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Effects of light and ammonium on nitrate uptake by two species of estuarine phytoplankton
Author(s) -
Bates Stephen S.
Publication year - 1976
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1976.21.2.0212
Subject(s) - ammonium , nitrate , phytoplankton , photosynthesis , light intensity , botany , respiration , saturation (graph theory) , ammonium nitrate , chemistry , biology , environmental chemistry , nutrient , ecology , physics , mathematics , organic chemistry , combinatorics , optics
The incident light intensity, preconditioning light history, and the presence or absence of ammonium affected the rate of nitrate uptake by a chlorophyte and Skeletonema costatum isolated from the Hudson estuary. In the absence of ammonium, shade‐adapted cells reached the highest maximum velocity of nitrate uptake ( V max ). Skeletonema costatum had a lower half‐saturation constant for light ( K LT ) than the chlorophyte and reached a greater V max . In the presence of ammonium, nitrate uptake was depressed at all light intensities, but more in shade‐adapted than in sun‐adapted cells of both species, and more in S. costatum than in the chlorophyte. The V max for ammonium was greater in shade‐adapted than in sun‐adapted cells. Since nitrate and ammonium uptake were related to the Chl a content of the cell, energy for uptake was probably derived primarily from photosynthesis in the light but may also be derived from respiration since substantial dark uptake was observed, especially in S. costatum.