Tagesgang eines Myctophiden (Pisces) und zweier von ihm gefressener Mollusken des Neustons

Neben Evertebratenplankton und Jungfischen anderer Arten wurden 25 Myctophiden der Art Centrobranchus nigroocellatus im April und Juli 1967 im Seegebiet westlich und südwestlich von Madeira mit einem Neustonnetz gefangen. 21 C. nigroocellatus hatten ausschließlich Mollusken, davon 18 nur die Gastropoden Styliola subula und Atlanta peroni gefressen. Der Myctophide und die Gastropoden steigen zeitweise in die 0-10 cm-Mikroschicht auf: Sie sind nachtpositiv mit Betonung der Abenddämmerung bei S. subula, mit Betonung der Morgendämmerung bei Atlanta peroni und mit Betonung wahrscheinlich beider Dämmerungen bei C. nigroocellatus. Der Myctophide zeigt mit der Nahrungsspezialisierung zusammenhängende morphologische Besonderheiten. With a neuston-net 25 Centrobranchus nigroocellatus were collected west of Madeira during April and July 1967. The guts of 18 myctophids contained exclusively the gastropods Styliola subula, Atlanta peroni, or both of them. The myctophid and both of the gastropods were found in the 0-10 cm-microlayer at night. S. subula was most abundant at dusk, A. peroni at dawn, whereas C. nigroocellatus was caught most frequently during dusk and dawn. Adaptions of the myctophid are discussed

Trophic relationships of zooplankton in the eastern Mediterranean based on stable isotope measurements

Abundance and stable isotope composition of large and small mesozooplankton were analyzed in samples taken with 333 and 100 μm nets, respectively, at four sites in the eastern Mediterranean down to 4200 m depth in October 2001. Large mesozooplankton (333 μm nets) was sieved into five size fractions, and the δ13C and δ15N values of the fractions were measured as well as the δ15N values of total small mesozooplankton (100 μm nets) and specific mesozooplankton taxa. These measurements allow insights into the source of the diet and the trophic level relative to sinking and suspended particulate organic matter. Overall, biomass and abundance of zooplankton was low, reflecting the oligotrophic character of the eastern Mediterranean. Stable nitrogen isotope values of mesozooplankton were low (1–4‰) and close to zero in suspended particles at the surface. This indicates that the fixation of atmospheric nitrogen probably contributes to the N-pool in the eastern Mediterranean. Such low values were also found in sinking particles in deep waters and in most zooplankton size classes. However, suspended particles and mesozooplankton in the size class 0.5–1 mm, which was primarily composed of the deep-sea species Lucicutia longiserrata, showed higher values at depths below 1000 m. There is some indication that L. longiserrata was able to utilize the suspended particle pool in the deep eastern Mediterranean

Verteilung und Tagesperiodik des Evertebratenneuston im subtropischen Nordostatlantik während der "Atlantischen Kuppenfahrten 1967" von F.S. "Meteor"

In the subtropical NE Atlantic 337 neuston samples had been collected simultaneously in the 0-10 cm surface layer and in the adjacent 10-25 or 38-53 cm strata with a modified DAVID neuston catamaran. At a permanent station additional vertical stepwise hauls had been made down to 200 m with a Helgoland Larvae Net with a changing bucket device. Invertebrate neuston and other plankton was analysed in order to taclde the following problems: horizontal and vertical micro- and macrostratification, diurnal vertical migration, abundance, and feeding of species and their ontogenetical stages. Three ecological groups are described: 1. euneuston, living permanently in the uppermost layer (0-10 cm) by day and night; 2. facultative neuston, migrating into the surface layer mainly at crepuscular time and at night, or during certain phases of its early life history; 3. pseudoneuston, inhabiting with its highest concentration deeper layers, and reaching the immediate surface by relatively few specimens. - Contrary to the Black and Caspian Seas, the surface layer of the subtropical NE Atlantic is poor in nutrition compared with deeper layers. In the surface layer the total amount of invertebrates was only half of that in the adjacent strata of 10-25 and 38-53 cm, whereas the average concentration of Zooplankton in the 0-30 m macrolayer was eight times higher than in the surface layer. During daytime, particularly at noon, the average number of the invertebrate neuston diminished to 25 specimens/100 m3, and macrophages, i.e. mainly carnivores, represented about 75% of all the specimens, giving evidence of extreme scarcity of food at the sea surface. - The existence of a neuston biocoenoses in the subtropical NE Atlantic is discussed. The increase of the total number of invertebrates in the surface layer during dim light and at night, caused by facultative and pseudoneuston species, has to be regarded as an exchange of food between two communities: the biocoenoses of euneuston und pleuston on one hand and that faunal association on the other hand which is living in other habitats than at the very surface. Because of biological reasons and of terminological considerations the uppermost 5 to 10 cm thick layer at the sea surface should be called "pleustal"

Zur Ökologie der Pontellidae (Copepoda, Calanoida) im subtropischen Nordostatlantik

The zooplankton, collected in three microlayers with the use of a neuston catamaran during the cruise of R.V. "Meteor" in the subtropical Northeastern Atlantic Ocean in 1967 was studied with a view to the ecology of the calanoid copepod family Pontellidae and its position in the neuston association. The material comprises 8 species. Two of them, the abundant Pontella atlantica and Anomalocera patersoni may be used as indicator species for two different pontellid associations which were confined to special water types characterized by different ranges of surface temperatures. The biocoenotic structures in both of the species groups are to some extent - similar to those of the co-occurring communities of total invertebrate neuston. Because of this, pontellids are considered to be a useful help in studying principal changes in structures of zooplankton due to the hydrographic environment. All the pontellid species, their developmental as well as their mature stages, showed daily vertical migrations, but of different extent and distinctness. With the exception of Pontellina plumata their preference of the uppermost 10 centimeters, the "pleustal", was well-defined. Nevertheless, only Pontella atlantica can be considered an euneustonic form. There was little evidence that in the atea of investigations pontellids played a really important role in the zooneuston community; only in the oceanic part of the area, during the hours of strongest solar radiation around noon, they might perhaps gain some ecological importance as predators in the surface layer