Uptake of New and Regenerated Forms of Nitrogen in Primary Productivity1

Abstract

The use of 16N-labeled compounds to obtain specific uptake rates for the various nitrogen sources available to the phytoplankton makes it possible to separate the fractions of primary productivity corresponding to new and regenerated nitrogen in the euphotic zone of the ocean. Measurements of nitrate uptake as a fraction of ammonia plus nitrate uptake have been obtained from the northwest Atlantic and the northeast Pacific oceans. Mean values range from 8.3 to 39.5%, the former being characteristic of subtropical regions and the latter of northern temperate regions or coastal and inland waters. Nitrogen fixation is also a source of new nitrogen. Rates of nitrogen fixation are found to be as high or higher than nitrate uptake, in some cases suggesting an important role for nitrogen-fixing phytoplankton. The role of zooplankton in regenerating nitrogen as ammonia in the Sargasso Sea is examined theoretically. Probably only about IO% of the daily ammonia uptake by phytoplankton is contributed by the zooplankton living in the upper 100 m.

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

“…Nitrogen uptake rates were calculated according to the equations of Dugdale & Goering (1967) and are presented as nitrogen-specific (h-') and absolute (yg-at N 1-' h-') rates. The ratio of nitrogen uptake in the dark bottle (continuous darkness) to that in the light bottle (exposed to the natural light cycle) (V,: V,) is also reported.…”

“…Ammonium and urea regeneration rates (d) have been determined using the approach of Fisher et al (1981). These rates were calculated using the Blackburn-Caperon equation (Blackburn 1979, Caperon et al 1979) d = AP/t + i, where AP = change in concentration of NH: or urea (pg-at N1-') over time interval t (h), and i = nitrogen uptake rate (pg-at N 1-' h-') calculated from 15N accumulation in the particulate matter (Dugdale & Goering 1967). Disappearance uptake rates (Vd) have been calculated from the change in concentration of dissolved nitrogen per unit time (AP/t) and, like the nitrogen-specific and absolute 15N uptake rates (V), are reported for the time intervals over which they have been calculated.…”

“…Regeneration of nitrogen has long been recognized as a possible artifact in determining I5N uptake rates (Dugdale & Goering 1967) and recently it has been shown that these rates may be underestimated by a factor of ca 2 when a constant 15N atom % enrichment is assumed (Glibert et al 1982b). We have not corrected our uptake rates for isotope dilution, as we will now show regeneration of NH: and urea, in these experiments, has little effect on uptake rates calculated with the initial enrichment, however, such a process may dramatically effect the disappearance uptake rates.…”

“…Moreover, most of the nitrogen demands of phytoplankton in nitrogenimpoverished water are supplied by ammonium and urea from regenerative processes, whereas in nitrogen-rich areas nitrogen compounds appear to be utilized at rates proportional to thelr availability (e.g. Dugdale & Goering 1967, McCarthy et al 1977. Experiments using laboratory cultures of phytoplankton have demonstrated that the preconditioning nitrogen substrate affects the response of phytoplankton to the additions of different forms of nitrogen (Horrigan & McCarthy 1981, Dortch & Conway 1984.…”

Stable Isotope Measurement of Ammonium Using HPLC-RTS (high performance liquid chromatography-retention time shift)

“…이를 극복하기 위해서 질소의 안정동위원소 추 적자( 15 N)를 이용하여 각 과정을 측정하는 실험방법이 발달하였다 (Dugdale and Goering, 1967;Blackburn, 1979;Caperon et al, 1979;Lin et al, 2011 (Sigman, 2001;Brandes et al, 2007). 최근 들어 해양환경에서 DNRA (dissimilatory nitrate reduction to ammonium) 나 ANAMMOX (anaerobic ammonium oxidation)와 같은 질소변환 과정이 새롭게 발견되거나 그 중요성이 재평가 받음으로써 암모 늄 안정동위원소 측정의 필요성은 점차 증가하고 있다 (Brandes et al, 2007;Thamdrup, 2012).…”