NITROGEN ASSIMILATION OF AN OCEANIC DIATOM IN NITROGEN‐LIMITED CONTINUOUS CULTURE¹

Abstract

SUMMARY The oceanic diatom Thalassiosira pseudonana Hasle and Heimdal (formerly Cyclotella nana) was grown with 12L:12D illumination cycles in nitrogen‐limited continuous culture with a mixture of ammonium and nitrate as the N source. Measurements included, at 3 different growth rates (degrees of N limitation), cell concentration, cell carbon, nitrogen, and chlorophyll a contents, cell volume, photosynthetic carbon assimilation vs. irradiance, short‐term uptake of ammonium and nitrate vs. their ambient concentrations, and in vitro activities of the assimilatory enzymes nitrate reductase and glutamic dehydrogenase. The various parameters showed either an increase (pattern a) or a decrease (pattern b) with increasing N limitation. Those following pattern a were nitrate reductase activity and the capacity to assimilate nitrate and ammonium. Those following pattern b were glutamic dehydrogenase activity, photosynthetic rate, nitrogen:carbon and chlorophyll a:carbon composition ratios. Results are discussed in terms of the interpretation such measurement for natural phytoplankton and effects of circadian periodicity.

Time course of uptake of inorganic and organic nitrogen by phytoplankton in the Strait of Georgia: comparison of frontal and stratified communities

“…Simultaneous utilization of NH: and NO; is well documented (Collos & Lewin 1974, Eppley & Renger 1974, Bienfang 1975, Conover 1975, Caperon & Ziemann 1976, Conway 1977, Maestrini et al 1982) and our results not only demonstrate dual nitrogen substrate utilization but that NH:, NO; and urea may be taken up concurrently. As pointed out by Collos (unpubl.)…”

Effects of temperature, nitrogen, and light limitation on the optical properties of the marine diatom Thalassiosira pseudonana

“…For example, the U-shaped pattern of cellular carbon and nitrogen, the linear pattern of increasing C : N, and the general trend of Chl a to increase and C : Chl a to decrease with increasing temperature were observed by Thompson et al (1992). The reduction in nitrogen and Chl a quotas accompanied by an increase in C : N and C : Chl a ratios for T. pseudonana grown either under N limitation or saturating light is also well documented (Eppley and Renger 1974;Berges and Harrison 1995;Reynolds et al 1997).…”

Fluctuations in the Organic Carbon to Chlorophyll a Ratios for Estuarine Benthic Diatom Populations

“…In nearly all cases there is a reasonable increase in the C/Chl-a ratio caused by a decrease of cell chlorophyll a and increase of cell carbon. Only Eppley and Renger (1974) reported a cell carbon decrease while Thomas and Dodson (1972) found changing cell carbon levels. It is remarkable that the phenomenon of CIChl-a increase appears regardless of the kind of limiting nutrient.…”

“…Steele and Baird (1962), Antia et al (1963), Coombs et al (1967), Eppley (1968), Strickland et al (1969), Hobson and Pariser (1971), Thomas and Dodson (1972) and Peny (1976) showed that deficiency of P, N and Si could lead to a considerable increase in the organic carbon to chlorophyll a ratios. Caperon and Meyer (1972), Eppley and Renger (1974) and Perry (1976) described a negative correlation between specific growth rate and the organic carbon to chlorophyll a ratio. A list of the data available is given in Table 2.…”

“…Parsons & Strickland (1959) 39.6 Antia et al (1963) 25 Eppley (1968) 22.2-47.5 Eppley et al (1971) 60 Eppley et al (1977) 10-90 Antia et al (1963) 23.5-114 Induced bloom; mixture of 6 diatoms and 1 dinoflagellate Coombs et al (1967) 23.5-29.6 Si-deficiency; Navicula pelliculosa phytoplankton Eppley (1968) (22.2-47.5)-No detectable N;natural population, (71.4-125.0) open sea, composition unknown StricMand et al (1969) 34.5-83.3 N limitation; deep tank population of Caclonia niei Hobson & Pariser (1971) 14.7-100.0 NO, deficiency; Thalassiosira fluviatilis Caperon & Meyer (1972) 55.0-500.0 N limitation; chemostat culture of nalassiosira pseudonana Thomas & Dodson (1972) 19.0-61.8 N limitation; chemostat culture of Chaetoceras gracilis Eppley & Renger (1974) N and P limitation; chemostat culture (1976) 28.6-91.4 of 72alassiosira pseudonana chlorophyll a ratios also hold for benthic diatom population~. Therefore, organic carbon to chlorophyll a ratios were determined for intertidal mobile benthic diatom populations.…”