Nitrogen assimilation by phytoplankton and other microorganisms in the surface waters of the central North Pacific Ocean

✍ Scribed by R. W. Eppley; J. H. Sharp; E. H. Renger; M. J. Perry; W. G. Harrison

• Publisher: Springer-Verlag
• Year: 1977
• Tongue: English
• Weight: 835 KB
• Volume: 39
• Category: Article
• ISSN: 0025-3162
• DOI: 10.1007/bf00386996

✦ Synopsis

Assimilation rates of 15N-labelled ammonium, urea, and nitrate by plankton in the upper euphotic zone were measured in 2 summer, 2 winter, and I spring cruise in the central North Pacific Ocean. Average rates of ammonium plus urea assimilation could not be determined precisely, but were estimated to be 7 to 25 ~g-at. N m-3 day-1. Indirect evidence suggested that non-photosynthetic microorganisms contributed to these rates. Nitrate assimilation was negligible in the upper waters considered in this report (above the chlorophyll maximum and the nutricline). Potential, nitrate-saturated rates were in the range I to 8 ~g-at. N m-3 day-1. Seasonal comparison showed lowest rates of both carbon and nitrogen assimilation rates per chlorophyll a in winter.