Gerhard Drebes

Thalassiosira species (Bacillariophyceae, Thalassiosirales) in the North Sea at Helgoland (German Bight) and Sylt (North Frisian Wadden Sea) – a first approach to assessing diversity

Thalassiosira species are an important component of phytoplankton populations in pelagic waters around the islands of Helgoland and Sylt in the German North Sea. This taxonomic study revealed the presence of at least 27 species, 21 at Helgoland and 21 at Sylt. Fifteen species had not been recorded previously for Helgoland (T. aestivalis, T. angulata, T. concaviuscula, T. curviseriata, T. delicatula, T. diporocyclus, T. hendeyi, T. kuschirensis, T. minima, T. minuscula, T. oceanica, T. pacifica, T. proschkinae, T. tealata, T. tenera) and 16 for Sylt (T. aestivalis, T. angulata, T. concaviuscula, T. constricta, T. curviseriata, T. delicatula, T. guillardii, T. hendeyi, T. lundiana, T. mediterranea, T. minima, T. pacifica, T. partheneia, T. punctigera, T. tealata, T. tenera). We provide brief descriptions with illustrations and document the seasonal occurrence of these species at the two stations. We also discuss investigation methods used for different levels of species recognition, namely Utermöhl counts, light microscopical observations of living net-samples as well as scanning electron microscopy of net-samples and isolated cultures. Clonal cultures of some species were established to facilitate the taxonomic investigations and 18S ribosomal DNA sequencing was carried out to complement the morphological studies. A perspective for a routine species-level assessment strategy is given.

Dissodinium pseudolunula (Dinophyta), a parasite on copepod eggs

Direct observation as well as culture experiments revealed Dissodinium pseudolunula as an ectoparasite on eggs of the marine planktonic copepod Temora longicornis. The vegetative life cycle, especially the parasitic phase, which involves phagocytosis, is reported for the first time. The species resembles D. pseudocalani, which is also parasitic upon copepod eggs. The taxonomic position and the survival of D. pseudolunula during the absence of the host in the winter is discussed.

Possible resting spores of Dissodinium pseudolunula (Dinophyta) and their relation to other taxa

Previously unknown dinoflagellate resting spores found in the North Sea were germinated in culture. The emerging dinospores proved to be identical with those of an ectoparasite, Dissodinium pseudolunula. Hence, the resting spores are interpreted as an integral stage in the life cycle of this species. It is shown that Pyrocystis margalefii from the Mediterranean Sea is probably identical with the resting stages of D. pseudolunula. Possible affinity to the fossil Palaeocystodinium golzowense is discussed.

Semi-quantitive microplankton analysis (Sylt Roads Time Series) in the Wadden Sea off List, Sylt, North Sea in 1987

See data in other version: 1987 - https://doi.pangaea.de/10.1594/PANGAEA.861296 / 1988 - https://doi.pangaea.de/10.1594/PANGAEA.861297 / 1989 - https://doi.pangaea.de/10.1594/PANGAEA.861298 / 1990 - https://doi.pangaea.de/10.1594/PANGAEA.861299 / 1991 - https://doi.pangaea.de/10.1594/PANGAEA.861300 / 1992 - https://doi.pangaea.de/10.1594/PANGAEA.861301 / 1993 - https://doi.pangaea.de/10.1594/PANGAEA.861302 / 1994 - https://doi.pangaea.de/10.1594/PANGAEA.861303 / 1995 - https://doi.pangaea.de/10.1594/PANGAEA.861304 / 1996 - https://doi.pangaea.de/10.1594/PANGAEA.861305 / 1997 - https://doi.pangaea.de/10.1594/PANGAEA.861306 / 1998 - https://doi.pangaea.de/10.1594/PANGAEA.861307 / 1999 - https://doi.pangaea.de/10.1594/PANGAEA.861308 / 2000 - https://doi.pangaea.de/10.1594/PANGAEA.861309 / 2001 - https://doi.pangaea.de/10.1594/PANGAEA.861310