Gelöste Aminosäuren in Oberflächenwasser der Nordsee bei Helgoland: Konzentrationsveränderungen im Sommer 1970

In order to obtain additional information on changes in dissolved amino-acid content of the surface water of the North Sea, more than 30 water samples taken near Helgoland (54/11.3′ N; 7/54′ E) between April and October, 1970, were investigated. The method was the same as reported by Bohling (1970). In addition to free amino acids in a number of cases, also that fraction of combined amino acids was analyzed which passed a cation exchange column in H⁺ form. The average concentration of free amino acids was higher in 1970 than in 1969, reaching a total maximum of 6 μM/l at the end of May. The amino-acid content fluctuated considerably even over short periods of time. The relative amounts of single compounds, however, remained rather constant. During Summer, 1970, the relationship between the concentrations of free and “combined” amino acids varied. As far as can be judged from the limited number of analyses, combined amino acids increased with the phytoplankton mass; such increase was not observed in the free amino acids. A possible explanation of the results, based on microbial activity, is discussed.