Description: Standing stock and size composition of the zooplankton comunity (〉100 μm) were studied in four depth strata of the upper 200 m of the water column during a “Meteor” cruise to the central Red Sea and Gulf of Aden in spring 1987. The central Red Sea was divided into a northern area of higher salinity and a less saline southern part. Both areas exhibited significant differences in zooplankton abundance and standing stock. The latter increased by the ratio 1:2:3 from the northern central Red Sea to its southern part and further south to the Gulf of Aden. For size structure analysis samples were fractionated into three size classes (100 to 300, 300 to 500, 500 to 5000 μm). In the central Red Sea the smallest size was dominant whereas in the Gulf of Aden the largest size fraction played a greater relative role than in the central Red Sea. This shift in size structure of the zooplankton community from the Red Sea to the Gulf of Aden is apparently primarily related to ecosystem difference between both areas, leading to a change in species composition. In addition, size reduction of individual species common to both seas may be of some significance in the extreme environment of the Red Sea.

Description: The marine microcopepod family Oncaeidae in the Red Sea has been the subject of comprehensive ecological studies over the past 15 years, providing for the first time insights into their community structure, vertical distribution and feeding ecology. Owing to taxonomic problems in species identification, however, many of the earlier ecological results were based on provisionally named species or morphotypes. A recent, ongoing taxonomic study of Red Sea Oncaeidae resulted in a considerable increase in the estimated numbers of species, since many of the species had not been described before. The present paper focuses on the potential significance of an improved taxonomic resolution of oncaeids with respect to various ecological aspects in this area, such as indicator species, community analysis and vertical distribution. The progress in our knowledge of the diversity of Red Sea Oncaeidae is summarized, including latest findings on the taxonomy and zoogeography of very small species (〈0.5 mm), and the importance of sibling species in the family is pointed out. The south–north gradient in species diversity of Oncaeidae within the Red Sea appears to be greater than previously assumed, since several of the newly described species were restricted to the southern part. The number of endemic species among Red Sea oncaeids is very low, however, most of the new species being also recorded outside the Red Sea. New quantitative data on the abundance and vertical distribution of selected oncaeid siblings obtained during a recent cruise in the northern Red Sea are provided to exemplify the changes in the knowledge of oncaeid community structure attributable to the improved taxonomic resolution. The potential ecological importance of a more differentiated consideration of oncaeid species in marine microcopepod communities is discussed

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: Im August 1966 wurden zwischen Cuxhaven und Edinburgh 39 Oberflachenproben in 10 sm Abstand und 17 Tiefenproben auf 5 Vertikalstationen entnommen. Es wurden die Verteilung von Temperatur, Salzgehalt, Trübung, Gelbstoff-, Chlorophyll a- und Eiweißgehalt und die Artenzusammensetzung des größeren Phytoplanktons untersucht. Folgende Wassermassen wurden beobachtet: 1. Das Wasser der Deutschen Bucht mit hohen Werten für die Trübung, den Gelbstoff-, Chlorophyll- und Eiweißgehalt. Das Phytoplankton ist durch den Reichtum an Diatomeen mit der vorherrschenden Art Rhizosolenia imbricata var. shrubsolei gekennzeichnet. 2. Das salzreiche Doggerbankwasser atlantischer Herkunft, das sehr niedrige Werte für die untersuchten biologischen Faktoren aufweist. Neben den Diatomeen werden Dinoflagellaten häufig. 3. Das Britannische Ostktüstenwasser mit einem leicht erhöhten Gelbstoffgehalt aber sonst ebenfalls sehr niedrigen Werten für Trübung, Chlorophyll a und Eiweiß. Die Kieselalgen sind von Peridineen abgelöst worden. Die Leitform ist Ceratium furca. Der Küsteneinfluß ist an der schottischen Küste sehr viel geringer als in der Deutschen Bucht. Die niedrigen Chlorophyll- und Eiweißwerte in der offenen Nordsee kennzeichnen das sommerliche Minimum in der Planktonentwicklung.

Description: Anhand von zwei käuflichen Präparaten wird die Extinktion von Chlorophyll a in verschiedenen Lösungsmitteln untersucht und daraus der Extinktionskoeffizient für frisch extrahiertes, ungetrocknetes Chlorophyll a in Methanol abgeleitet. Er beträgt für das rote Extinktionsmaximum bei 665 nm 75.0 l/g cm. Die Extinktionskoeffizienten von getrocknetem Chlorophyll a sind in den untersuchten Lösungsmitteln 10-25% niedriger als die von einer frisch extrahierten Chlorophyllösung (Tabelle 2). Die Messung des Chlorophyll a-Gehaltes kann mit hinreichender Genauigkeit in einem Filterphotometer (ELKO II, Zeiss) ausgeführt werden. Hierzu werden Eichkurven für drei verschiedene Interferenzfilter angegeben. From two purchasable preparations of crystalline chlorophyll a, the extinction coefficient of undried chlorophyll a in methanol has been calculated as 75.0 l/g cm at the maximum of extinction at 665 nm. The extinction coefficients of dried chlorophyll a in the different solvents tested are 10-25% lower than those of undried chlorophyll a (table 2). Chlorophyll a can be measured in a filter photometer (ELKO II, Zeiss) with sufficient precision. Standard curves for three different interference filters are given.