K. Eberlein

Development of lipids during a spring plankton bloom in the northern North Sea: I. Particulate fatty acids

Abstract The plankton spring bloom in the northern North Sea was extensively investigated during a period of three months in 1976 at a fixed station occupied by the R.V. “Meteor”. Samples of different depth-profiles, representative of the phytoplankton development, were collected eleven times to analyze the concentration of fatty acids of the particulate matter. The water column was divided into an upper and lower layer according to the thermocline depths, because different processes take place in these layers. During the exponential growth phase the fatty acid concentration rose only slightly due to increases in polyunsaturated fatty acids (18:4, 20:5, 22:6), which are typical for marine plankton. With the exhaustion of nutrients the biochemical composition changed and the fatty acid concentration increased sharply from about 3 to 20 μmol C dm − finally to about 30% of the particulate carbon. The main proportion consisted of oleic acid (28.3%) and palmitic acid (24.2%). The first phytoplankton bloom, dominated by diatoms (Chaetoceros species), was characterized by the increase in fatty acids with 16 carbon atoms, whereas during the second smaller bloom, with dinoflagellates as the main species, more fatty acids with 18 carbon atoms occurred. After the stationary growth phase the phytoplankton biomass strongly decreased, resulting in an increase of particulate matter below the thermocline. The fatty acid pattern there was similar to that during the stationary phase of the phytoplankton bloom in the upper layer.

Parallel plastic tank experiments with cultures of marine diatoms

The reproductibility of tank experiments concerning unicellular marine algal development was analyzed by means of parallel experiments with cultures ofThalassiosira rotula andSkeletonema costatum, using large flexible plastic tanks under semi-natural conditions. The tanks (3–4 m3, 4–5 m deep) were exposed in the German Bight at a station in the outer harbour of helgoland. The water was obtained from the open North Sea in towable tanks; it was filtered (plate filter), enriched with nitrate (20–30 μgat dm−3), phosphate (1.3–2.3 μgat dm−3) and silicate (15–23 μgat dm−3)-nearly natural springtime concentrations in this area-and inoculated with 103–105 cells dm−3. The water was mixed with non-metal stirring equipment. Within 5 days, concentrations of 106–107 cells dm−3 in an exponential growth phase were obtained. In experiments withT. rotula a parallel development was achieved in spite of some contamination by surrounding water. This is the case for nearly all parameters analyzed (nutrient salts, phytoplankton, bacteria, C, N and particulate carbohydrates). The heterotrophic bacteria, which were determined by means of the plate method, reached concentrations of up to 106 (T. rotula) and 105 (S. costatum) CFU cm−3, respectively. They showed a consistent retrograde development at diatom concentrations above a certain level. The crop did not increase again until the diatoms had reached the stationary phase. During exponential growth ofT. rotula (G=8.9–11.7 h) a partially synchronous cell division was observed. There were also rhythms with respect to cell size (pervalvar axes) and chain length (number of cells). For the experiments withS. costatum (G=10–11.4 h) diurnal variations of cell size and chain length occurred. The present results indicate acceptable reproducibility of algal development and related phenomena in enclosed water bodies.

River Input of Nutrients into the German Bight

In the present paper we discuss the relationship between nutrient discharge and eutrophication conditions in the German Bight during summer. Nutrient inputs into this area are controlled by the discharge rates of, and the biological processes in its major nutrient supplier — the river Elbe. The shape and direction of the nutrient plume are modulated by wind stress. Eutrophication conditions were inferred from oxygen deficiency associated with remineralization in cold bottom layers in areas deeper than 20 m. Thermocline breakup appeared only following 4 days periods of wind forces > 7 Bft. By repeated investigations of the same station grid within 4 days, high variability of nutrient gradients is documented.

Release of Dissolved Organic Substances in the Course of Phytoplankton Blooms

Organic matter in the sea represents a continuous size spectrum, beginning with free, small molecules, macromolecules, colloids and aggregates and ending with planktonic organisms. By arbitrary definition, the fraction passing filters with pore sizes of 0.5 to 1.0 μm is defined as the dissolved fraction (Williams 1975). This fraction constitutes by far the major part of organic matter (DOM) in the sea (Mopper and Degens 1979, Cauwet 1981), more than 60% of which is still unidentified.

Parallel experiments with Thalassiosira rotula in outdoor plastic tanks: Development of dissolved free amino acids during an algae bloom

Three outdoor plastic tanks were filled with North Sea water. The water was filtered free of algae and inoculated with the diatom Thalassiosira rotula. Under nearly natural nutrient supply an exponential plankton growth occurred with realistic cell concentrations. The flexible tanks (3–4 m3, 4–5 m deep) were exposed in the German Bight at a station in the outer harbour of Helgoland. The concentration changes of dissolved free amino acids (DFAA) were determined. The direct determination method applied permitted an analysis in picomole range without loss and with good reproducibility. The preliminary concentration of DFAA amounted to 0.2 μmol dm−3 in all three cultures, increasing during the development of T. rotula to 0.9–1.3 μmol dm−3 and decreasing in the stationary phase back again to smaller values. A high degree of temporal variation in DFAA was observed in all three cultures. In spite of these rapid changes in concentration, a good parallel development could be shown for all cultures, which extended as far as the spectra of the amino acids. Relationships between DFAA and other parameters of the culture-systems were examined.

Fluctuations of Dissolved Amino Acids: A Comparison of Natural and Enclosed Phytoplankton Populations in the North Sea

Cumulative production of dissolved organic material (DOM) from the classical food web containing phytoplankton excretion, losses during grazing, and Zooplankton excretion, was estimated to amount to about 60% of primary production (Williams 1981). A good part of this material is in a steady state of release and heterotrophic uptake by the various members of a plankton community. Because of the intricate interactions, little is known about the fate of these substances. Results from laboratory experiments are of limited use and sometimes misleading (Hellebust and Guillard 1967; Sharp 1977). On the other hand, investigations in the open sea are more complicated considering the hydrodynamic influences.

Composition of Natural Surface Films in the North Sea

The appearance of surface films, so-called “slicks”, is an often observed phenomenon. Besides the articial surface films, which are caused by man made pollutions, e.g. oil spills from ships or oil accidents, natural surface films can result from dissolved and particulate organic substances released by the organisms of this biotope. Due to the large amount of dissolved organic matter in sea water, natural surface films can be formed spontaneously on the sea surface, if wind velocity is below about 3 Bft. Waves and turbulences caused by stronger wind forces will mix surface and subsurface waters.

Thin-layer chromatography of red cell glycosphingolipids from various mammalian species

Abstract Two thin-layer chromatography systems for the separation of glycosphingolipids from total lipid extracts of erythrocytes were developed. By system I (Silica Gel HR-magnesium silicate (4:1)/tetrahydrofuran-water (5:1)), ceramide hexosides were separated from all other lipids and fractionated into mono-, di- and triglycosyl ceramides. By system II (Kieselguhr G, impregnated with a 0.60 M boric acid-0.15 M disodium tetraborate buffer (pH 7.9)/chloroform-methanol-water (65:25:4)), complex glycosphingolipids (mucolipids) were separated from all other lipids and fractionated. The red cells of nine different mammals showed no species variation in the qualitative composition of the ceramide hexosides but a marked variation in the mucolipid composition as well as in the concentration of the glycosphingolipids.