DIEL RHYTHM OF ALGAL PHOSPHATE UPTAKE RATES IN P‐LIMITED CYCLOSTATS AND SIMULATION OF ITS EFFECT ON GROWTH AND COMPETITION<sup>1</sup>

Ahn, Chi‐Yong; Chung, An‐Sik; Oh, Hee‐Mock

doi:10.1046/j.1529-8817.2002.01232.x

Cited by 26 publications

(20 citation statements)

References 42 publications

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“…No previous studies on natural samples identified the organisms with higher PO 4 3− uptake in the light. Most previous studies on the effect of light on PO 4 3− uptake either used phytoplankton cultures (Jansson 1993, Donald et al 1997, Riegman et al 2000, Ahn et al 2002, Kumar et al 2009 or analyzed whole or size-fractionated water samples (Perry 1976, Reshkin & Knauer 1979, Nalewajko & Garside 1983, Nalewajko & Lee 1983, Björkman et al 2000. In contrast to past studies, we sorted samples into 2 targeted microbial groups (Prochlorococcus and non-pigmented picoplankton).…”

Section: Discussionmentioning

confidence: 99%

“…In heterogeneous natural populations of planktonic organisms, it is challenging to attribute P uptake to different taxonomic groups when using traditional filtration techniques, as their size spectra often overlap and hence do not allow for their unique physical separation (Friebele et al 1978, Nalewajko & Garside 1983, Li & Dickie 1985, Tanaka et al 2004, Duhamel & Moutin 2009. Consequently, most studies on the effect of light on PO 4 3− uptake have been on cultures (Jansson 1993, Donald et al 1997, Riegman et al 2000, Ahn et al 2002, Kumar et al 2009), and those conducted in natural environments have yielded contradictory results (Perry 1976, Reshkin & Knauer 1979, Lemasson et al 1980, Nalewajko & Lee 1983, Nalewajko et al 1986, Litchman et al 2004, Duhamel et al 2006). To our knowledge, the effect of light on DOP utilization has not been assessed in natural microbial assemblages.…”

Section: Introductionmentioning

confidence: 99%

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Light dependence of phosphorus uptake by microorganisms in the subtropical North and South Pacific Ocean

Duhamel¹,

Björkman²,

Karl³

2012

Aquat. Microb. Ecol.

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Light and dark phosphate (PO 4 3− ) uptake rates were investigated in the North Pacific Subtropical Gyre (NPSG) and along a coastal to open ocean transect in the South Pacific Ocean. PO 4 3− uptake rates were consistently higher when incubated in the light, but the ratio of uptake in the light and dark (L:D) decreased with depth. In the NPSG, the L:D ratio of euphotic-layer integrated PO 4 3− uptake was 1.58 ± 0.08 (± SE, n = 15 profiles), and the average L:D ratio was 1.60 ± 0.45 (± SD, n = 42) between 5 and 45 m and 1.25 ± 0.70 (± SD, n = 28) between 150 and 175 m. The L:D ratio was higher for the pigmented plankton-enriched size fractions (0.6 to 2 µm and > 2 µm), but results were difficult to interpret at the oligotrophic stations where non-pigmented and pigmented plankton cell sizes overlapped. Group-specific measurements obtained using flow cytometric cell sorting demonstrated that Prochlorococcus PO 4 3− uptake rates were higher when the samples were incubated under ambient light. Adenosine-5′-triphosphate (ATP) uptake by Prochlorococcus was also higher in the light for the uptake of both the terminal PO 4 3− group ([γ-33 P]ATP) and adenine moiety ([2, 8-3 H]ATP). This could be the result of secondary uptake of PO 4 3− and/or adenine after ATP cleavage by non-pigmented picoplankton. There was no significant difference in P-assimilation by non-pigmented picoplankton between light and dark incubated samples. Light dependence of phytoplankton PO 4 3− uptake could thus influence the functioning of the microbial loop and the flows of matter and energy in marine environments by creating temporal patterns of resource utilization.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Light dependence of phosphorus uptake by microorganisms in the subtropical North and South Pacific Ocean

Duhamel¹,

Björkman²,

Karl³

2012

Aquat. Microb. Ecol.

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“…These results on the role of light fluctuations on nutrient competition are similar to the effects of light fluctuations on competition for light (Litchman and Klausmeier 2001). A recent study (Ahn et al 2002) showed that species-specific light-dependent nutrient uptake affects competitive dynamics in phytoplankton. Light fluctuations of longer time scales, e.g., due to changes in weather, were shown to promote diversity by altering competition for light (Litchman and Klausmeier 2001;Flöder et al 2002).…”

Section: Discussionmentioning

confidence: 99%

Phytoplankton nutrient competition under dynamic light regimes

Litchman

Klausmeier

Bossard

2004

Limnology & Oceanography

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Many physiological processes in phytoplankton, including nutrient uptake, vary on a number of temporal scales. Experiments show that the daily cycle in irradiance affects nutrient uptake rates. We used a Droop-based model of resource competition to investigate how diel variability in nutrient uptake influences phytoplankton competition and community structure. The analytical approximation we derive shows that if nutrient uptake is light dependent, the minimum nutrient requirements and, hence, nutrient competitive abilities depend on light regime in a species-specific way. Consequently, daily variations in irradiance may slow rates of competitive exclusion or reverse the identity of the superior competitor but not allow stable coexistence. Irradiance-induced fluctuations in the maximum nutrient uptake rate of the superior competitor can lead to fluctuations in ambient nutrient concentration and an increase in the average nutrient concentration compared to constant light conditions. This can enhance nutrient use by inferior competitors. These results may be applicable to bacteria-phytoplankton nutrient competition as well. Depending on the costs and benefits of maintaining nutrient uptake in the dark, different strategies of nutrient use are optimal under different light regimes. Our results suggest that by mediating limiting nutrient use, fluctuations in irradiance may alter the structure of phytoplankton communities.In aquatic systems, physical forcing and biotic responses are tightly coupled (Steele and Henderson 1994). Major ecological interactions such as competition and predation are affected by environmental fluctuations. Light is an important environmental factor and an essential resource for phytoplankton that fluctuates on multiple temporal scales. Previously we have demonstrated that daily and seasonal light fluctuations significantly affect phytoplankton competition for light (Litchman and Klausmeier 2001). However, in many aquatic systems phytoplankton compete not for light but for nutrients. A substantial body of literature indicates that nutrient uptake rates depend on many environmental factors including light. It is, therefore, likely that light fluctuations can mediate nutrient competition among phytoplankton. Here we explore how variation in the uptake rates of the limiting nutrient modifies resource competition in phytoplankton.Numerous experimental studies have shown that uptake of many essential nutrients by phytoplankton depends on irradiance. Frequently, the uptake rates are lower in the dark. Riegman et al. (2000) showed that nitrogen (N) uptake of Emiliania huxleyi in the dark was 30% of the uptake rate in the light. Phosphorus (P) uptake in the dark was also lower than in the light, and the greatest difference between the uptake rates was for the lowest growth rate.The maximum nutrient uptake rate (V max ) usually exhibits a much stronger light dependence than the half-saturation

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“…The dilution flow rate was adjusted manually daily to achieve a steady biomass with a target cell density of 10 3 cells mL 21 6 10%. Samples for monitoring and pigment analyses were obtained at the middle of the light phase to avoid effects of diel rhythms (Ahn et al 2002). Pigment sampling details and the highperformance liquid chromatography protocol were carried out exactly as in Leonardos and Harris (2006).…”

Section: Methodsmentioning

confidence: 99%

Physiological steady state of phytoplankton in the field? An example based on pigment profile of Emiliania huxleyi (Haptophyta) during a light shift

Leonardos

2008

Limnology & Oceanography

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A calcifying strain of Emiliania huxleyi was used to study the photoacclimation process during a shift from low (LL) to high (HL) photon flux density (PFD) under nutrient-replete and pH-and [CO 2 ]-controlled continuous cultures. Physiological steady states were obtained after culturing the alga in each PFD for more than a month, and pigment profiles and cell volume changes were monitored for 25 d after the light shift. Fucoxanthin was the major carotenoid in LL, while under HL this role was assumed by 199hexanoyloxyfucoxanthin (19Hex). The photoprotective pigments diadinoxanthin and diatoxanthin (Dd+Dt), normalized to chlorophyll a (Chl a), increased with increasing PFD, while Chl a content per cell and Chl c's and fucoxanthin, normalized to Chl a, decreased with increasing PFD. The sum of all carotenoids normalized to Chl a and the 19Hex+Fuco : Chl c ratio were remarkably constant from LL to HL conditions. The results confirm that the total amount of carotenoids was synthesized/catabolized in tandem with Chl a to a genetically predefined level independent of PFD. When normalized to a per cell basis, Chl a content reached the long-term HL steady state after 17-20 d, while Chl c, Fuco, and Dd+Dt, normalized to Chl a, reached the long-term HL steady state after 5-7 d. Growth rate adjustment was completed within 3 d after the transition to HL. When Chl a was normalized to cellular volume, the transition to a fully acclimated HL state was complete within 3 d. The results highlight the need for the critical evaluation of the normalization ''currency'' (i.e., cell number, volume, Chl a) to which mass is expressed during the photoacclimation process and suggest that natural phytoplankton populations are unlikely to ever be in true physiological steady state.

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DIEL RHYTHM OF ALGAL PHOSPHATE UPTAKE RATES IN P‐LIMITED CYCLOSTATS AND SIMULATION OF ITS EFFECT ON GROWTH AND COMPETITION¹

Cited by 26 publications

References 42 publications

Light dependence of phosphorus uptake by microorganisms in the subtropical North and South Pacific Ocean

Light dependence of phosphorus uptake by microorganisms in the subtropical North and South Pacific Ocean

Phytoplankton nutrient competition under dynamic light regimes

Physiological steady state of phytoplankton in the field? An example based on pigment profile of Emiliania huxleyi (Haptophyta) during a light shift

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DIEL RHYTHM OF ALGAL PHOSPHATE UPTAKE RATES IN P‐LIMITED CYCLOSTATS AND SIMULATION OF ITS EFFECT ON GROWTH AND COMPETITION1

Cited by 26 publications

References 42 publications

Light dependence of phosphorus uptake by microorganisms in the subtropical North and South Pacific Ocean

Light dependence of phosphorus uptake by microorganisms in the subtropical North and South Pacific Ocean

Phytoplankton nutrient competition under dynamic light regimes

Physiological steady state of phytoplankton in the field? An example based on pigment profile of Emiliania huxleyi (Haptophyta) during a light shift

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DIEL RHYTHM OF ALGAL PHOSPHATE UPTAKE RATES IN P‐LIMITED CYCLOSTATS AND SIMULATION OF ITS EFFECT ON GROWTH AND COMPETITION¹