Description: Both Podon leuckarti and Evadne nordmanni play a predominant role in the plankton community of Kiel Fjord in summer. Increase and decrease of the populations were recorded through short-term sampling from May to the beginning of July. Abundance in relation to temperature and salinity, body size, number of embryos per female and the occurrence of permanent eggs were investigated. Podon leuckarti reached its peak at the end of May, two weeks earlier than Evadne normanni; the maximum abundance was 6500 individuals · m-3 and 8900 individuals · m-3 respectively. The rapid increase of both populations is characterized by an exponential growth phase. The estimated doubling time ranged from 0.5 to 4.3 days. With increasing temperature, body size and number of embryos per female decreased. An inspection of the stomach content showed that both species apparently had fed mainly on phytoplankton.

Description: The main studies on phytoplankton ecology carried out in Kiel Bight during the last decades are briefly reviewed. Special emphasis is laid on the hydrographical structure of this transitional area between the Baltic Sea and the North Sea, as it strongly affects the seasonal cycle of phytoplankton standing stock and species succession through vertical stratification and advection processes. Both these hydrographical features prevail during the growth period of phytoplankton and are responsible for large variations in population density and nutrient supply. The seasonal species succession is also influenced by advection. The annual primary production figure of about 150 g C·m-2 approaches the upper limit of values recorded for other parts of the western and southern Baltic. Total irradiation appears to exert the strongest influence on the seasonal cycle of primary production as long as water temperatures are low, giving way in summer to temperature as the determining factor for the production rate.

Description: Die Sestonbestimmung hat den Vorteil, eine einfache, vielseitig anwendbare Methode in der biologischen Meereskunde zu sein. Ihre Genauigkeit hängt in erster Linie von der Beschaffenheit des Filtermaterials, der Größe der Filter und den Wägebedingungen ab. In diesem Zusammenhang werden drei Filtersorten miteinander verglichen: Papierfilter (Schleicher & Schüll 575), Sartorius-Membranfilter (SM 11304) und Glasfaserfilter (Whatman GF/C). Die Glasfaserfilter wurden hierbei, soweit bekannt, zum ersten Mal für die Sestonbestimmung benutzt. In der Filtrationsleistung sind sie den Membranfiltern vergleichbar. Aus voneinander unabhängigen Doppelbestimmungen wird die Standardabweichung der Methode bei der Verwendung der verschiedenen Filtersorten ermittelt. Die größte Genauigkeit erreichten Whatman-Glasfaserfilter (⌀ 2,5 cm) mit ± 0,15 mg auf der 95% Wahrscheinlichkeitsebene. Zum Schluß wird eine neue Filtationsapparatur beschrieben und eine ausführliche Arbeitsvorschrift gegeben. Seston determination has the advantage of being a simple method with a wide range of application in biological oceanography. Its accuracy depends mainly on the quality of the filter material, the size of the filters and the weighing conditions. Under these aspects three filter types are compared: paper filters (Schleicher& Schüll 575), Sartorius membrane filters (SM 11304) and glassfibre filters (Whatman GF/C). The glassfibre filters have been used here, as far as is known, for the first time for seston determination. Their filtration efficiency is comparable to that of the membrane filters. By means of independent double determinations the standard deviation of the method shown by the three filter types tested is calculated. The highest accuracy was attained by Whatman glassfibre filters (⌀ 2.5 cm) with ± 0.15 mg on the 95% probability level. Finally, a new filtration apparatus is described and detailed directions for determining seston given.