Function Of Nutrient Concentration Research Articles

Temporal distribution of primary and secondary production estimated from water quality data in the Seto Inland Sea, Japan

Estuaries and coastal areas support highly productive fisheries and aquaculture operations. The high productivity is partly supported by inputs of nutrients from land; consequently, these areas are sensitive and vulnerable to human activities. Excess anthropogenic nutrient input can lead to accelerated phytoplankton growth and associated environmental problems. Good management practices are needed to achieve high productivity and healthy environmental conditions simultaneously. This requires close monitoring of environmental conditions and productivity, especially at lower trophic levels. Although environmental conditions, especially water quality, are widely monitored, primary production (PP) and secondary production (SP) are rarely monitored even though these basic parameters govern the structure and functioning of marine ecosystems. In this study, we developed methods to estimate PP and the SP from commonly collected water quality indicators and without the use of any information on phytoplankton or zooplankton except chlorophyll a (Chl.a) concentration. For this purpose, we developed the method to determine the half-saturation constants as a function of nutrient concentration, and the method to determine the SP from Chl.a concentration. Then, we used our newly developed methods to estimate the temporal distribution of PP and SP in the Seto Inland Sea from the 1980s to the present. To do so, we monitored water quality at three sites with different levels of eutrophication. We also measured PP by using 13C-labeled sodium bicarbonate (NaH13CO3) incubation method, and calculated copepod SP based on the species and body size of copepods collected in a survey. To estimate PP from water quality data, we modeled PP using a half-saturation constant for nutrient uptake that was allowed to vary as a function of nutrient concentration. Seasonal differences in PP could be successfully estimated by using this method. The estimation error for PP was within −16% to 23%. We found that SP calculated from copepod species and body size data was significantly correlated with chlorophyll a concentration. Therefore, we proposed a model to estimate SP from chlorophyll a concentration. Then, we used our newly developed models to estimate the temporal distribution of both PP and SP in the Seto Inland Sea from seasonal water quality data. According to our estimates, annual mean PP and SP peaked in the late 1990s and have trended downward since around 2000 or 2005. No significant inter-decadal changes in autumn or winter PP were observed during our study period; by contrast, spring and summer PP decreased significantly from the 1990s to the present. Estimated annual mean PP and SP over the most recent 5-year period were 73% and 88%, respectively, of equivalent values estimated for the 1990s.

Phytoplankton size- and abundance-based resilience assessments reveal nutrient rather than water level effects

The use of discontinuity analysis to assess resilience and alternative regimes of ecosystems has mostly been based on animal size. We so far lack systematic comparisons of size-based and abundance-based approaches necessary for assessing the performance and suitability of the discontinuity analysis across a broader range of organism groups. We used an outdoor mesocosm setup to mimic shallow lake ecosystems with different depths (1.2 m deep, “shallow”; 2.2 m deep, “deep”) and trophic status (i.e. low and high nutrient status characteristic of mesotrophic and hypertrophic lakes, respectively). We compared resilience assessments, based on four indicators (cross-scale structure, within-scale structure, aggregation length and gap size) inferred from the size and abundance (biovolume) structure of phytoplankton communities. Our results indicate that resilience assessments based on size and biovolume were largely comparable, which is likely related to similar variability in the size and abundance of phytoplankton as a function of nutrient concentrations. Also, nutrient enrichment rather than water depth influenced resilience, manifested in decreased cross-scale structure and increased aggregation lengths and gap sizes in the high-nutrient treatment. These resilience patterns coupled with decreased phytoplankton diversity and dominance of cyanobacteria in the high nutrient treatment support the use of discontinuity analysis for testing alternative regimes theory. Concordance of size-based and abundance-based results highlights the approach as being potentially robust to infer resilience in organism groups that lack discrete size structures.

Removal of tetracycline and ciprofloxacin from wastewater by vetiver grass (Chrysopogon zizanioides (L.) Roberty) as a function of nutrient concentrations.

Antibiotics have been widely used not only for the treatment and prevention of human infectious diseases but also to promote growth and prevent infections in farm animals. These antibiotics enter the environment via wastewater treatment plants, most of which cannot remove them. In addition to antibiotics, nutrients such as nitrogen (N) and phosphorus (P) also create major environmental pollution problems in surface water. Previously, we reported that vetiver grass [Chrysopogon zizanioides (L.) Roberty] successfully removed antibiotics from secondary wastewater effluent. In this study, our objective was to evaluate the potential of vetiver grass to remove two antibiotics, ciprofloxacin (CIP) and tetracycline (TTC), from wastewater in the presence of high N and P. Our results show that vetiver grass significantly (p < 0.05) removed antibiotics (60-94% CIP and 89-100% TTC) and nutrients (78-89% N and 71-97% P) from the secondary wastewater effluent. The removal of antibiotics dropped with increasing nutrient concentrations. The removal efficiency was mainly affected by the presence of N rather than P in the secondary wastewater effluent. The presence of CIP induced more stress on vetiver grass compared to TTC. Vetiver also removed total organic carbon (48-73%) and chemical oxygen demand (73-82%), but their removal was also affected by the nutrient content in the secondary wastewater effluent.

Comparison of the effects of metformin on MDA-MB-231 breast cancer cells in a monolayer culture and in tumor spheroids as a function of nutrient concentrations

Metabolic pathways of cancer cells depend on the concentrations of nutrients in their micro-environment as well as on the cell-to-cell interactions. Here we examined the effects of glucose, pyruvate and glutamine on the sensitivity of MDA-MB-231 cells to metabolic drug metformin using standard 2D culture, in which cells are grown in a monolayer, and 3D tumor spheroids, in which three-dimensional growth of cells better mimics a tumor. To examine effects of nutrients on metformin action, MDA-MB-231 cells were grown in commonly used media (DMEM, MEM and RPMI-1640) that differ mainly in the concentrations of amino acids. We used MTS assay and Hoechst and propidium iodide staining to determine cell number, viability and survival, respectively. We also determined the size of tumor spheroids and assessed effects of nutrients on metformin-stimulated AMP-activated protein kinase activation. Non-essential amino acids suppressed the effects of metformin on MDA-MB-231 cells in a 2D culture and in 3D tumor spheroids. Glutamine and pyruvate weakly diminished the effects of metformin in 2D culture. Furthermore, glucose protected tumor spheroids against metformin-induced disintegration. Our results show that nutrient availability must be considered when we evaluate the effects of metformin in 2D culture and in biologically more relevant 3D tumor spheroids.

Tolerance towards gentamicin is a function of nutrient concentration in biofilms of patient-isolated Staphylococcus epidermidis

Staphylococcus epidermidis is a biofilm-forming bacterial strain that can cause major problems as an agent of nosocomial infections. Bacteria in biofilms are shielded from the environment and can survive high doses of antibiotics. We here test the antibiotic susceptibility of Staphylococcus epidermidis to rising gentamicin concentrations in optimal growth conditions as used in routine bacteriology laboratories with low nutrient situations as suggested to be found in clinical situations. We found that gentamicin-resistant Staphylococcus epidermidis biofilms survived in the absence of external nutrient supply in PBS. While addition of gentamicin sulfate significantly reduced the pH value of all used media and solutions, this acidification did not alter survival of bacteria in the biofilm. We found a statistically significant and dose-dependent reduction of survival in low nutrient situations using gentamicin sulfate in three out of four patient isolates of Staphylococcus epidermidis which have been tested to be gentamicin-resistant under optimal growth conditions. Supporting the original profiling, survival in full media under the same antibiotic dosages was not significantly reduced. Our data here show that antibiotic resistance is a function of the provided nutrient concentration. Antibiotic resistance profiling should consider variations in nutrient availability.

Flexible phytoplankton functional type (FlexPFT) model: size-scaling of traits and optimal growth

Recent studies have analysed valuable compilations of data for the size-scaling of phytoplankton traits, but these cannot be employed directly in most large-scale modelling studies, which typically do not explicitly resolve the relevant trait values. Although some recent large-scale modelling studies resolve species composition and sorting within communities, most do not account for the observed flexible response of phytoplankton communities, such as the dynamic acclimation often observed in laboratory experiments. In order to derive a simple yet flexible model of phytoplankton growth that can be useful for a wide variety of ocean modelling applications, we combine two trade-offs, one for growth and the other for nutrient uptake, under the optimality assumption, i.e. that intracellular resources are dynamically allocated to maximize growth rate. This yields an explicit equation for growth as a function of nutrient concentration and daily averaged irradiance. We furthermore show how with this model effective Monod parameter values depend on both the underlying trait values and environmental conditions. We apply this new model to two contrasting time-series observation sites, including idealized simulations of size diversity. The flexible model responds differently compared with an inflexible control, suggesting that acclimation by individual species could impact models of plankton diversity.

Modelling of Impact of Detritus on Detritivorous Food Chain of Sundarban Mangrove Ecosystem, India

b Institute of Environmental Studies and Wetland Management, B-4 Sec-III, LA-Block, Saltlake City, Kolkata 700 098, India. Abstract Decomposition and subsequent remineralization of mangrove detritus is important in nutrient dynamics within the forest as well as in offshore system. In order to study the impact of detritivorous fish on the mangrove estuarine detritus food web, a five compartment model of detritus food web dynamics has been developed for mangrove estuarine creeks of Hooghly- Matla Estuarine complex, Sundarban. The model simulates concentration of nutrient, biomass of phytoplankton, zooplankton, detritus and detritivorous fishes. Almost 70% of the detritus formed in the soil was being washed in the estuarine water to act as source or sink of nutrient for the primary producers of aquatic food chain. A significant amount of detritus in the estuarine water is readily consumed by a group of detritivorous fishes before it is being rematerialized completely in to inorganic nutrient form. The model has been calibrated and validated using field data accordingly. Increased detrital nitrogen values in the late monsoon and post monsoon months, assists the growth and high yield of detritivorous fishes as found in simulated and field observations. Comparison of simulated and observed results demonstrates the dependence of phytoplankton growth is a function of nutrient concentration and zooplankton grazing. Model results also show the dependence of detritivorous fishes on detritus which is a function of detritus biomass. In turn, detritus biomass is dependent upon several factors like mortality of phytoplankton, zooplankton, and detritivorous fishes; and chiefly on litter biomass and litter decomposition.

History of reference materials for food and nutrition metrology: as represented in the series of BERM symposia

FigureUncertainty interval percentages (UIP) in certified reference materials as a function of nutrient concentration. P proximates, C carbohydrates, M minerals, T trace elements, VS water soluble vitamins, VF fat-soluble vitamins, A amino acids, F fatty acids, O other[IMAGE]

Potamoplankton size structure and taxonomic composition: Influence of river size and nutrient concentrations

We measured the size structure and taxonomic composition of phytoplankton in temperate rivers during base flows of summer to investigate the influence of river size, ambient nutrient concentration, and light availability on potamoplankton community structure. Algal biomass was measured in three size classes (2–20, 20–64, and &gt;64 µm) by microscope enumeration of water samples collected in 31 rivers and by chlorophyll a in water samples collected in 46 rivers in another year across Ontario and western Quebec. Nanoplankton dominated the potamoplankton biomass across the range of river nutrient concentrations (total phosphorus 5–280 µg P L−1), water residence times (1–39 d), and light regimes (euphotic zone to mixing depth ratio 0.1–33). Both nanoplankton (2–20 µm) and total potamoplankton biomass were significantly correlated with water column total phosphorus concentrations and were not related to water residence time or light availability. On average, diatoms contributed the largest percentage of the total biomass, followed by cryptophytes and an equal percentage of chlorophytes and chrysophytes. The contribution of any one division to total biomass was not significantly correlated with nutrients, water residence time, or light regime. In contrast to temperate lake systems, both the proportion of biomass in larger size classes and the contribution of cyanobacteria did not change significantly as a function of nutrient concentrations. However, community size structure varied in relation to river size: netplankton (&gt;64 µm) contributed slightly more to total biomass at sites with both shorter (&lt;2 d) and longer (&gt;10 d) water residence times. These results point to differences between the phytoplankton of lakes and rivers in response to eutrophication.

Nutrient uptake, chlorophyll a and carbon fixation by Rhodomonas sp. (Cryptophyceae) cultured at different irradiance and nutrient concentrations

The goal of this research was to study biomass production, nitrate and phosphate uptake and carbon fixation in batch culture of the marine microalgae Rhodomonas sp., which is used in aquaculture as food for commercially reared invertebrates. Cultures were grown for 7 days under four irradiance levels (52, 68, 103 and 142μmolphotonm−2s−1) and at three nitrate and phosphate concentrations (661–29, 882–39, 1323–58.5μM of NaNO3 and NaH2PO4, respectively) establishing 12 experimental treatments. During the exponential phase, growth was directly correlated with irradiance and the initial nitrate and phosphate concentrations. Significant differences were found in the low growth phase as a function of nutrient concentration, but not for irradiance. For the low nutrient concentration treatments, growth was limited after 2 days. Final cell density was influenced by the initial concentration of nutrients, independently of the irradiance level. The average maximum biomass production was reached in 7 days in cultures with high nutrients (1.53±0.07×106cellsmL−1). The total chlorophyll a content was directly related to cellular density and indirectly to irradiance level and concentration of nutrients. In conclusion, the optimal growing condition for Rhodomonas was up to the fourth day. However, after this time the cellular density, chlorophyll content and carbon uptake changed with the nutrient concentration and irradiance. Therefore we suggest that Rhodomonas culture could be used at the fourth day, either as inoculums for higher volume or as nourishment for invertebrate animals in marine aquaculture program.

Sterilization‐in‐place of concentrated nutrient solutions

Sterilization-in-place (batch sterilization) behavior of concentrated nutrient solutions was quantified for various nutrient solutions of fermentation processing interest. Experimental observations of sterilization temperatures and corresponding pressures suggested that sterilization pressures were substantially lower for concentrated nutrient solutions than for water. This effect was believed to be directly related to the lower vapor pressure and lower activity coefficient of these concentrated nutrient solutions. Using thermodynamic data for the specific nutrient, pressures and temperatures, calculated as a function of nutrient concentration, compared favorably with observed values. This method permits estimation of the expected sterilization pressure for concentrated nutrients for which no experimental observations have yet been made at the sterilization temperature of interest. Estimate accuracy, ranging from 0.006 to 0.06 bar, can be enhanced if one set of experimental temperature/pressure values is known at the expected sterilization scale. The potential impact of the nature of concentrated nutrient solutions on steam-in-place vessel headspace temperature distributions, D-values of B. stearothermophilus, and overall sterilization effectiveness is also discussed. The low vapor pressure of concentrated nutrient solutions was hypothesized to directly impact air removal effectiveness and sterilization performance during batch sterilization. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62:501–508, 1999.

Sterilization-in-place of concentrated nutrient solutions

Sterilization-in-place (batch sterilization) behavior of concentrated nutrient solutions was quantified for various nutrient solutions of fermentation processing interest. Experimental observations of sterilization temperatures and corresponding pressures suggested that sterilization pressures were substantially lower for concentrated nutrient solutions than for water. This effect was believed to be directly related to the lower vapor pressure and lower activity coefficient of these concentrated nutrient solutions. Using thermodynamic data for the specific nutrient, pressures and temperatures, calculated as a function of nutrient concentration, compared favorably with observed values. This method permits estimation of the expected sterilization pressure for concentrated nutrients for which no experimental observations have yet been made at the sterilization temperature of interest. Estimate accuracy, ranging from 0.006 to 0.06 bar, can be enhanced if one set of experimental temperature/pressure values is known at the expected sterilization scale. The potential impact of the nature of concentrated nutrient solutions on steam-in-place vessel headspace temperature distributions, D-values of B. stearothermophilus, and overall sterilization effectiveness is also discussed. The low vapor pressure of concentrated nutrient solutions was hypothesized to directly impact air removal effectiveness and sterilization performance during batch sterilization. Copyright 1999 John Wiley & Sons, Inc.

Forage Quality for Ruminants: Plant and Animal Considerations

Forage quality is a function of nutrient concentration, intake, nutrient availability, and partitioning of metabolized products within animals. Of these factors, intake potential is the major determinant of production by animals fed forage-based diets; however, it is one of the most difficult aspects of forage quality to determine or predict because variation among animals has a large influence on intake. Physical fill limits intake of forages with high cell wall concentrations when fed to animals with high energy demand. Hence, grasses, with their higher cell wall concentration, typically have lower intake than legumes. Energy availability of forage is also limited by cell wall concentration because cell contents are almost completely digested, whereas forage cell walls are slowly digested. Thus, the proportion of cell walls to cell contents is a major determinant of energy availability in feeds. Protein digestion by ruminants is complex. When crude protein concentration in herbage drops below 7% of dry matter, ruminal fermentation of forages may be limited and protein requirements of animals may not be met. Additionally, inefficient use of protein in high quality forages may limit performance of high producing animals. Usually, only about 25% of the forage protein escapes degradation from the rumen. Efficiency would be improved if a larger portion of forage protein passed from the rumen undegraded so that it can be degraded in the intestines where absorption is more efficient. Another important plant factor influencing forage quality is herbage maturity. Systems are now available for determining maturity of both legumes and grasses that will become more important as aids for predicting forage quality before forages are harvested or grazed. Forage quality is also influenced by the environment in which forages are grown and by soil fertility and these cause year-to-year, seasonal, and geographical variation in forage quality even when herbage is harvested at the same stage of maturity.

Models on Nutrient Limitation of Uptake and Growth of Microalgae. Variability of Half-Saturation Constants.

Quantitative regulation of nutrient uptake by unicellular microalgae (phytoplankton) is the key physiological process that governs nutrient cycling and phytoplankton population dynamics in natural waters. Kinetic models are widely used in quantitative description of uptake and growth as functions of nutrient concentration. A review of both experimental and theoretical works on nitrogen and phosphorus uptake by cultured unicellular algae is presented here. At least three different values of half saturation constants are identified depending on the time scale of analysis, while a single system for ion transport is considered. Quantitative relationship is obtained theoretically and experimentally among these different values of half saturation constants.

Fish guts as chemical reactors: a model of the alimentary canals of marine herbivorous fishes

The alimentary canals of marine herbivorous fishes are variously composed of a few basic structures strung together in series. We model the structures where digestive processes occur as chemical reactors following the model of Penry and Jumars: the stomach as a batch or continuous-flow stirred-tank (CSTR), the intestine as a plug-flow reactor (PFR), and the hindgut caecum as a CSTR. Other structures, where food is mechanically processed-gill rakers, pharyngeal mills, and muscular stomachs-are classified as gates. The optimality criterion for the model is the digestion of the most nutrient in the least amount of time. With the model we are able to predict gut configuration as a function of nutrient concentration and hypothesize that the guts of herbivorous fishes always have a PFR component and may or may not have a CSTR component. The Penry-Jumars model appears to provide a consistent theoretical framework for four main types of digestive mechanisms in marine herbivorous fishes and offers specific testable hypotheses on the feeding ecology and digestive physiology of four representative species of fish as well as other, still unstudied, herbivorous fishes.

Periphyton biomass dynamics in gravel bed rivers: the relative effects of flows and nutrients

SUMMARY. 1. Periphyton chlorophyll a and ash free dry weight (AFDW) were monitored in nine rivers to examine the relative importance of flows and nutrients for regulating periphyton biomass in gravel bed rivers.2. Mean annual flows in the rivers ranged from 0.94 to 169 m3 s−1, mean dissolved reactive phophorus (DRP) from 1.3 to 68 μ g 1−1, periphytic chlorophyll a from 4.6 to 73 mg m −2. and AFDW from 2.8 to 16 g m−2.3. For eight of the nine rivers NH4‐N. DRP, total Kjeldahl nitrogen, total phosphorus and total suspended solids were correlated (P&lt;0.01) with flow, and for seven rivers conductivity was inversely correlated (P&lt;0.05) with flow.4. There was a hyperbolic relationship between flows and biomass, with chlorophyll a &gt;100 mg m −2 and AFDW &gt;20 g m−2 occurring most frequently in flows of &lt;20 m3 s−1.5. Floods prevented the development of medium term (i.e. up to 2 months) maxima in biomass in five of the rivers, but maxima occurred over summer‐autumn and winter‐spring in the three rivers where floods were absent.6. Chlorophyll a biomass was more resistant to flooding than AFDW. Only 5993 of the forty‐six recorded floods caused chlorophyll a scouring, whereas 74% of the floods caused AFDW scouring. The efficiency of scour was more influenced by the pre‐flood biomass than the magnitude of the event.7. Biomass maxima were significantly correlated (P&lt;0.01) with mean DRP concentration during the accrual period. Overall, up to 53% of the mean annual biomass difference between rivers was explained by the mean annual DRP concentrations. However, the high correlations between nutrient concentrations and flow indicated that the nutrient data were also carrying hydrological information and that simple causal relationships between nutrients and biomass are difficult to establish in rivers.8. It is concluded that hydrological factors contribute at least equally with nutrients to the differences in periphyton biomass between the gravel‐bed study rivers. They combined to explain up to 63.3% of the variance in biomass, compared with 57.6% for nutrients. It is recommended that periphyton data from gravel‐bed rivers should always be viewed within the context of the flow history of the site, and not just as a function of nutrient concentrations.