Natürliche Oberflächenfilme im Seegebiet vor Sylt

The physical and chemical properties of the sea surface can be altered considerably by the formation of slicks and the accumulation of particles (including plankton). Investigations of natural slicks near the island of Sylt consisted of analyses of the dissolved and particulate surface-active substances, as well as the identification of plankton and bacteria collected by a surface-film sampler. The analyzed surface material consisted primarily of phytoplankton (Prorocentrum micans in particular), bacteria, detritus and dissolved compounds of fatty acids. These fatty acid compounds alone would not account for the slick. The slick appeared to be caused by the calm weather, the active accumulation of P. micans at the surface, and the increase in bacteria associated with this accumulation. Here a decrease was observed in the dissolved surface-active substances compared with the concentration usually found in normal surface waters, of which the total fatty acid content in a sample was taken as indicator. In some cases a correlation was found between fatty acids and particulate matter in naturally occurring slicks. Particularly large variations were found in the fatty acid patterns in the filtrate and filter residue at a time when no slick was present and no particulate matter had accumulated at the surface.

---

---

Diese Arbeit wurde von der Deutschen Forschungsgemeinschaft im Rahmen des SFB 94, Hamburg, unterstützt.     

The development of a natural plankton population in an outdoor tank with nutrient-poor sea water. I. Phytoplankton succession

Due to complex hydrodynamic and biological inhomogeneities, the phytoplankton species succession cannot be satisfactorily observed, apart from the seasonal blooms which occur in temperate waters. Large flexible plastic tanks have proved to be useful for such observations. In 1972, for 28 days, a phytoplankton succession in nutrient-poor water in the outer harbor of Helgoland was observed in a flexible plastic tank (3 m³). During this period, 3 phytoplankton biomass maxima were formed with many significant correlations. In the first 7 days the ammonia concentration decreased from over 6 to 2 mol 1^-1 for 14 days. The nitrate concentration remained in the range of 3–6 mol 1^-1 and then fell abruptly to 0–2 mol 1^-1. The phosphate concentration was about 0.1 mol 1^-1. Lauderia borealis dominated the first period, and its increase was significantly correlated with the decrease in ammonia. The diatom was succeeded by two dinoflagellates, Dinophysis acuminata and Prorocentrum micans. The last period of the experiment was characterized by a stronger development of Rhizosolenia species. The rapid recovery of the crop in the nutrient-poor water points to intensive remineralization processes. The irregular occurrence of ammonia near the surface was correlated with the appearance of Noctiluca miliaris at this depth. It is expected that repetitions of this type of experiment will permit further explanations of statistical correlations which are not yet clear. As a first step, in order to test hypotheses, a correlation analysis was employed to eliminate the statistically non-significant correlations.This work was supported by the Sonderforschungsbereich 94, Hamburg, of the Deutsche Forschungsgemeinschaft.