Bay

The spatial distribution of environmental factors, chlorophyll a (Chla), phytoplankton abundance, and community structure in the Laizhou Bay were investigated in August 2018 (wet season after pollution control) to clarify the effects of the pollution control of the Xiaoqing River, which is a major source of pollution, on environmental factors and phytoplankton community structure in this area. The results showed that the environmental factors changed significantly after pollution control of the Xiaoqing River. The concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic silicon (DSi), NO3-, and NO2- decreased significantly, with values only 40.1% to 60.4% of those from the same period of in 2017 (the nearest year before the pollution control), whereas dissolved inorganic phosphorus (DIP) and NH4 increased by 2.5 and 1.4 times that of their concentrations in 2017. The spatial distribution of environmental factors changed significantly, with the nutrient concentrations around the Xiaoqing River estuary noticeably decreasing. The abundance of phytoplankton cells was 21.5×106 cell·m-3, which was close to the results of a previous study, whereas the ρ(Chla) was 2.43 μg·L-1, which decreased obviously. Both microscopic analysis and pigment taxonomy suggested that phytoplankton community structure in the Laizhou Bay changed clearly, with the dominant community shifting from diatoms alone to the co-dominance of diatoms and cyanobacteria. Chaetoceros curvisetus, Skeletonema costatum, and Cerataulina pelagica, which were commonly observed in the Laizhou Bay before pollution control of the Xiaoqing River, decreased in 2018, whereas the abundance of common dominant freshwater species (e.g., Merismopedia sp. and Synedra spp.) increased significantly. Redundancy analysis (RDA) showed that the phytoplankton community was significantly related to nitrogen, phosphate (negative correlation), and salinity (negative correlation) after pollution control of the Xiaoqing River, indicating that the variation in nutrient concentration and the structure of river runoff input may be the main factors affecting phytoplankton community and dominant species structure.

Nutritional Quality and Safety of the Spirulina Dietary Supplements Sold on the Slovenian Market.

The microalgae Spirulina may be a popular dietary supplement rich in essential nutrients and vitamins, but oversight of the supplement industry, in general, remains limited, and increasing incidents of adulteration, misbranding, and undeclared ingredients together with misleading claims create potential risks. In response, this study characterized the elemental, amino acid and fatty acid content of commercially available Spirulina supplements in Slovenia using EDXRF, ICP-MS and GC-MS and compared the results with their nutritional declaration. The gathered data confirm that Spirulina supplements are a good source of calcium (0.15 to 29.5% of RDA), phosphorous (3.36–26.7% of RDA), potassium (0.5 to 7.69% of RDA) and selenium (0.01 to 38.6% of RDA) when consumed within recommended amounts. However, although iron contents were relatively high (7.64 to 316% of RDA), the actual bioavailability of iron was much lower since it was mainly present as the ferric cation. This study also confirms that pure Spirulina supplements are a good source of essential and non-essential amino acids, and ω-6 but not ω-3 polyunsaturated fatty acids. The presence of additives resulted in significant variation in nutrient content and, in some instances, lower product quality. Moreover, a high proportion (86.7%) of inappropriate declarations regarding the elemental content was observed. Overall, the study conclusions underline the need for a stricter control system for Spirulina-based supplements.

Land Use and Land Cover Shape River Water Quality at a Continental Caribbean Land-Ocean Interface

Land use and land cover (LULC) can significantly alter river water, which can in turn have important impacts on downstream coastal ecosystems by delivering nutrients that promote marine eutrophication and hypoxia. Well-documented in temperate systems, less is known about the way land cover relates to water quality in low-lying coastal zones in the tropics. Here we evaluate the catchment LULC and the physical and chemical characteristics of six rivers that contribute flow into a seasonally hypoxic tropical bay in Bocas del Toro, Panama. From July 2019 to March 2020, we routinely surveyed eight physical and chemical characteristics (temperature, specific conductivity, salinity, pH, dissolved oxygen (DO), nitrate and nitrite, ammonium, and phosphate). Our goals were to determine how these physical and chemical characteristics of the rivers reflect the LULC, to compare the water quality of the focal rivers to rivers across Panama, and to discuss the potential impacts of river discharge in the Bay. Overall, we found that the six focal rivers have significantly different river water characteristics that can be linked to catchment LULC and that water quality of rivers 10 s of kilometers apart could differ drastically. Two focal catchments dominated by pristine peat swamp vegetation in San San Pond Sak, showed characteristics typical of blackwater rivers, with low pH, dissolved oxygen, and nutrients. The remaining four catchments were largely mountainous with >50% forest cover. In these rivers, variation in nutrient concentrations were associated with percent urbanization. Comparisons across Panamanian rivers covered in a national survey to our focal rivers shows that saltwater intrusions and low DO of coastal swamp rivers may result in their classification by a standardized water quality index as having slightly contaminated water quality, despite this being their natural state. Examination of deforestation over the last 20 years, show that changes were <10% in the focal catchments, were larger in the small mountainous catchments and suggest that in the past 20 years the physical and chemical characteristics of river water that contributes to Almirante Bay may have shifted slightly in response to these moderate land use changes. (See supplementary information for Spanish-language abstract).

Studies on Mineral Nutrient Concentration of different Cultivars of Sweet Cherry (Prunus avium L.) in Kashmir

The aim of the study was to investigate the differences in leaf nutrient concentrations among the three cultivars (Misri, Double and Makhmali) of Sweet Cherry even though they are grown in same conditions. The other goal of the study was to determine variation in nutrient concentration of sweet cherry grown under different locations. Significant differences between cultivars were observed in nitrogen, calcium, Magnesium and Sulphur content in leaves, whereas phosphorus and potassium contents did not exhibit significant differences among the cultivars under study. The higher Nitrogen content was observed in Double and lowest in Makhmali cultivar. Higher content of Magnesium and Sulphur content was observed in Misri and lowest in Makhmali cultivar of sweet Cherry. All the macronutrients under study were significantly affected by the location of the orchards.

Phylloplane Biodiversity and Activity in the City at Different Distances from the Traffic Pollution Source.

The phylloplane is an integrated part of green infrastructure which interacts with plant health. Taxonomic characterization of the phylloplane with the aim to link it to ecosystem functioning under anthropogenic pressure is not sufficient because only active microorganisms drive biochemical processes. Activity of the phylloplane remains largely overlooked. We aimed to study the interactions among the biological characteristics of the phylloplane: taxonomic diversity, functional diversity and activity, and the pollution grade. Leaves of Betula pendula were sampled in Moscow at increasing distances from the road. For determination of phylloplane activity and functional diversity, a MicroResp tool was utilized. Taxonomic diversity of the phylloplane was assessed with a combination of microorganism cultivation and molecular techniques. Increase of anthropogenic load resulted in higher microbial respiration and lower DNA amount, which could be viewed as relative inefficiency of phylloplane functioning in comparison to less contaminated areas. Taxonomic diversity declined with road vicinity, similar to the functional diversity pattern. The content of Zn in leaf dust better explained the variation in phylloplane activity and the amount of DNA. Functional diversity was linked to variation in nutrient content. The fraction of pathogenic fungi of the phylloplane was not correlated with any of the studied elements, while it was significantly high at the roadsides. The bacterial classes Gammaproteobacteria and Cytophagia, as well as the Dothideomycetes class of fungi, are exposed to the maximal effect of distance from the highway. This study demonstrated the sensitivity of the phylloplane to road vicinity, which combines the effects of contaminants (mainly Zn according to this study) and potential stressful air microclimatic conditions (e.g., low relative air humidity, high temperature, and UV level). Microbial activity and taxonomic diversity of the phylloplane could be considered as an additional tool for bioindication.

Significant Temporal and Spatial Variability in Nutrient Concentrations in a Chinese Eutrophic Shallow Lake and Its Major Tributaries

Sediment nutrients can be released to the surface water when hydraulic disturbance becomes strong in shallow lakes, which contributes to nutrient enrichment and subsequent lake eutrophication in the water column. To explore the seasonal variations and spatial distributions exhibited by nutrients in the water column, surface sediment, and pore water of Lake Yangcheng and its major tributaries, we determined the concentrations of nitrogen (N) and phosphorus (P) throughout the lake in different seasons of 2018. Total N (TN) and total P (TP) concentrations in the connected rivers were much greater than those in the lake, indicating that external loading greatly contributed to the nutrient enrichment. TN concentration in the water column was highest in the winter, whereas TP peaked in the summer. A similar temporal pattern was observed for TN and TP in the sediment with maxima in the winter and minima in the summer; however, nutrients in the pore water were highest in the summer, in contrast to the temporal variation in the sediment. Additionally, high TN values in the water column and high TP in the three compartments were distributed primarily in the west part of the lake, while high TN concentrations in the sediment and pore water were observed mainly in the east portion of the lake. According to the enrichment factor index (an indicator evaluating the nutrient enrichment by comparing the detected contents and standard values), nutrients in the lake sediment were severely enriched with TN and TP averaging 2195.8 mg/kg and 543.0 mg/kg, respectively. The vertical distribution of TN and TP generally exhibited similar decreasing patterns with an increase in sediment depth, suggesting mineralization of TN and TP by microbes and benthic organisms. More attention and research are needed to understand the seasonality of nutrient exchange across the sediment–water interface, especially in eutrophic lakes.

Phytoplankton community structure is governed by salinity gradient and nutrient composition in the tropical estuarine system

Primary production in the estuarine ecosystems is principally represented by phytoplankton. The presence or function of phytoplankton in estuarine production is mainly regulated by factors such as salinity, light, turbidity, temperature, nutrients, grazers and the dynamics of the water basin. In order to understand the impact of salinity and hydrological characteristics on phytoplankton community structure in tropical estuaries, surface water samples for phytoplankton and biogeochemical parameters were collected from 26 estuaries along the Indian coast during non monsoon/no discharge period. Large spatial gradient in salinity was observed within the estuary (upper, middle and lower regions of estuary) from 2 to > 15 due to sea water intrusion through tidal currents. A higher concentration of suspended particulate matter (SPM) is observed in the lower estuarine regions, such as Tapti, and Narmada due to higher tidal amplitude. Higher phytoplankton biomass/abundances in upper estuarine region is associated with higher concentration of nutrients, and lower salinity whereas higher SPM, grazers and salinity is noticed associating with lower phytoplankton abundance in lower estuarine region. Phytoplankton community structure is found to vary significantly with reference to salinity as green algae and diatoms were dominated in the low saline upper estuary, diatoms and blue-green algae were abundant in the moderate saline region of middle estuary and diatoms alone were prominent in the high saline lower estuarine region. Moreover, diatoms in the upper estuarine region is exhibiting high heterogeneity with Melosira spp., Thalassiosira spp., Navicula spp. and Nitzschia spp. while the middle estuary and lower estuary were homogenous, mainly dominated by Thalassiosira spp. Higher species diversity (lower species dominance) was observed in upper estuary due to the diverse taxa of green algae and blue-green algae along with diatoms, whereas lower diversity was noticed in the lower estuarine region. Present study reveals that availability of light and grazing pressure is predominately governing phytoplankton abundance, while variations in nutrient concentrations and salinity is more influencing phytoplankton community structure.

USE OF DIGITAL IMAGES TO CLASSIFY LEAF PHOSPHORUS CONTENT IN GRAPE TOMATOES

Leaf chemical analysis is one of the ways to assess plant development. However, this type of assessment is expensive and time-consuming. The variation of nutrient content in the leaves modifies the proportion of light reflected and absorbed by plants at different wavelengths. Being able to relate the color reflected by the leaves with their phosphorus (P) content and using this data as input into an artificial neural network (ANN) can be an alternative for its determination. For this, it is necessary to establish which colors are most correlated with the different nutrients. Therefore, the phosphorus content in tomato leaves was evaluated in this study, according to four treatments (0.25, 50, 75, and 100% of the P doses). Different vegetation indices were also evaluated using images of mini-tomato leaves through a principal component analysis to determine which ones would be suitable to serve as an input to an ANN (multilayer perceptron). DGCI (Dark Green Color Index) and Bn (Normalized Blue) were the indices most related to P content. The neural network obtained 90% accuracy in the classification after training using both sides of the leaves.

Impact of Variation in Nutrient Concentration on Ecosystem, Biomass, and Production in a Semi-enclosed Embayment: Osaka Bay

海域の全窒素 (TN) ・溶存無機態窒素 (DIN) が大きく低下した大阪湾において, 生態系の栄養段階ごとに生物量の経年変化および季節変動パターンの変化を調べた。調査期間の1990～2019年には, 経年的水温上昇はほとんどなかった。DINの低下に伴って, 一次生産量が減り, クロロフィルで測った植物プランクトン量が減り, これが繊毛虫・カイアシ類などの動物プランクトンの減少, 仔稚魚量の減少へと連動していた。生態系全体としては, 各栄養段階の現存量がほぼ線形的に応答するボトムアップのシステムとなっていた。TNの低下が, DINの枯渇期間を夏のみから, 春から夏に広げ, これによる一次生産量の低下が, 上位栄養段階への窒素フローを減らしたと考えられた。また, 仔稚魚では, 内湾性魚種はどの優占魚種も生物量が大きく減少していた。一方, 広域回遊性のカタクチイワシだけは減らず, この一種のみが優占する状態に変化していた。

Determinação da folha padrão para diagnóstico nutricional do Açaizeiro

Abstract Assai palm is the main palm tree grown in the Brazilian Amazon. Nutritional diagnosis has become an essential tool in management of the crop. The aim of this study was to determine the standard leaf for nutritional diagnosis of the assai palm tree through evaluation of leaf nutrient content and use of two methods of statistical analyses: traditional (univariate) and multivariate. The study was conducted in the municipality of Belém, with eight treatments: the phyllotaxic positions of the leaves (number 2 to 9), in a completely randomized design. The leaf concentration of nutrients (N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn) was determined for performing descriptive analyses, analyses of variance, correlation analysis, and principal component analysis (PCA). Young leaves had greater concentrations of N, P, K, Mg, S, Cu, and Zn, whereas in the older leaves, there were greater concentrations of Ca, B, Fe, and Mn. The leaves that exhibited less variation in nutrient concentrations were from 2 to 5. PCA analysis indicated interaction of positive loads of N-P and Cu-Mg and interaction of negative loads of Ca-Mn. The index of nutrient distribution indicated leaf number 5 as having the lowest factor loading value. Thus, leaf number 5 is most recommended for nutritional diagnosis of assai palm plants through sampling of 25 plants.

The Growth of Chlorella sp. With Varying Nutrient Concentration

The aim of this study was to determine the effect of differences addition of culture medium concentrations on the growth of microalgae type Chlorella sp. Samples were obtained from the Center for Brackish Water Cultivation Fisheries (BBPBAP), Jepara. This research was conducted at the Laboratory of Nutrition and Natural Feed Sorong Marine and Fisheries Polytechnic with an experimental method using four treatments with addition of walne medium, there were A (adding only at the beginning of cultivation); treatment B (adding every day); C (adding every two days), and treatment; D (adding every three days). The cell growth performance was significantly found in treatment C with the addition of nutrients every two days with a peak cell density of Chlorella sp was 2,628,450 cells / ml. There is a need for mass culture assay to determine the level of effectiveness and efficiency.

A Research Method for Semi-Automated Large-Scale Cultivation of Maize to Full Maturity in an Artificial Environment

There are unique advantages and disadvantages to using the field, greenhouse, growth chamber, and media-less techniques for growing maize (Zea mays L.) for research purposes. Soil-buffered nutrients such as phosphorus (P) do not allow for precise control of solution concentrations in the field, while greenhouses, growth chambers, and hydroponics provide limiting conditions. The objectives of this study were to develop a practical technique for productively cultivating several maize plants from seed to physiological maturity (R6) in a grow room environment, with precise control of nutrient availability and timing, and evaluate its utility for the purpose of measuring plant responses to variations in nutrient concentrations. The construction and testing of a semi-automated grow room for conducting nutrient studies on 96 maize plants utilizing simulated or artificial conditions are described. Plant growth response to a range of solution phosphorus (P) concentrations was tested to evaluate the utility of the technique. Maize yield components were measured and compared to values for field-grown plants. Due to ideal conditions and successful simulation of light intensity, diurnal fluctuations in temperature and RH, and changing photoperiod, grain yield and tissue nutrient concentrations were comparable to field-grown maize, although with greater shoot biomass. Plants responded positively to increased P concentrations in fertigation. The technique can be used for large-scale plant nutrient studies that require precise control of bioavailability and timing as well as manipulation of light intensity and photoperiod duration.

Estimation of Populuseuphratica Forest Leaf Litterfall and Time Variation of Nutrient in Leaf Litter during Decomposition along the Main Channel of the Tarim River, China

Accurate determination of annual leaf litter amount constitutes the basis of scientific leaf litter nutrient release assessment. In this study, we tried to establish an equation between leaf litter amount and relevant tree characteristics of Populus euphratica (P. euphratica) tree on an individual scale, and to find the leaf litter nutrient content variation within 760 d incubation experiment in the main channel of the Tarim River, China. Results showed that there was no proper equation between leaf litter amount and tree height or diameter at breast height. There was great difference in leaf litter amount on an individual scale. The mean annual leaf litter amount per tree was 10.2, 14.83 kg/y obtained by field survey and the equation between annual leaf litter amount and canopy area on an individual scale, respectively. Leaf litter mass changed over incubation time and exhibited three main phases: an initial slow decomposition phase (0–173 d) with mass loss; a rapid mass loss phase (173–290 d); and a second rapid mass loss phase (470–560 d). Overall, carbon (C) and potassium (K) content decreased, and nitrogen (N) and phosphorus (P) content increased in a fluctuating manner over time in the P. euphratica leaf litter.

Influence of Nutrient Manipulation on Growth and Biochemical Constituent in Anabaena variabilis and Nostoc muscorum to Enhance Biodiesel Production

The present study aims to improve biomass and biochemical constituents, especially lipid production of Anabaena variabilis and Nostoc muscorum by formulating an optimal growth condition using various concentrations of nutrients (NO3−, PO43− and CO32−) for biodiesel production. The supplementation of the three nutrients by +50% showed the maximum dry weight and biomass productivity, while the macromolecule contents were varied. The depletion of N-NO3− by 50% N-NO3− showed the maximum lipid yield (146.67 mg L−1) in A. variabilis and the maximum carbohydrate contents (285.33 mg L−1) in N. muscorum with an increase of 35% and 30% over control of the synthetic medium, respectively. However, variation in P-PO43− and C-CO32− showed insignificant improving results for all biochemical compositions in both cyanobacteria. A. variabilis was the superior species for lipid and protein accumulation; however, N. muscorum showed the maximum carbohydrate content. Accordingly, A. variabilis was selected for biodiesel production. In A. variabilis, −50% N-NO3− resulted in 35% higher lipid productivity compared to the control. Furthermore, the fatty acid profile and biodiesel quality-related parameters have improved under this condition. This study has revealed the strategies to improve A. variabilis lipid productivity for biodiesel production for small-scale in vitro application in terms of fuel quality under low nitrate levels.

Seasonal variations of nutrient concentrations and their ratios in the central Bohai Sea

The Bohai Sea is a typical semi-enclosed sea in the northwest Pacific, which is subject to serious eutrophication due to human activities. Similar to hydrographic variables such as water temperature and salinity, the nutrient concentrations and ratios in the Bohai Sea also exhibit seasonal variations. However, the effects of external inputs, biological processes, and benthic processes on these seasonal variations have not been quantified to date. To address this issue, a physical–biological coupled model was developed to capture the seasonal nutrient cycling in the central Bohai Sea. The simulation results revealed apparent seasonal variations in the concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and dissolved silicate (DSi). The N/P ratio (as the molar ratio of DIN/DIP) also exhibited an apparent seasonal variation, with the maximum and minimum values in surface water occurring in summer (>100) and winter (<30), respectively. The Si/N ratio (as the molar ratio of DSi/DIN) was slightly higher in summer than in other seasons. The budget for three types of nutrient indicated that the biological processes determined the seasonal variations in nutrient concentrations and the N/P ratio. The external inputs of nutrients via river input, atmospheric deposition, and sediment release were probably important in summer when they could alleviate the reduced nutrient concentrations due to biological processes. To maintain a reasonable nitrogen budget, it was necessary to include benthic nitrogen loss, which removed a large amount of inorganic nitrogen in summer and autumn. In addition, the variation of N/P ratio of phytoplankton uptake can reduce the ratio of DIN to DIP in surface water by ~20 in summer as compared to the calculation with a fixed N/P ratio (16:1) in phytoplankton uptake.

Comparing spiraling‐ and transport‐based approaches to estimate in‐stream nutrient uptake length from pulse additions

AbstractThe distance that a nutrient travels as a solute before its removal from the stream water column is known as the uptake length (SW), which is a functional indicator of environmental quality and integrity. Among nutrient enrichment methods, instantaneous nutrient addition (e.g., slug or pulse) have been proposed as an alternative to plateau and labeled nutrient approaches. Two approaches have been commonly used to estimate SW and its associated metrics (i.e., areal uptake rate, U; and uptake velocity, Vf) from pulse additions: the spiraling approach, based on the longitudinal variation in nutrient concentrations, and the transport modeling approach, based on the advective and dispersive transport of solutes. However, little is known in how the choice of such analytical methods impacts the estimation of stream uptake parameters and the conclusions we draw from them. Here, we estimated the SW and Vf of ammonium‐nitrogen (NH4‐N) and soluble reactive phosphorus (SRP) from 16 pulsed additions conducted in four low‐order streams in southeastern Brazil. We compared metrics estimated by the Tracer Additions for Spiraling Curve Characterization (TASCC) and the One‐Dimensional Transport with Inflow and Storage (OTIS) methods, based on the spiraling‐ and transport‐based approaches, respectively. The TASCC:OTIS SW ratio averaged 0.71 for NH4‐N and 1.01 for SRP, whereas the mean of TASCC:OTIS Vf ratio was 2.04 for NH4‐N and 1.03 for SRP. The results showed that both SW and Vf estimates differed significantly between methods for NH4‐N, but no statistical differences were observed in SRP estimates. In our study, we highlighted the significant effects of transient storage and variable nutrient concentration on pulsed enrichments. Such information should be considered when choosing which method is appropriate to use for a particular site. Differences between modeling approaches must be addressed when comparing methods to expand our knowledge on broad temporal and spatial patterns of in‐stream nutrient uptake.

Neogene calcareous nannofossil biostratigraphy of the northern Indian Ocean: Implications for palaeoceanography and palaeoecology

Neogene sediments of the Andaman and Nicobar Islands in northern Indian Ocean, specifically the lower Miocene (Burdigalian) to lower Pliocene (Zanclean) sequences, were analysed for calcareous nannofossils that yielded well-preserved and diverse assemblages. The majority of samples contained stratigraphic marker taxa that allowed us to identify successions within the Burdigalian-Langhian (uppermost lower Miocene to lowermost middle Miocene) on the Havelock Island, Tortonian (upper Miocene) on the Neil Island and Zanclean (lower Pliocene) on the Car Nicobar Island. The nannofossil assemblages of uppermost lower Miocene to lowermost middle Miocene sediments reflect strong preference for warm tropical climate and nutricline condition i.e., depth dependent high variation of nutrient content. The presence of relatively unusual assemblage compositions, especially the presence of abundant sphenoliths and small reticulofenestrids, in conjunction with rare discoasters and alongside common diatoms, are indicative of high-productivity surface waters and probably upwelling conditions in the late Miocene. In the Tortonian (upper Miocene), low abundance of discoasters and high abundance of small reticulofenestrids (<3 μm) indicate eutrophic condition. The high-productivity surface-water environments can be linked with the intensification of the Indian Summer Monsoon. Well-preserved calcareous nannofossils have been also been recovered from the Zanclean (lower Pliocene) sediments on Car Nicobar Island. During the Zanclean warm water condition prevailed and from marginal to deep water setting i.e., transgressive event was recognised in the northern Indian Ocean.

Nutrient Deficiency Promotes the Entry of Helicobacter pylori Cells into Candida Yeast Cells.

Simple SummaryHelicobacter pylori is a pathogenic bacterium which causes several gastric and extra-gastric pathologies in humans. This pathogen is capable of entering eukaryotic cells of humans or of other species, including yeasts of the genus Candida. These yeasts are resistant to stressing environmental conditions (such as pH changes or scarce nutrients) which threaten the viability of H. pylori. Therefore, Candida yeasts may harbor this bacterium when subjected to stressing conditions or become transmission vehicles for it. Further research is required to establish the stressing environmental factors triggering the harboring of H. pylori within yeasts. The present work evaluated if deficiency or absence of the necessary nutrients favors the endosymbiotic relationship between these two microorganisms, facilitating the viability of the bacterium. In fact, a deficiency of nutrients increased the harboring of viable H. pylori cells within the yeast cells. On the contrary, in the complete absence of nutrients, the presence of intra-yeast bacteria was reduced. Therefore, yeast cells may contribute to the subsistence of this pathogenic bacterium when subjected to nutrient deficiency until it may infect an appropriate host, such as humans. The present work may also contribute, with further studies, to elucidate the transmission routes used by the pathogen H. pylori to infect its hosts.Helicobacter pylori, a Gram-negative bacterium, has as a natural niche the human gastric epithelium. This pathogen has been reported to enter into Candida yeast cells; however, factors triggering this endosymbiotic relationship remain unknown. The aim of this work was to evaluate in vitro if variations in nutrient concentration in the cultured medium trigger the internalization of H. pylori within Candida cells. We used H. pylori–Candida co-cultures in Brucella broth supplemented with 1%, 5% or 20% fetal bovine serum or in saline solution. Intra-yeast bacteria-like bodies (BLBs) were observed using optical microscopy, while intra-yeast BLBs were identified as H. pylori using FISH and PCR techniques. Intra-yeast H. pylori (BLBs) viability was confirmed using the LIVE/DEAD BacLight Bacterial Viability kit. Intra-yeast H. pylori was present in all combinations of bacteria–yeast strains co-cultured. However, the percentages of yeast cells harboring bacteria (Y-BLBs) varied according to nutrient concentrations and also were strain-dependent. In conclusion, reduced nutrients stresses H. pylori, promoting its entry into Candida cells. The starvation of both H. pylori and Candida strains reduced the percentages of Y-BLBs, suggesting that starving yeast cells may be less capable of harboring stressed H. pylori cells. Moreover, the endosymbiotic relationship between H. pylori and Candida is dependent on the strains co-cultured.