Phytoplankton uptake of ammonium and urea during growth on oxidized forms of nitrogen

Horrigan, SG; McCarthy, James J.

doi:10.1093/plankt/4.2.379

Cited by 47 publications

(27 citation statements)

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“…Thus, urea decomposition activities in June and September were not suppressed by the very high ammonium concentrations. Our results are intriguing in view of the fact that pM levels of ammonium are known to inhibit urea decomposition (Horrigan & McCarthy 1982, Mitamura 198613, Tamminen & Irmisch 1996. The substantial activity of urea decomposition was reflected by relatively rapid turnover times of urea (on average 9.2 d) during June and September.…”

Section: Die1 Variations Of Urea Decompositionmentioning

confidence: 78%

“…In contrast, ammonium concentrations in our study area measured up to 100-fold greater. Urea decomposition activity had previously been reported to be inhibited by ammonium concentration greater than 1 pM in both seawater and batch cultures of marine diatoms (Horrigan & McCarthy 1982, Tamrninen & Irrnisch 1996. Based on the works of Mitamura (1986b) and Mitamura & Saijo (1986) in Lake Biwa, urea decomposition in freshwaters seemed to be inhibited by ammonium concentrations greater than 1 PM.…”

Section: Die1 Variations Of Urea Decompositionmentioning

confidence: 95%

“…The decomposition of urea by phytoplankton is known to be controlled by light (Webb & Hass 1976), ammonium concentration (Horrigan & McCarthy 1982, Park et al 1993, Tamminen & Irmisch, 1996 and water temperature (Mitamura 1986b). Webb & Hass (1976) reported the diel periodicity of urea decomposition in the York River and observed a zero 'Addressee for correspondence.…”

Section: Introductionmentioning

confidence: 99%

“…E-mail: bccho@plaza.snu,ac,kr rate of urea decomposition during the nighttime. The presence of ammonium has often been reported to inhibit urea decomposition in phytoplankton in both seawater and batch cultures of marine diatoms (Horrigan & McCarthy 1982, Tamminen & Irrnisch 1996. Using ISN-labelled urea, Mitamura (198613) found that urea uptake was suppressed 15 to 30 % by ammonium concentration greater than 1 PM in Lake Biwa.…”

Section: Introductionmentioning

confidence: 99%

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Urea decomposition activities in an ammonium enriched freshwater pond

Park¹,

Shim²,

Cho³

1997

Aquat. Microb. Ecol.

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Urea decomposition activities, urea and ammonium concentrations, and the concentration of chlorophyll a (chl a ) were measured in an ammonium enriched, hypertrophic freshwater pond at 5 to 7 h intervals during 3 &el cycles on June 27 to 28, September 6 to 7,1992 and February 14 to 15,1993. The study site was characterized by very high anlmonium concentrations, ranging from 123.6 to 403.6 p M . During the study period, the urea concentration ranged from 1 3 to 9.1 pM and chl a concentration ranged from 81.5 to 211.8 pg 1-'. In 2 of 3 diel cycles the nighttime urea decomposition rate in whole waters was higher than the daytime decomposition rate; in 1 diel experiment the nighttime decomposition rate was 56.4 % of the daytime rate, indicating that the variation of urea decomposition rate was not associated with natural light/dark cycles. Despite the very high ammonium concentrations, substantial urea decomposition rates (5.5 to 80.8 nM h-') were observed, particularly in June and September. Such high decomposition rates were due to high chl a-specific activity rather than due to large phytoplankton biomass and low activity. When urea concentration was high (ca >2 PM), the urea decomposition rate showed a linear increase with increasing urea concentration even in the presence of high ammonium concentrations (range of 123.6 to 403.6 PM), suggesting that elevated urea concentration mitigates the repressive effect of ammonium on urea decomposition. The urea decon~position rate in GF/C filtrates (mainly bacterial-size fractions) ranged from negligible to 39.3 nM h-', representing an average of 47.1 % of the activity in whole pond waters. This study suggests that urea decomposition activity in an ammonium enriched freshwater pond is significantly elevated and controlled by the urea concentration, and that bactena might contribute substantially to urea decomposition rate in a hypertrophic freshwater pond.

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Section: Die1 Variations Of Urea Decompositionmentioning

confidence: 78%

Section: Die1 Variations Of Urea Decompositionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Urea decomposition activities in an ammonium enriched freshwater pond

Park¹,

Shim²,

Cho³

1997

Aquat. Microb. Ecol.

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“…It is suggested that a similar regulatory system to that in Escherichla coli (Magasanik 1988), in which GLN/2-oxoglutarate regulates GS activity, may operate in microalgae (see text) NH; by NOT-grown cells (e.g. Horrigan & McCarthy 1982). However, such stress is not often growth limiting and C/N ratios of NH: and NO,?…”

Section: N-stress and Gene Regulationmentioning

confidence: 99%

The determination of nitrogen status in microalgae

Flynn¹

1990

Mar. Ecol. Prog. Ser.

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Present methods used for the determination of N-status in microalgae typically involve testing for the existence of gross metabolic changes which develop in response to N-stress. Such approaches have 2 problems. First, the experimental tech~uques may be inappropriate for the species present and may perturb the organisms, possibly creating artifacts. Second, these gross changes, such as changes in rates of CO2-fixation and N-source uptake, may be affected by factors other than N-stress. There is a need to develop methods to detect metabolic changes which themselves trigger the genetic response to N-stress rather than to detect the products of that response. Such changes are likely to be in relative proportions of key metabolites of C and N metabolism, as In bacteria. It is suggested that only in the presence of excess NH: are the processes of cellular response to N-stress fully suppressed. As a consequence, microalgae throughout the oceans may show some symptoms of N-stress. The level of derepression of the N-stress responses which corresponds to growth-limitation, and hence is of ecological significance, needs to b e determined.

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Pluses and minuses of ammonium and nitrate uptake and assimilation by phytoplankton and implications for productivity and community composition, with emphasis on nitrogen-enriched conditions

et al. 2015

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Anthropogenic activities are altering total nutrient loads to many estuaries and freshwaters, resulting in high loads not only of total nitrogen (N), but in some cases, of chemically reduced forms, notably NH 4 that promote vs. repress NO -3 uptake, assimilation, and growth in different phytoplankton groups and under different growth conditions are not well understood. Here, we review N metabolism first in a "generic" eukaryotic cell, and the contrasting metabolic pathways and regulation of NH 1 4 and NO 2 3 when these substrates are provided individually under equivalent growth conditions. Then the metabolic interactions of these substrates are described when both are provided together, emphasizing the cellular challenge of balancing nutrient acquisition with photosynthetic energy balance in dynamic environments. Conditions under which dissipatory pathways such as dissimilatory NO 2 3 / NO 2 2 reduction to NH 1 4 and photorespiration that may lead to growth suppression are highlighted. While more is known about diatoms, taxon-specific differences in NH 1 4 and NO 2 3 metabolism that may contribute to changes in phytoplankton community composition when the composition of the N pool changes are presented. These relationships have important implications for harmful algal blooms, development of nutrient criteria for management, and modeling of nutrient uptake by phytoplankton, particularly in conditions where eutrophication is increasing and the redox state of N loads is changing.

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Phytoplankton uptake of ammonium and urea during growth on oxidized forms of nitrogen

Cited by 47 publications

References 0 publications

Urea decomposition activities in an ammonium enriched freshwater pond

Urea decomposition activities in an ammonium enriched freshwater pond

The determination of nitrogen status in microalgae

Pluses and minuses of ammonium and nitrate uptake and assimilation by phytoplankton and implications for productivity and community composition, with emphasis on nitrogen-enriched conditions

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