REFRACTORY ORGANIC-COMPOUNDS IN POLAR WATERS - RELATIONSHIP BETWEEN HUMIC SUBSTANCES AND AMINO-ACIDS IN THE ARCTIC AND ANTARCTIC

A synopsis of data on the amino acid compositions of Arctic and Antarc tic seawater, XAD-fractions of dissolved organic matter (DOM) and susp ended particulate organic material (POM) is presented. Total dissolved amino acids (TDAA) correlated highly significantly with dissolved org anic nitrogen (DON), representing about 11% of DON in unfractionated f iltered seawater. Average DON values were similar with ca. 3-4 mu M N in the Arctic and Antarctic. Differences in amino acid distribution an d composition patterns in particulate and dissolved material suggest t he selective preservation or utilization of certain amino acids. In PO M, glycine, alanine, glutamic acid, aspartic acid and serine made up c a. 50% of the total, while the same amino acids represented 70-80% of TDAA in unfractionated seawater and in the ''humic'' XAD-fractions. Th e mole percentage of glycine increases from POM (8%) to bulk filtered seawater (27%), reaching 33-45% in the hydrophobic neutral (HbN), alco hol-soluble fraction of DOM. Evidence is presented for a selective uti lization of aspartic acid and its enrichment in the non-humified fract ion of DOM. In both regions, at the surface ca. 60%, and at depths >50 0 m almost 100% of TDAA is found in the ''humic'' fractions. A backgro und value of TDAA of around 200 nM, mostly contained in the HbN fracti on, is present throughout the water column, probably forming part of r ecalcitrant molecules. The relation of these findings to different hum ification mechanisms is discussed.