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

Patricia M. Glibert (Lead / Corresponding author), Frances P. Wilkerson, Richard C. Dugdale, John A. Raven, Christopher L. Dupont, Peter R. Leavitt, Alexander E. Parker, Joann M. Burkholder, Todd M. Kana

    Research output: Contribution to journalArticlepeer-review

    260 Citations (Scopus)

    Abstract

    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 NH4+. Long thought to be the preferred form of N for phytoplankton uptake, NH4+ may actually suppress overall growth when concentrations are sufficiently high. NH4+ has been well known to be inhibitory or repressive for NO3- uptake and assimilation, but the concentrations of NH4+ that promote vs. repress NO3- 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 NH4+ and NO3- 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 NO3-/ NO2- reduction to NH4+ and photorespiration that may lead to growth suppression are highlighted. While more is known about diatoms, taxon-specific differences in NH4+ and NO3- 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.

    Original languageEnglish
    Article number10203
    Pages (from-to)165-197
    Number of pages33
    JournalLimnology and Oceanography
    Volume61
    Issue number1
    Early online date11 Oct 2015
    DOIs
    Publication statusPublished - Jan 2016

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