AMINO-ACID-COMPOSITION OF SEAWATER AND DISSOLVED HUMIC SUBSTANCES IN THE GREENLAND SEA

The amino acid composition of filtered seawater and dissolved organic matter fractionated with XAD-2 resin was measured in samples from the Greenland Sea. Glycine, aspartic acid, glutamic acid, alanine, and serine made up ca. 80% of the total dissolved amino acids (TDAA) in the unfractionated seawater samples and XAD-fractions. Glycine was predominant, accounting for 28% of TDAA in seawater, 41 % in the hydrophobic acid (HbA) fraction and 45% in the hydrophobic neutral (HbN) fraction. TDAA concentrations in the hydrophylic (H1) fraction correlated significantly with chlorophyll a, whereas no significant relationship was found between chlorophyll and TDAA or the individual amino acid composition in HbA and HbN. TDAA values of 150-250 nM are assumed to be present as part of refractory compounds throughout the water column. At depths of about 1000-1500 m almost 100% of TDAA in seawater is found in the ''humic'' fractions HbA and HbN. On the average TDAA accounted for ca. 24% of the organic nitrogen content in HbN and about 7% of the nitrogen in HbA and H1 fractions, respectively.