Utilizatin of Organic Nitrogenous Compounds as Nitrogen Source by Mrine Phytoplankton

Abstract

The ability of photosynthetic diatoms to utilze organic nitrogenous substances in the light was investigated to clarify the physiological characteristics of phytoplankton which was employed as the biological indicator organisms in the eutrophic level as proposed by the authors.
Skeletonema costatum collected at Dokai Bay and ranked as an indicator species of extremely eutroohic level was able to use peptone, trypticase, and urea. Further this species was capable of using several amino acids among twenty two amino acids tested. In this species, arginine and glutamine were excellent nitrogen sources as well as nitrate, followed by glutamate, aspartic acid, and tryptophan in somewhat low order. On the other hand, three indicator organisms ranked as eutrophic species such as S. costatum collected at Suho Nada, and Chaetoceros curvisetus and Eucampia zoodiacus could scarcely utilize organic nitrogenous compounds except urea, as a sole nitrogen source.
The heterotrophic capability of S. costatum which ranked as an extremely eutrophic species appears t be an important factor towards growth under an environmental condition polluted by domestic and industrial effluents.