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 Different Relationships of Fine Root Traits With Root Ammonium and Nitrate Uptake Rates in Conifer Forests

2021 ◽  
Author(s):  
Takumi Ito ◽  
Ayumi Tanaka-Oda ◽  
Taiga Masumoto ◽  
Maiko Akatsuki ◽  
Naoki Makita
Keyword(s):  
Morphological Traits ◽  
Nitrate Uptake ◽  
Fine Root ◽  
N Uptake ◽  
Root Traits ◽  
Inorganic N ◽  
Uptake Rates ◽  
Relationship Of ◽  
The Relationship

Abstract Purpose: Nitrogen (N) uptake by fine roots of trees is important for understanding the root physiological function in forest ecosystems, but a direct investigation of in situ rate of ammonium and nitrate uptake is limited. Thus, we aimed to clarify the inorganic N uptake rates among tree species and to determine the factors controlling N uptake through relationships with fine root traits in cool temperate forests.Methods: Using a solution depletion method for measuring N uptake, we observed the relationship of N uptake rate in the form of NH4+ and NO3– by an intact root system with root morphological traits, such as root diameter, specific root length (SRL), and root tissue density (RTD), and chemical traits, including root nitrogen (N) content. Results: The coniferous roots in this study preferred NH4+ form more than NO3– form. Across species, there were significant relationships between NH4+ uptake and diameter, SRL, and RTD, while these were significant only for RTD in NO3– form. Relationships between N uptake rates and root morphological traits differed between NH4+ and NO3–. Conclusions: We found that the relationship of inorganic N uptake with the morphological traits depends on the characteristics of the N form adsorbed through soil and tree N assimilation efficiency. An approach on the relationships of in situ N uptake with root traits will provide a breakthrough in our understanding of the root physiological function and the prediction of fundamental N acquisition strategies.

scholarly journals First in situ estimations of small phytoplankton carbon and nitrogen uptake rates in the Kara, Laptev, and East Siberian seas

2018 ◽  
Author(s):  
Bhavya P. Sadanandan ◽  
Jang Han Lee ◽  
Ho Won Lee ◽  
Jae Joong Kaang ◽  
Jae Hyung Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Nitrogen Uptake ◽  
N Uptake ◽  
Total Carbon ◽  
The Arctic ◽  
Carbon And Nitrogen ◽  
Uptake Rates ◽  
Wide Range ◽  
Small Phytoplankton

Abstract. Carbon and nitrogen uptake rates by small phytoplankton (0.7–5 μm) in the Kara, Laptev, and East Siberian seas in the Arctic Ocean were quantified using in situ isotope labelling experiments for the first time as part of the NABOS (Nansen and Amundsen Basins Observational System) program during August 21 to September 22, 2013. The depth integrated C, NO3−, and NH4+ uptake rates by small phytoplankton showed a wide range from 0.54 to 15.96 mg C m−2 h−1, 0.05 to 1.02 and 0.11 to 3.73 mg N m−2 h−1, respectively. The contributions of small phytoplankton towards the total C, NO3−, and NH4+ was varied from 24 to 89 %, 32 to 89 %, and 28 to 89 %, respectively. The turnover times for NO3− and NH4+ by small phytoplankton during the present study point towards the longer residence times (years) of the nutrients in the deeper waters, particularly for NO3−. Relatively, higher C and N uptake rates by small phytoplankton obtained during the present study at locations with less sea ice concentrations points towards the possibility of small phytoplankton thrive under sea ice retreat under warming conditions. The high contributions of small phytoplankton towards the total carbon and nitrogen uptake rates suggest capability of small size autotrophs to withstand in the adverse hydrographic conditions introduced by climate change.

Short term nitrogen dynamics in a small Brazilian wetland (Lago Infernão, São Paulo)

1989 ◽  
Vol 5 (3) ◽  
pp. 323-335 ◽  
Author(s):  
Clive Howard-Williams ◽  
F. de Esteves ◽  
J. E. Santos ◽  
M. T. Downes
Keyword(s):  
N Uptake ◽  
Algal Community ◽  
Nitrifying Bacteria ◽  
Temperature Changes ◽  
Time Period ◽  
Uptake Rates ◽  
Eichhornia Azurea ◽  
Short Time ◽  
Epiphyte Community

ABSTRACTWe have studied a number of related processes of the nitrogen cycle in a Brazilian floodplain lake to identify the major pools and pathways over a short time period. The study was centred on the littoral zone dominated by the floating plantEichhornia azurea, which has a large epiphyte algal community of which heterocystous cyanobacteria were the major components. The water column was continuously undersaturated with oxygen although some elevated values (to 60% saturation) were recorded in the macrophyte beds in the afternoon. Marked diel temperature changes were documented. NH4-N dominated the dissolved N component in the water with maximal values (60 mg m−3) at lowest O2, concentrations early in the morning. Nitrogen fixation (acetylene reduction) of the epiphyte community showed marked diel changes with daily values of 5 mg N fixed m−2day−1(based on 3:1 C2H4:N2ratio). Macrophyte NH4-N uptake rates (in situincubations) were 93 mg N m−2day−1. The activities of nitrifying bacteria could not be detected with the nitrapyrin block on dark CO2fixation but denitrification (acetylene block technique) was recorded in the sediments when enhanced with NO-3. The major pathways of aquatic nitrogen involved macrophyte uptake and sediment release of NH4-N.

Evaluation of Maize Inbreds for Vegetative Nitrate Uptake and Assimilation

1989 ◽  
Vol 16 (2) ◽  
pp. 161 ◽  
Author(s):  
RT Weiland
Keyword(s):  
Nitrate Uptake ◽  
N Uptake ◽  
Dry Weight ◽  
Root Surface ◽  
Root Surface Area ◽  
Controlled Environment ◽  
Uptake Rates ◽  
Total Plant ◽  
Maize Inbreds ◽  
Hydroponic Conditions

Twelve maize (Zea mays L.) inbred lines were cultured under hydroponic conditions in a controlled environment room for evaluation of NO3--N uptake, subsequent translocation patterns and utilisation. Prior to harvest (8-10-leaf stage), inbred roots were exposed to 24 h of 10 atom % 15NO3--N. Differences for N contents and biomass were determined. Root dry weight (RDW) was significantly correlated (r = 0.93) with root surface area. Significant inbred differences were found when N content in the plant was based on RDW. When based on 15N during the 24 h, the amount of N absorbed varied between 30 and 71 mg per plant for the inbreds. Uptake rates ranged between 8.7 and 14.4 mg g-1 day-1 RDW. Nitrogen uptake over the 24 h based on RDW and total plant-N contents based on RDW were significantly (P< 0.001) correlated, implying that uptake rates were constant up to mid-vegetative stages for these genotypes. Of the 15N absorbed, between 30 and 61% was reduced by the inbreds and the amount reduced varied with plant tissue. The total amount reduced ranged between 0.72 and 1.25 mg g-1 dry weight.

Stimulation of Nitrate Uptake and Photosynthesis by Molybdenum in Castle Lake, California

1980 ◽  
Vol 37 (4) ◽  
pp. 707-712 ◽  
Author(s):  
R. P. Axler ◽  
R. M. Gersberg ◽  
C. R. Goldman
Keyword(s):  
Nitrate Uptake ◽  
Phytoplankton Community ◽  
Euphotic Zone ◽  
Growing Season ◽  
Uptake Rates ◽  
Early Portion ◽  
Rate Of Photosynthesis ◽  
Castle Lake ◽  
Stimulation Of

The uptake rates of 15NO3 and 14CO2 by the natural phytoplankton community at Castle Lake, California, were measured in situ as responses to 5 μg∙L−1 additions of molybdenum. Stimulation of both nitrate uptake and photosynthesis occurred in water samples containing only relatively high amounts of nitrate. This response to added molybdenum disappeared as the growing season progressed and nitrate was depleted in the euphotic zone. Although molybdenum stimulated nitrate uptake by 55% in water collected from the lower euphotic zone, it did not increase the rate of CO2 uptake because at that depth the rate of photosynthesis was most limited by light intensity and not by nitrogen. An analysis of molybdenum bioassays from 1959 to 1963 is integrated with these findings and points to the importance of molybdenum for phytoplankton growth during the early portion of the growing season when nitrate concentrations in the euphotic zone are maximal.Key words: molybdenum, nitrate, nitrate uptake, micronutrient bioassays

scholarly journals First in situ estimations of small phytoplankton carbon and nitrogen uptake rates in the Kara, Laptev, and East Siberian seas

2018 ◽  
Vol 15 (18) ◽  
pp. 5503-5517 ◽  
Author(s):  
P. Sadanandan Bhavya ◽  
Jang Han Lee ◽  
Ho Won Lee ◽  
Jae Joong Kang ◽  
Jae Hyung Lee ◽  
...  
Keyword(s):  
Sea Ice ◽  
Nitrogen Uptake ◽  
Isotope Labeling ◽  
N Uptake ◽  
The Arctic ◽  
Carbon And Nitrogen ◽  
Uptake Rates ◽  
Small Phytoplankton ◽  
C And N

Abstract. Carbon and nitrogen uptake rates by small phytoplankton (0.7–5 µm) in the Kara, Laptev, and East Siberian seas in the Arctic Ocean were quantified using in situ isotope labeling experiments; this research, which was novel and part of the NABOS (Nansen and Amundsen Basins Observational System) program, took place from 21 August to 22 September 2013. The depth-integrated carbon (C), nitrate (NO3-), and ammonium (NH4+) uptake rates by small phytoplankton ranged from 0.54 to 15.96 mg C m−2 h−1, 0.05 to 1.02 mg C m−2 h−1, and 0.11 to 3.73 mg N m−2 h−1, respectively. The contributions of small phytoplankton towards the total C, NO3-, and NH4+ varied from 25 % to 89 %, 31 % to 89 %, and 28 % to 91 %, respectively. The turnover times for NO3- and NH4+ by small phytoplankton found in the present study indicate the longer residence times (years) of the nutrients in the deeper waters, particularly for NO3-. Additionally, the relatively higher C and N uptake rates by small phytoplankton obtained in the present study from locations with less sea ice concentration indicate the possibility that small phytoplankton thrive under the retreat of sea ice as a result of warming conditions. The high contributions of small phytoplankton to the total C and N uptake rates suggest the capability of small autotrophs to withstand the adverse hydrographic conditions introduced by climate change.

scholarly journals Some observations on marine phytoplankton kinetics: 2. The effect of nitrate and ammonium concentrations on the growth and uptake rates of the natural population of Ubatuba region, SP (23ºS, 045ºW)

1983 ◽  
Vol 32 (1) ◽  
pp. 83-90
Author(s):  
Gilda Schmidt
Keyword(s):  
Growth Rate ◽  
Natural Population ◽  
Uptake Rate ◽  
Culture Media ◽  
Cell Number ◽  
Marine Phytoplankton ◽  
Uptake Rates ◽  
Nitrate Concentrations

The phytoplankton Ks anã Vmax as a function of ammonium and nitrate concentrations were determined. The growth rate was estimated from measurements on synthesized chlorophyll-α and the cell number in the. culture media. The uptake rate was determined as to the consumption of ammonium and nitrate after the nutrients depletion from culture media.

scholarly journals Production regime and associated N cycling in the vicinity of Kerguelen Island, Southern Ocean

2015 ◽  
Vol 12 (21) ◽  
pp. 6515-6528 ◽  
Author(s):  
A. J. Cavagna ◽  
F. Fripiat ◽  
M. Elskens ◽  
P. Mangion ◽  
L. Chirurgien ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Primary Production ◽  
Mixed Layer ◽  
Nitrate Uptake ◽  
Net Primary Production ◽  
N Uptake ◽  
Euphotic Zone ◽  
Global Ocean ◽  
Kerguelen Plateau ◽  
New Production

Abstract. Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO3− and NH4+), and nitrification rates were measured at eight stations in austral spring 2011 (October–November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1 respectively) compared to the HNLC reference site (12 mmol C m−2 d−1 and 0.06 d−1 respectively). Primary production was mainly sustained by nitrate uptake, with f ratios (corresponding to NO3−-uptake / (NO3−-uptake + NH4+-uptake)) lying at the upper end of the observations for the Southern Ocean (up to 0.9). We report high rates of nitrification (up to ~ 3 μmol N L−1 d−1, with ~ 90 % of them < 1 μmol N L−1 d−1) typically occurring below the euphotic zone, as classically observed in the global ocean. The specificity of the studied area is that at most of the stations, the euphotic layer was shallower than the mixed layer, implying that nitrifiers can efficiently compete with phytoplankton for the ammonium produced by remineralization at low-light intensities. Nitrate produced by nitrification in the mixed layer below the euphotic zone is easily supplied to the euphotic zone waters above, and nitrification sustained 70 ± 30 % of the nitrate uptake in the productive area above the Kerguelen Plateau. This complicates estimations of new production as potentially exportable production. We conclude that high productivity in deep mixing system stimulates the N cycle by increasing both assimilation and regeneration.

Ammonia and Nitrate Uptake in the Lower Great Lakes

1980 ◽  
Vol 37 (9) ◽  
pp. 1365-1372 ◽  
Author(s):  
T. P. Murphy
Keyword(s):  
Great Lakes ◽  
Nitrate Uptake ◽  
Nutrient Concentrations ◽  
Short Term ◽  
Low Concentrations ◽  
Uptake Rates ◽  
Low K ◽  
Slow Turnover

Uptake of NH4+ is consistent with Michaelis–Menten kinetics in the Lower Great Lakes only if one assumes that the indophenol method of measuring NH4+ overestimates the in situ concentration. Short-term incubations were found necessary to avoid induction of nitrate uptake or changes in the rates of NH4+ uptake that occurred in long-term incubations. Uptake rates of nitrate are slow most of the summer. Since the nitrate is also present in low concentrations, most of the summer regeneration of nitrate must be very slow. The slow turnover of particulate N, low nutrient concentrations, slow rate of uptake relative to their ability to take up nitrogen, and the high affinity for ammonia (low Kt) suggest that in summer the primary productivity of the Lower Great Lakes is restricted by nitrogen deficiency.Key words: ammonia, nitrate, Lower Great Lakes

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