Nitrogen turnover rates in a riparian fen determined by 15N dilution

1992 ◽  
Vol 14 (4) ◽  
pp. 230-236 ◽  
Author(s):  
Per Ambus ◽  
Arvin Mosier ◽  
S�ren Christensen
Keyword(s):  
Turnover Rates ◽  
Nitrogen Turnover ◽  
15N Dilution

scholarly journals Isotopic discrimination factors and nitrogen turnover rates in reared Atlantic bluefin tuna larvae (Thunnus thynnus): effects of maternal transmission

2016 ◽  
Vol 80 (4) ◽  
pp. 447 ◽  
Author(s):  
Amaya Uriarte ◽  
Alberto García ◽  
Aurelio Ortega ◽  
Fernando De la Gándara ◽  
José Quintanilla ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Stable Isotope ◽  
Bluefin Tuna ◽  
Gilthead Seabream ◽  
Half Time ◽  
Turnover Rates ◽  
Thunnus Thynnus ◽  
Data Set ◽  
Nitrogen Turnover ◽  
Discrimination Factors

The use of stable isotope analysis to study animal diets requires estimates of isotopic turnover rates (half time, t50) and discrimination factors (Δ) for an accurate interpretation of trophic patterns. The stable isotopes of carbon and nitrogen were analysed for eggs and reared larvae of Thunnus thynnus, as well as for the different diets supplied during the experiment. The results showed high values of δ15N in eggs and larvae (n=646) until 4 DAH. After this time lapse, the stable isotope values declined progressively until 12 DAH, when notochord flexion began. The δ13C showed an inverse trend, suggesting that maternal inheritance of the stable isotopes is evident until pre-flexion stages. This study proposes a model for estimating maternal isotopic signatures of bluefin broodstock. After notochord flexion, larvae were fed with aquaculture-bred gilthead seabream, which resulted in a rapid increase of bluefin larvae δ15N values together with a rapid decrease in δ13C values. The estimated nitrogen half-time to reach the steady state from the diet was 2.5±0.3 days and the discrimination factor was 0.4±0.3(‰). These results represent the first data set that has allowed isotopic nitrogen turnover rates and discrimination factors of the larval stages of bluefin tuna to be estimated.

scholarly journals The distinct roles of two intertidal foraminiferal species in phytodetrital carbon and nitrogen fluxes – results from laboratory feeding experiments

2018 ◽  
Author(s):  
Julia Wukovits ◽  
Max Oberrauch ◽  
Annekatrin J. Enge ◽  
Petra Heinz
Keyword(s):  
Organic Matter ◽  
Food Source ◽  
Nitrogen Sources ◽  
Carbon Turnover ◽  
Turnover Rates ◽  
Short Term ◽  
Carbon And Nitrogen ◽  
Nitrogen Turnover ◽  
Feeding Experiments ◽  
Different Temperatures

Abstract. Benthic foraminifera play a major role as primary consumers and detrivores redistributing organic carbon and nitrogen in intertidal environments. Here we compared the differences of phytodetrital carbon and nitrogen intake and turnover of two dominant intertidal foraminifera, Ammonia tepida and Haynesina germanica. Their lifestyles in relation to feeding behaviour (feeding preferences, intake and turnover of phytodetrital carbon and nitrogen) and temperature adaptations were compared to obtain a closer definition of their specific roles in intertidal organic matter processing. For this comparison, we carried out a series of short-term laboratory incubations with stable isotope labelled (13C & 15N) detritus as food source. We compared the response of the two species to diatom detritus at three different temperatures (15 °C, 20 °C, 25 °C). The quite low metabolic nitrogen turnover in H. germanica was higher than the carbon turnover, and in contrast to the latter, not affected by temperature. This might be related with the chloroplast husbandry in this species and lower demands of food derived nitrogen sources. In contrast, A. tepida showed a very high, temperature-influenced intake and turnover rates with more excessive carbon turnover. Further, the latter species prefers a soft chlorophyte food source over diatom detritus, which is harder to break down. In conclusion, H. germanica is a highly specialized species with low rates of carbon and nitrogen budgeting. In contrast, A. tepida shows a generalist behaviour that links with high fluxes of organic matter (OM). Due to its high rates of OM processing and abundances, we conclude that A. tepida is an important key-player in intertidal carbon and nitrogen turnover, specifically in the short-term processing of OM and the mediation of dissolved nutrients to associated microbes and primary producers.

scholarly journals The distinct roles of two intertidal foraminiferal species in phytodetrital carbon and nitrogen fluxes – results from laboratory feeding experiments

2018 ◽  
Vol 15 (20) ◽  
pp. 6185-6198 ◽  
Author(s):  
Julia Wukovits ◽  
Max Oberrauch ◽  
Annekatrin J. Enge ◽  
Petra Heinz
Keyword(s):  
Organic Matter ◽  
Food Source ◽  
Nitrogen Sources ◽  
Carbon Turnover ◽  
Turnover Rates ◽  
Short Term ◽  
Carbon And Nitrogen ◽  
Nitrogen Turnover ◽  
Feeding Experiments ◽  
Different Temperatures

Abstract. Benthic foraminifera play a major role as primary consumers and detrivores redistributing organic carbon and nitrogen in intertidal environments. Here we compared the differences of phytodetrital carbon and nitrogen intake and turnover of two dominant intertidal foraminifera, Ammonia tepida and Haynesina germanica. Their lifestyles in relation to feeding behavior (feeding preferences, intake and turnover of phytodetrital carbon and nitrogen) and temperature adaptations were compared to obtain a closer definition of their specific roles in intertidal organic matter processing. For this comparison, we carried out a series of short-term laboratory incubations with stable-isotope-labeled (13C and 15N) detritus as the food source. We compared the response of the two species to diatom detritus at three different temperatures (15, 20, 25 ∘C). Ammonia tepida showed a very high, temperature-influenced intake and turnover rates with more excessive carbon turnover, compared to nitrogen. The fairly low metabolic nitrogen turnover in H. germanica was not affected by temperature and was higher than the carbon turnover. This might be related with the chloroplast husbandry in H. germanica and its lower demands for food-derived nitrogen sources. Ammonia tepida prefers a soft chlorophyte food source over diatom detritus, which is harder to break down. In conclusion, A. tepida shows a generalist behavior that links with high fluxes of organic matter (OM). Due to its high rates of OM processing and abundances, we conclude that A. tepida is an important key player in intertidal carbon and nitrogen turnover, specifically in the short-term processing of OM and the mediation of dissolved nutrients to associated microbes and primary producers. In contrast, H. germanica is a highly specialized species with low rates of carbon and nitrogen budgeting.

Colloidal systems in soils

1994 ◽  
Vol 52 ◽  
pp. 64-65
Author(s):  
J. Thieme ◽  
J. Niemeyer ◽  
P. Guttman
Keyword(s):  
Clay Minerals ◽  
Polymeric Materials ◽  
Spatial Arrangement ◽  
High Specific Surface Area ◽  
Turnover Rates ◽  
Colloidal Systems ◽  
Chemical Conditions ◽  
Aggregation Phenomena ◽  
Iron And Manganese ◽  
Soil Colloids

In soil science the fraction of colloids in soils is understood as particles with diameters smaller than 2μm. Clay minerals, aquoxides of iron and manganese, humic substances, and other polymeric materials are found in this fraction. The spatial arrangement (microstructure) is controlled by the substantial structure of the colloids, by the chemical composition of the soil solution, and by thesoil biota. This microstructure determines among other things the diffusive mass flow within the soils and as a result the availability of substances for chemical and microbiological reactions. The turnover of nutrients, the adsorption of toxicants and the weathering of soil clay minerals are examples of these surface mediated reactions. Due to their high specific surface area, the soil colloids are the most reactive species in this respect. Under the chemical conditions in soils, these minerals are associated in larger aggregates. The accessibility of reactive sites for these reactions on the surface of the colloids is reduced by this aggregation. To determine the turnover rates of chemicals within these aggregates it is highly desirable to visualize directly these aggregation phenomena.

Turnover and Distribution of 131Iodine-Labelled Human Fibrinogen

1964 ◽  
Vol 11 (02) ◽  
pp. 404-422 ◽  
Author(s):  
Annemarie Amris ◽  
C. J Amris
Keyword(s):  
Body Weight ◽  
Cancer Patient ◽  
Distribution Ratio ◽  
Half Life ◽  
Fibrinolytic Activity ◽  
The Other ◽  
Turnover Rates ◽  
Human Fibrinogen ◽  
Coagulation Defects ◽  
Fractional Turnover

Summary14 patients (5 diabetics with arteriosclerotic complications, 4 patients with thrombo-embolic disease, 4 with cirrhosis, coagulation defects and increased fibrinolytic activity, and 1 cancer patient) and 3 control patients were subjected to turnover studies with 13iodine labelled human fibrinogen.Half-life times in the control patients were found to be 4 days, the fractional turnover rates 19–23 per cent, of intravascular fibrinogen per day, and the absolute turnover 0.02 to 0.06 gm per day per kg. body weight. The other patient’s half-life times and turnover rates varied considerably from 0.9–5.5 days, 13–160 per cent, per day of intravascular fibrinogen and 0.02–0.4 gm per day per kg. body weight respectively.As fibrinogen unlike other proteins subjected to turnover studies, is converted to fibrin, it is not possible to measure the true intra-extravascular distribution ratio of fibrinogen. But intravascular fibrinogen could be approximated to constitute 68–99 per cent, of the total fibrinogen. There is justification in believing that fibrinogen is degradated through a continuous coagulation in equilibrium with fibrinolysis, and that the organism contains a greater mass of fibrin, the “fibrin pool”. Considerations of the turnover mechanism can however only be hypothetical.

Is Professional Commitment The Reason For Turnover Intentions of IT Professionals?

2019 ◽  
Vol 5 (1) ◽  
pp. 124
Author(s):  
Mohamed Buhari Mufitha ◽  
Su Teng Lee ◽  
Chen Chen Yong
Keyword(s):  
Job Satisfaction ◽  
Structural Equation ◽  
Turnover Intentions ◽  
Equation Model ◽  
Professional Commitment ◽  
Turnover Rates ◽  
It Professionals ◽  
Professional Advancement ◽  
Software Engineers ◽  
Job Satisfactions

Compared to others, professionals share distinguish workplace characteristics: one such is the high commitment to the professions over to working organizations. Information Technology (IT) professionals demonstrate higher turnover rates compared to others: their commitments to the profession has been suspected as a source of turnover. Considering their job satisfactions the present study aimed to investigate the influence of professional commitment on IT professionals’ turnover intentions. Data were collected from a sample of software engineers from Sri Lank using a survey questionnaire. The results of the structural equation model analysis concluded that professional commitment weakens IT professionals’ turnover intentions, which is partially mediated by job satisfaction. Professional commitment stimulates IT professionals’ job satisfaction. The findings challenge the presumption that IT professionals leave their organizations due to high commitments to the profession. Few factors were identified as significant in their job satisfactions: supervision, co-workers and work design. Pay and promotions were the least influencing job satisfaction factors. Managers may employ few strategies in their retention strategies: facilitate professional advancement needs within organizations, closely monitor supervision activities occurs and provide challenging and meaningful jobs. The study contributes to the turnover literature through empirical evidence on the influence of professional commitment on knowledge workers’ turnover intentions.

Revisiting Glycerol Esterification with Acetic Acid over Amberlyst-35 via Statistically Designed Experiments: Overcoming Transport Limitations

2019 ◽  
Author(s):  
Víctor Gabriel Baldovino Medrano ◽  
Karen V. Caballero ◽  
Hernando Guerrero-Amaya
Keyword(s):  
Acetic Acid ◽  
Active Sites ◽  
Batch Reactor ◽  
Catalyst Particle ◽  
Experimental Designs ◽  
Particle Sizes ◽  
Turnover Rates ◽  
Designed Experiments ◽  
Different Temperatures ◽  
Glycerol Esterification

Turnover rates for glycerol esterification with acetic acid over Amberlyst-35 were measured under different temperatures, reactants and active sites concentrations, and catalyst particle sizes. Data were collected in a batch reactor. Experiments were done following a sequence of factorial experimental designs.

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