Uptake of ammonium by four species of macroalgae in Port Phillip Bay, Victoria, Australia

1999 ◽  
Vol 50 (6) ◽  
pp. 515 ◽  
Author(s):  
Stuart J. Campbell
Keyword(s):  
Competitive Advantage ◽  
Nutrient Uptake ◽  
Uptake Rate ◽  
Undaria Pinnatifida ◽  
Ammonium Uptake ◽  
N Availability ◽  
Low Concentrations ◽  
Uptake Rates ◽  
Maximum Uptake Rate ◽  
Saturation Rate

The uptake rates of ammonium were determined for three species of native macroalgae and an exotic macroalga from Port Phillip Bay. All species exhibited rate-saturated mechanisms of uptake described by Michaelis–Menten uptake kinetics. At the highest concentration examined (28.6 µmol NH4-N) Hincksia sordida had a higher rate of uptake (435 µmol NH4 -N g dry wt–1 h–1) than Ulva sp. (108 µmol NH4-N g dry wt–1 h–1) or Polysiphonia decipiens (53 µmol NH4 -N g dry wt–1 h–1). Maximum surge uptake rate was highest for H. sordida and lowest for P. decipiens (802 and 57 µmol NH4 -N g dry wt–1 h–1 respectively). The introduced phaeophyte Undaria pinnatifida had an intermediate capacity for ammonium uptake which was dependent on blade maturity. Differences in the ratio of maximum uptake rate to half-saturation rate between surge and assimilation uptake phases suggest a propensity for some species to take up ammonium at low concentrations. The relationships between nutrient uptake and growth among species would afford mature U. pinnatifida, H. sordida and Ulva sp. a competitive advantage for ammonium uptake in winter during high N availability, whereas P. decipiens would be able to exploit low N concentrations in spring and summer.

Use of a Self-Cleaning, In-line Filter to Continuously Monitor Phytoplankton Nutrient Uptake Rates

1984 ◽  
Vol 41 (3) ◽  
pp. 540-544 ◽  
Author(s):  
J. S. Parslow ◽  
P. J. Harrison ◽  
P. A. Thompson
Keyword(s):  
Nutrient Uptake ◽  
Uptake Rate ◽  
Skeletonema Costatum ◽  
Thalassiosira Pseudonana ◽  
Ammonium Concentration ◽  
Marine Diatoms ◽  
Response Characteristics ◽  
Uptake Rates ◽  
Laboratory Cultures ◽  
Self Cleaning

Our new technique allows the decline in ambient ammonium concentration to be followed continuously during phytoplankton uptake experiments. A self-cleaning, in-line filter permits the continuous separation of cells from the medium for nutrient determination by an autoanalyzer. The technique works well with laboratory cultures of the marine diatoms Thalassiosira pseudonana and Skeletonema costatum. Changes in uptake rate on time scales of 1 min or longer can be resolved, the resolution being limited by the response characteristics of the autoanalyzer.

scholarly journals Investigating equations for measuring dissolved inorganic nutrient uptake in oligotrophic conditions

2020 ◽  
Author(s):  
Michael R. Stukel
Keyword(s):  
Nutrient Uptake ◽  
Ecosystem Model ◽  
Ammonium Uptake ◽  
Nutrient Concentrations ◽  
Nutrient Regeneration ◽  
Isotope Tracer ◽  
Uptake Rates ◽  
Label Incorporation ◽  
Moderate Complexity

ABSTRACTMultiple different equations have been used to quantify nutrient uptake rates from stable isotope tracer label incorporation experiments. Each of these equations implicitly assumes an underlying model for phytoplankton nutrient uptake behavior within the incubation bottle and/or pelagic environment. However, the applicability of different equations remains in question and uncertainty arising from subjective choices of which equation to use is never reported. In this study, I use two approaches to investigate the conditions under which different nutrient uptake equations should be used. First, I utilized a moderate-complexity pelagic ecosystem model that explicitly models the δ15N values of all model compartments (NEMURO+15N) to conduct simulated nitrate uptake and ammonium uptake incubations and quantify the accuracy of different nutrient uptake equations. Second, I used results of deckboard diel nutrient uptake experiments to quantify the biases of 24-h incubations relative to six consecutive 4-h incubations. Using both approaches, I found that equations that account for nutrient regeneration (i.e., isotope dilution) are more accurate than equations that do not, particularly when nutrient concentrations are low but uptake is relatively high. Furthermore, I find that if the goal is to estimate in situ uptake rates it is appropriate to use an in situ correction to standard equations. I also present complete equations for quantifying uncertainty in nutrient uptake experiments using each nutrient uptake equation and make all of these calculations available as Excel spreadsheets and Matlab scripts.

scholarly journals A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean

2014 ◽  
Vol 11 (4) ◽  
pp. 1829-1869
Author(s):  
R. Philibert ◽  
H. Waldron ◽  
D. Clark
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Nitrogen Uptake ◽  
Uptake Rate ◽  
Nitrate Uptake ◽  
Day Length ◽  
Ammonium Uptake ◽  
Ammonium Concentration ◽  
Uptake Rates ◽  
The Impact

Abstract. Primary production in the Southern Ocean has been shown to be regulated by light and nutrients (such as silicate and iron) availability. However, the impact of these factors vary seasonally and differ from region to region. The seasonal cycle of primary production in this region is not fully resolved over an annual scale due to the lack of winter in situ measurements. In this study, nitrate and ammonium uptake rates were measured using 15N tracers during a winter cruise in July 2012 and a summer cruise in February/March 2013. In winter, nitrogen uptake rates were measured at 55% and 1% of the surface photosynthetically active radiation (sPAR). The summer uptake rates were measured at 4 light depths corresponding to 55, 30, 10 and 3% sPAR. The integrated nitrate uptake rates during the winter cruise ranged from 0.16–5.20 (average 1.14) mmol N m−2 d−1 while the ammonium uptake rates ranged from 0.6–32.8 (average 6.72) mmol N m−2 d−1. During the summer cruise, the mean integrated nitrate uptake rate was 0.34 mmol N m−2 d−1 with a range between 0.16–0.65 mmol N m−2 d−1. The integrated ammonium uptake rate averaged 5.61 mmol N m−2 d−1 and ranged from 1.44–11.28 mmol N m−2 d−1. The factors controlling primary production in winter and summer were investigated. During the winter cruise, it was found the different nitrogen uptake regimes were not separated by fronts. Light (in terms of day length) and ammonium concentration had the most influence on the nitrogen uptake regime. In the summer, increases in the mixed layer depth (MLD) resulted in increased nitrogen uptake rates. This suggests that the increases in the MLD could be alleviating nutrient limitations experienced by the phytoplankton at the end of summer.

scholarly journals A geographical and seasonal comparison of nitrogen uptake by phytoplankton in the Southern Ocean

Ocean Science ◽  
2015 ◽  
Vol 11 (2) ◽  
pp. 251-267 ◽  
Author(s):  
R. Philibert ◽  
H. Waldron ◽  
D. Clark
Keyword(s):  
Southern Ocean ◽  
Nitrogen Uptake ◽  
Uptake Rate ◽  
Nitrate Uptake ◽  
Day Length ◽  
Ammonium Uptake ◽  
Ammonium Concentration ◽  
Atlantic Sector ◽  
Uptake Rates ◽  
The Impact

Abstract. The impact of light and nutrients (such as silicate and iron) availability on nitrogen uptake and primary production vary seasonally and regionally in the Southern Ocean. The seasonal cycle of nitrogen uptake by phytoplankton in the Southern Ocean is not fully resolved over an annual scale due to the lack of winter in situ measurements. In this study, nitrate and ammonium uptake rates were measured using 15N tracers during a winter cruise in July 2012 and a summer cruise in February–March 2013. The winter cruise consisted of two legs: leg 1 extended from Cape Town to the ice margin along the GoodHope line and leg 2 stretched from the ice margin to Marion Island. The summer cruise was mostly focused on the subantarctic zone of the Atlantic sector. In winter, nitrogen uptake rates were measured at 55 and 1% of the surface photosynthetically active radiation (sPAR). The summer uptake rates were measured at four light depths corresponding to 55, 30, 10 and 3% sPAR. The integrated nitrate uptake rates during the winter cruise ranged from 0.17 to 5.20 mmol N m−2 d−1 (average 1.14 mmol N m−2 d−1) while the ammonium uptake rates ranged from 0.60 to 32.86 mmol N m−2 d−1 (average 6.73 mmol N m−2 d−1). During the summer cruise, the mean-integrated nitrate uptake rate was 0.20 mmol N m−2 d−1 with a range between 0.10 and 0.38 mmol N m−2 d−1. The integrated ammonium uptake rate averaged 4.39 mmol N m−2 d−1 and ranged from 1.12 to 9.05 mmol N m−2 d−1. The factors controlling nitrogen uptake in winter and summer were investigated. During the winter cruise, it was found that the different nitrogen uptake regimes were not separated by the fronts of the Antarctic Circumpolar Current (ACC). Light (in terms of day length) and ammonium concentration had the most influence on the nitrogen uptake. In the summer, increases in the mixed layer depth (MLD) resulted in increased nitrogen uptake rates. This suggests that the increases in the MLD could be alleviating nutrient limitations experienced by the phytoplankton at the end of summer.

Phosphate Uptake Rates of Phytoplankton Assemblages Grown at Different Dilution Rates in Semicontinuous Culture

1986 ◽  
Vol 43 (8) ◽  
pp. 1474-1481 ◽  
Author(s):  
C. A. Suttle ◽  
P. J. Harrison
Keyword(s):  
Dilution Rate ◽  
Uptake Rate ◽  
Time Course ◽  
Phytoplankton Community ◽  
Phytoplankton Assemblages ◽  
Uptake Rates ◽  
Maximum Uptake Rate ◽  
Synechococcus Sp ◽  
The Relationship ◽  
Natural Phytoplankton

We studied the effects of pulsed nutrient supplies on the physiology of natural phytoplankton assemblages. A natural phytoplankton community, from an oligotrophic lake, was grown at several dilution rates from 0.1 to 1.5∙d−1 in P-limited semicontinuous cultures. Particulate C:P and N:P ratios (by atoms) were approximately 300:1 and 50:1, respectively, at the lowest dilution rate and 40:1 and 7:1, respectively, at the highest dilution rate. This demonstrates that a range of P-limited conditions can be established using the semicontinuous culturing technique. The time-course of uptake, in response to a saturating addition of phosphate, revealed that there was a short lag before maximum rates of uptake were observed at all but the highest dilution rate, and that maximum uptake rates over the first 30 min of incubation were higher at intermediate dilution rates. Subsequent to the maximum uptake rate occurring, the relationship between uptake rate and time was species dependent. In Oscillatoria sp. dominated cultures the uptake rates declined with increasing cellular P, and the rates of these declines increased with dilution rate; in Synechococcus sp. dominated cultures the uptake rates remained constant and were independent of cellular P.

Potassium depletion improves myocardial potassium uptake in vivo

2004 ◽  
Vol 287 (1) ◽  
pp. C135-C141 ◽  
Author(s):  
Henning Bundgaard
Keyword(s):  
Uptake Rate ◽  
High Plasma ◽  
Potassium Depletion ◽  
Uptake Capacity ◽  
K Uptake ◽  
Impulse Generation ◽  
Uptake Rates ◽  
Clinical Interest ◽  
A Minor

Potassium depletion (KD) is a very common clinical entity often associated with adverse cardiac effects. KD is generally considered to reduce muscular Na-K-ATPase density and secondarily reduce K uptake capacity. In KD rats we evaluated myocardial Na-K-ATPase density, ion content, and myocardial K reuptake. KD for 2 wk reduced plasma K to 1.8 ± 0.1 vs. 3.5 ± 0.2 mM in controls ( P < 0.01, n = 7), myocardial K to 80 ± 1 vs. 86 ± 1 μmol/g wet wt ( P < 0.05, n = 7), increased Mg, and induced a tendency to increased Na. Myocardial Na-K-ATPase α2-subunit abundance was reduced by ∼30%, whereas increases in α1- and K-dependent pNPPase activity of 24% ( n = 6) and 13% ( n = 6), respectively, were seen. This indicates an overall upregulation of the myocardial Na-K pump pool. KD rats tolerated a higher intravenous KCl dose. KCl infusion until animals died increased myocardial K by 34% in KD rats and 18% in controls ( P < 0.05, n = 6 for both) but did not induce different net K uptake rates between groups. However, clamping plasma K at ∼5.5 mM by KCl infusion caused a higher net K uptake rate in KD rats (0.22 ± 0.04 vs. 0.10 ± 0.03 μmol·g wet wt−1·min−1; P < 0.05, n = 8). In conclusion, a minor KD-induced decrease in myocardial K increased Na-K pump density and in vivo increased K tolerance and net myocardial K uptake rate during K repletion. Thus the heart is protected from major K losses and accumulates considerable amounts of K during exposure to high plasma K. This is of clinical interest, because a therapeutically induced rise in myocardial K may affect contractility and impulse generation-propagation and may attenuate increased myocardial Na, the hallmark of heart failure.

scholarly journals Defoliation Tolerance and Ammonium Uptake Rate in Perennial Tussock Grasses

2004 ◽  
Vol 57 (1) ◽  
pp. 82 ◽  
Author(s):  
Carolina Saint Pierre ◽  
Carlos Alberto Busso ◽  
Oscar Montenegro ◽  
Gustavo D. Rodriguez ◽  
Hugo D. Giorgetti ◽  
...  
Keyword(s):  
Uptake Rate ◽  
Ammonium Uptake ◽  
Tussock Grasses

scholarly journals Effect of incubation time and substrate concentration on N-uptake rates by phytoplankton in the Bay of Bengal

2005 ◽  
Vol 2 (5) ◽  
pp. 1331-1352
Author(s):  
S. Kumar ◽  
R. Ramesh ◽  
S. Sardesai ◽  
M. S. Sheshshayee
Keyword(s):  
Incubation Time ◽  
Uptake Rate ◽  
Nitrate Uptake ◽  
N Uptake ◽  
Marine Phytoplankton ◽  
Total Production ◽  
New Production ◽  
Urea Uptake ◽  
Uptake Rates

Abstract. We report here the results of three experiments, which are slight variations of the 15N method (JGOFS protocol) for determination of new production. The first two test the effect of (i) duration of incubation time and (ii) concentration of tracer added on the uptake rates of various N-species (nitrate, ammonium and urea) by marine phytoplankton; while the third compares in situ and deck incubations from dawn to dusk. Results indicate that nitrate uptake can be underestimated by experiments where incubation times shorter than 4h or when more than 10% of the ambient concentration of nitrate is added prior to incubation. The f-ratio increases from 0.28 to 0.42 when the incubation time increases from two to four hours. This may be due to the observed increase in the uptake rate of nitrate and decrease in the urea uptake rate. Unlike ammonium [y{=}2.07x{-}0.002\\, (r2=0.55)] and urea uptakes [y{=}1.88x{+}0.004 (r2=0.88)], the nitrate uptake decreases as the concentration of the substrate (x) increases, showing a negative correlation [y{=}-0.76x+0.05 (r2=0.86)], possibly due to production of glutamine, which might suppress nitrate uptake. This leads to decline in the f-ratio from 0.47 to 0.10, when concentration of tracer varies from 0.01 to 0.04μ M. The column integrated total productions are 519 mg C m-2 d-1 and 251 mg C m-2 d-1 for in situ and deck incubations, respectively. The 14C based production at the same location is ~200 mg C m-2 d-1, which is in closer agreement to the 15N based total production measured by deck incubation.

scholarly journals Uptake of referrals for women with positive perinatal depression screening results and the effectiveness of interventions to increase uptake: a systematic review and meta-analysis

2020 ◽  
Vol 29 ◽  
Author(s):  
WQ Xue ◽  
KK Cheng ◽  
D Xu ◽  
X Jin ◽  
WJ Gong
Keyword(s):  
Uptake Rate ◽  
Observational Studies ◽  
Perinatal Depression ◽  
Meta Analysis ◽  
Depression Screening ◽  
Site Assessment ◽  
Uptake Rates ◽  
Subgroup Analyses ◽  
Quasi Experimental ◽  
Meta Regression

Abstract Aims Perinatal depression threatens the health of maternal women and their offspring. Although screening programs for perinatal depression exist, non-uptake of referral to further mental health care after screening reduces the utility of these programs. Uptake rates among women with positive screening varied widely across studies and little is known about how to improve the uptake rate. This study aimed to systematically review the available evidence on uptake rates, estimate the pooled rate, identify interventions to improve uptake of referral and explore the effectiveness of those interventions. Methods This systematic review has been registered in PROSPERO (registration number: CRD42019138095). We searched Pubmed, Web of Science, Cochrane Library, Ovid, Embase, CNKI, Wanfang Database and VIP Databases from database inception to January 13, 2019 and scanned reference lists of relevant researches for studies published in English or Chinese. Studies providing information on uptake rate and/or effectiveness of interventions on uptake of referral were eligible for inclusion. Studies were excluded if they did not report the details of the referral process or did not provide exact uptake rate. Data provided by observational studies and quasi-experimental studies were used to estimate the pooled uptake rate through meta-analysis. We also performed meta-regression and subgroup analyses to explore the potential source of heterogeneity. To evaluate the effectiveness of interventions, we conducted descriptive analyses instead of meta-analyses since there was only one randomised controlled trial (RCT). Results Of 2302 records identified, 41 studies were eligible for inclusion, including 39 observational studies (n = 9337), one quasi-experimental study (n = 43) and one RCT (n = 555). All but two studies were conducted in high-income countries. The uptake rates reported by included studies varied widely and the pooled uptake rate of referral was 43% (95% confidence intervals [CI] 35–50%) by a random-effect model. Meta-regression and subgroup analyses both showed that referral to on-site assessment or treatment (60%, 95% CI 51–69%) had a significantly higher uptake rate than referral to mental health service (32%, 95% CI 23–41%) (odds ratio 1.31, 95% CI 1.13–1.52). The included RCT showed that the referral intervention significantly improved the uptake rate (p ＜ 0.01). Conclusions Almost three-fifths of women with positive screening results do not take up the referral offers after perinatal depression screening. Referral to on-site assessment and treatment may improve uptake of referral, but the quality of evidence on interventions to increase uptake was weak. More robust studies are needed, especially in low-and middle-income countries.

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