An experimentally validated nitrate–ammonium–phytoplankton model including effects of starvation length and ammonium inhibition on nitrate uptake

Malerba, Martino E.; Connolly, Sean R.; Heimann, Kirsten

doi:10.1016/j.ecolmodel.2015.08.024

Cited by 12 publications

(9 citation statements)

References 60 publications

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“…Nutrients, in particular nitrate and ammonium, have the greatest potential to limit phytoplankton growth in coastal marine systems (Malerba et al, 2015). For our study regions, nutrient concentrations sampled during the dry season 2013 were much higher in the VDG in comparison to DH: mean ammonium and phosphate concentrations were almost twice those recorded in DH, while nitrate was three times greater in the VDG (Figure 14; Table 4).…”

Section: Phytoplankton: Absorption Coefficients Pigments Cell Countmentioning

confidence: 77%

Bio-Optical Properties of Two Neigboring Coastal Regions of Tropical Northern Australia: The Van Diemen Gulf and Darwin Harbour

et al. 2017

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This study focuses on the seasonal and spatial characterization of inherent optical properties and biogeochemical concentrations in the Van Diemen Gulf and Darwin Harbour, two neighboring tropical coastal environments of Northern Australia that exhibit shallow depths (∼20 m), large (>3 m) semi-diurnal tides, and a monsoonal climate. To gain insight in the functioning of these optically complex coastal ecosystems, a total of 23 physical, biogeochemical, and optical parameters were sampled at 63 stations during three field campaigns covering the 2012 wet and dry seasons, and the 2013 dry season. The total light absorption budget in the Van Diemen Gulf was dominated by nonalgal particles (a NAP ; >45%) during the dry season (May-October) and colored dissolved organic matter (a CDOM ; 60%) during the wet season (November-April). The combined absorption by a NAP and a CDOM generally exceeded ∼80% of the total absorption budget from 400 to 620 nm, with phytoplankton, a Phy , accounting for <20%. In Darwin Harbour, where only the dry season conditions were sampled, the total absorption budget was dominated by an equivalent contribution of a CDOM , a NAP, and phytoplankton. The major processes explaining the seasonal variability observed in the Van Diemen Gulf are resuspension from seasonal south-easterly trade winds in combination with the tidal energy and shallow bathymetry during the dry season months, and mostly terrestrial river runoff during the monsoon which discharge terrestrial CDOM from the surrounding wetlands. Due to light-limited conditions all year round, the particulate scattering coefficient [b p (555)] contributed significantly (90%) to the beam attenuation coefficient c(555), thus strongly limiting phytoplankton growth (Chlorophyll a ∼1 mg.m −3 ). Spatially, the Van Diemen Gulf had higher total suspended solids and nutrient concentrations than Darwin Harbour, with dissolved organic carbon and a CDOM subjected to photobleaching during the dry season. Key bio-optical relationships derived from this comprehensive Blondeau-Patissier et al. Northern Australian Waters' Optical Properties set of parameters, the first ever to be collected in this tropical coastal environment, were successfully used for a region-specific seasonal parameterization a regionspecific seasonally parameterized ocean color algorithm. Challenges related to the parameterization, and the use, of ocean color remote sensing algorithms for these optically complex waters are discussed.

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Section: Phytoplankton: Absorption Coefficients Pigments Cell Countmentioning

confidence: 77%

Bio-Optical Properties of Two Neigboring Coastal Regions of Tropical Northern Australia: The Van Diemen Gulf and Darwin Harbour

et al. 2017

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“…Hence, flux into the quota can be inferred from changes in medium nitrate and ammonium, while flux out of the quota can be inferred from changes in population density (De La Rocha et al . ; Malerba, Connolly & Heimann ; Malerba, Connolly and Heimann ).…”

Section: Methodsmentioning

confidence: 99%

“…The nitrate‐ammonium‐phytoplankton model proposed by Malerba, Connolly and Heimann () was fitted to time series of D. armatus reared in laboratory conditions across treatments of nitrogen types (nitrate, ammonium, or both) and N‐history (N‐replete or N‐deplete). The model followed the general assumptions of the original “Quota” model, first proposed by Droop (): cells take up nitrogen from the environment and divide at a cell‐specific rate that is proportional to their internal nitrogen quota.…”

Section: Methodsmentioning

confidence: 99%

“…Quota dynamics were not experimentally measured but were instead inferred from the model fits: all of the parameters that influence the dynamics of the unobserved internal quota (Q (t)) also appear in the equations for the observed dynamics for nitrate depletion and biomass growth. Hence, flux into the quota can be inferred from changes in medium nitrate and ammonium, while flux out of the quota can be inferred from changes in population density (De La Rocha et al 2010;Malerba, Connolly & Heimann 2012;Malerba, Connolly and Heimann 2015).…”

Section: O D E L C a L I B R A T I O Nmentioning

confidence: 99%

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Nutrient utilization traits vary systematically with intraspecific cell size plasticity

2016

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Summary Trait‐based approaches are increasingly used to help understanding community structure and ecosystem functioning. A large proportion of trait‐based studies define a species by its mean trait values and assume intraspecific trait variability to be negligible compared to interspecific differences. However, this assumption is rarely tested. Phenotypic cell size plasticity can be particularly important in phytoplankton species, which are known for their rapid changes in cell size in response to variations in environmental conditions. While phytoplankton traits show clear systematic trends with mean cell size across species, how size‐related plasticity influences the dynamics of a species remains unknown. In this study, we evaluate the effects of cell size plasticity on the nitrogen (N) utilization traits of the green alga Desmodesmus armatus (Chlorophyta), reared in different inorganic nitrogen sources (nitrate, ammonium or both) and nutrient histories (N‐replete and N‐deplete). Results show that traits for per‐cell ammonium uptake, maximum cell growth rate and minimum N‐quota change substantially within the study species, depending on mean cell size and nutrient history. In contrast, per‐cell nitrate uptake was independent of cell size. These results indicate that representing phytoplankton species only by their mean trait values could underestimate the physiological performance of a species by as much as one order of magnitude. This study highlights the extent to which explicit incorporation of within‐species trait variability can enhance our understanding of how species performance changes along environmental gradients. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12662/suppinfo is available for this article.

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“…Nitrate and ammonium are the most abundant nitrogen sources that phytoplankton utilize for their growth and metabolism: approximately 40% of global primary production is the result of assimilating these two nitrogenous nutrients by phytoplankton 1 . Even so, nitrogen is a limiting nutrient for phytoplankton in many marine environments and its acquisition and assimilation is highly regulated.…”

Section: Introductionmentioning

confidence: 99%

Expression of novel nitrate reductase genes in the harmful alga, Chattonella subsalsa

Wang

Bouchard²,

Coyne

2018

Sci Rep

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Eukaryotic nitrate reductase (NR) catalyzes the first step in nitrate assimilation and is regulated transcriptionally in response to external cues and intracellular metabolic status. NRs are also regulated post-translationally in plants by phosphorylation and binding of 14-3-3 proteins at conserved serine residues. 14-3-3 binding motifs have not previously been identified in algal NRs. A novel NR (NR2-2/2HbN) with a 2/2 hemoglobin domain was recently described in the alga Chattonella subsalsa. Here, a second NR (NR3) in C. subsalsa is described with a 14-3-3 binding motif but lacking the Heme-Fe domain found in other NRs. Transcriptional regulation of both NRs was examined in C. subsalsa, revealing differential gene expression over a diel light cycle, but not under constant light. NR2 transcripts increased with a decrease in temperature, while NR3 remained unchanged. NR2 and NR3 transcript levels were not inhibited by growth on ammonium, suggesting constitutive expression of these genes. Results indicate that Chattonella responds to environmental conditions and intracellular metabolic status by differentially regulating NR transcription, with potential for post-translational regulation of NR3. A survey of algal NRs also revealed the presence of 14-3-3 binding motifs in other algal species, indicating the need for future research on regulation of algal NRs.

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An experimentally validated nitrate–ammonium–phytoplankton model including effects of starvation length and ammonium inhibition on nitrate uptake

Cited by 12 publications

References 60 publications

Bio-Optical Properties of Two Neigboring Coastal Regions of Tropical Northern Australia: The Van Diemen Gulf and Darwin Harbour

Bio-Optical Properties of Two Neigboring Coastal Regions of Tropical Northern Australia: The Van Diemen Gulf and Darwin Harbour

Nutrient utilization traits vary systematically with intraspecific cell size plasticity

Expression of novel nitrate reductase genes in the harmful alga, Chattonella subsalsa

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