Fahrtbericht über die Reise 100/a der "Poseidon" [POS100/a] in die Gewässer westlich der Lofoten

Die Reise 100 der "Poseidon" wurde durchgeführt im Rahmen der von der Deutschen Forschungsgemeinschaft geförderten Pilotstudie zur möglichen Errichtung eines neuen Sonderforschungsbereiches an der Universität Kiel mit dem Thema "Sedimentation in borealen Meeren". Ziel der Pilotstudie ist es, die Grundlagen für ein interdisziplinäres Projekt vorzubereiten, das die komplexen Zusammenhänge zwischen physikalischer Umwelt, biologischer Produktion, Sedimentation aus dem pelagischen System und die Abbildung pelagischer Prozesse im und auf dem Meeresboden in der Norwegischen See erforschen soll. Ziel der Reise 100a der "Poseidon" war es, in ausgewählten "Stationsboxen" von 1ox1o sm Kantenlänge die Sedimentation von Phytoplankton nach einer Blüte zu messen, und die Wassermassenverteilung in Zeitskalen von Tagen in einer in Stromrichtung nach Norden ausgerichteten "Box" zu beschreiben

Productivity regime and phytoplankton size structure in the tropical and subtropical North Atlantic in spring 1989

Productivity regime and phytoplankton size structure are described for two different epipelagic systems in the tropical/subtropical Northeast Atlantic Ocean investigated during 9–11 day drift studies in spring 1989 in the JGOFS North Atlantic Bloom Experiment, 18°N, 30°W and 33°N, 20°W. At the 18°N study site, an oligotrophic system was encountered. The water column above the main pycnocline at about 50–60 m depth was nutrient-depleted, and both chlorophyll and primary production displayed subsurface maxima at the nutricline. Picoplankton was the dominant size fraction, accounting for 78–90% of chlorophyll and 83–98% of primary production. Synechococcus-type coccoid cyanobacteria were the dominant picoplankters. The hydrographic situation was characterized by high small-scale variability; the most interesting feature was the intrusion of nutrient-depleted Subtropical Salinity Maximum Water into the euphotic zone, whose impacts on the productivity regime are discussed. At 33°N study site, a post-bloom situation was encountered. Although the euphotic zone was nutrient-depleted, higher amounts of larger phytoplankton were present, the contribution of picoplankton being 42–53% of chlorophyll and 42–86% of primary production. Over the course of the drift study, subsurface maxima of chlorophyll and productivity evolved, the contribution of picoplankton having increased. Picocyanobacteria again were the dominant picoplankters. At both study sites the profiles of abundance ratios of picocyanobacteria to picoeucaryotes cell numbers proved to be a useful tool to characterize water masses

Productivity regime and phytoplankton size structure in the Arabian Sea

The productivity regime and size structure of phytoplankton are described for three different epipelagic systems in the Arabian Sea during the inter-monsoon period in spring 1987: (1) the coast of Oman; (2) the central Arabian Sea; and (3) the shelf off Pakistan. These results are related to the functioning of the specific ecosystem. Off the coast of Oman, the transition from a surface maximum of autotrophic biomass and production to a more oligotrophic system, with a chlorophyll subsurface maximum, was observed. Concomitantly, the size spectrum changed towards a higher significance of picoplankton. In the central Arabian Sea, a typical oligotrophic system with a pronounced subsurface maximum of autotrophic biomass and primary production was encountered. Here, the epipelagic system could be divided into two distinct sub-systems: the surface layer “regenerated” production, the predominance of picophytoplankton and minor losses due to sedimentation, thus a “closed” system; and the subsurface maximum layer at the nutricline characterized by higher sedimentation losses and more diatoms. Both sub-systems showed about the same productivity, the turnover in the surface layer having been much greater than in the subsurface maximum. The system on the shelf off Pakistan is seen as a decay stage of the open ocean system when water from offshore is transported onto the shelf during the onset of monsoon winds

Sedimentation of particulate matter during a phytoplankton spring bloom in relation to the hydrographical regime

Data presented and discussed here were collected continuously during April/May 1975 in the Bornholm Basin of the Baltic Sea. Sedimentation rates of particulate matter were recorded with 5 multisample sediment traps from different depths in the water column at 2 positions 170 km apart. Current meter data collected during the same period and depths indicated that the positions remained hydrographically distinct during the investigation. Particulate matter from the euphotic zone including diatom cells formed the bulk of the material collected by all traps. This flux of organic particles to the bottom was unimpeded by the strong density stratification present in the water column. The upper traps always collected less material than lower ones. This paradox has been ascribed to diminishing current speeds with depth, concomitant with an increase in sinking rates of phytoplankton and phytodetritus. Both factors influence the sampling efficiency of sediment traps, which are thought to have underestimated actual sedimentation rates here. A time lag of 2 to 3 weeks in bloom development seemed responsible for the characteristic differences between the two positions. The phase of major sedimentation at one position covered about 18 days, and a distinct sequence in the composition of the material collected by the 6 glasses of each trap indicated phases of a progressively deteriorating phytoplankton population in the water column contributing the particulate material. A total of 6.2 g C m-2 in 34 days was recorded at this station. Apart from a trap situated in an oxygen deficient layer which collected 0.44 g C m-2 of zooplankton corpses, zooplankton mortality was overestimated by the traps. Large-scale sedimencation of “fresh” organic matter produced by the spring bloom is probably a regular feature in areas with low over-wintering zooplankton populations and, as such, possibly has a direct stimulatory effect on growth and reproduction of the benthos

Zur Bestimmung des Extinktionskoeffizienten für Chlorophyll a in Methanol

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

Der Kranzwasserschöpfer, ein neuentwickeltes Gerät zur gezielten Probennahme

Es wird ein Geräit beschrieben, mit dem man sechs 5-Liter-Wasserproben aus beliebigen Wassertiefen entnehmen kann. Die Schöpfer werden elektromagnetisch geschlossen. Durch Zusatzgeräte lassen sich verschiedene Parameter kontinuierlich registrieren (z. B. t° C, S ‰, Tiefe, Oberlicht, Lichtextinktion). Dies ermöglicht je nach Fragestellung eine gezielte Probennahme. An apparatus is described which makes it possible to obtain six 5-liter walersamples from arbitrary depths. The waterbottles are closed electromagnetically. By means of accessory apparatus various parameters can be registered continuously (e.g. t°, S ‰, depth, downward light, lightextinction). This will make it possible to take samples at representative depths, which are most relevant to the problem under investigation