Heterotrophic assimulation and occurrence of dissolved free amino acids in a shallow estuary

• Published in: Marine ecology. Progress series (Halstenbek) Vol. 8; no. 2; pp. 145 - 159
• Main Author: Joergensen, NOG
• Format: Journal Article
• Language: English
• Published: 01-01-1982
• Subjects: Brackish
• ISSN: 0171-8630

Seasonal changes in concentrations of dissolved free amino acids (DFAA), heterotrophic assimilation of the 5 most abundant free amino acids, and release of DFAA from natural populations of phytoplankton were investigated in a shallow estuary on the east coast of Jutland, Denmark. Maximum DFAA concentrations (700 to 900 nM; up to 2471 nM was measured) occurred in spring and autumn, lower concentrations (down to 200 nM) in summer and winter. Heterotrophic assimilation of these amino acids was determined in 3-month intervals at high and low tide, and uptake rates of 0.3 to 23 mu g Cl super(-1) h super(-1) were measured. Serine was preferentially absorbed by microorganisms. Generally, higher uptake rates were found at low tides than at high tides - apparently due to higher numbers of bacteria at low tide, but also influenced by DFAA concentration. A reduced assimilation rate occurred in winter when both temperature and bacterial densities were low.