Release of aminoacids and inorganic nutrients by heterotrophic marine micro-flagellates

Abstract

Heterotrophic microflagellates isolated from the Baltic Sea and grown under laboratory conditions were shown to release dissolved free amino acids (DFAA) when grazing bacteria Flagellates released super(3)H-amino acids when fed super(3)H-leucine-labelled bacteria, and concentrations of amino acids increased in the experimental medium. Serine showed a strong positive correlation with flagellate feeding. Aspartic acid, glutamic acid and ornithine also increased more than other amino acids. During consumption of bacteria, the flagellates released 13% of the ingested nitrogen as ammonia, and 30% of the ingested phosphorus as phosphate. In a field experiment off Scripps Pier, the authors measured bacterial production, flagellate abundance, and concentration of DFAA over a 28 h period. The concentration of DFAA showed a covariation with the flagellate numbers. Results suggest that flagellates may be a source of DFAA in the sea.