The Annual Cycle of Kiel Bight Plankton: A Long-Term Analysis

Over the past decade, the annual cycle of the major pelagic processes in relation to environmental factors and species composition of the plankton has been studied intensively at a fixed station in Kiel Bight. A series of sequential phases, differentiated according to characteristic properties, succeed each other in a recurring pattern each year. The following phases have been differentiated: the spring diatom bloom, the late spring copepod maximum, the summer stratification, the fall blooms and the winter dormancy. Each phase represents a particular pattern of biogenous element cycling, both within the pelagic system and between the pelagic and benthic systems. Each phase is also characterized by a spectrum of dominant species, many of which do not recur each year. Greatest variation is found amongst bloom diatoms, whereas large, slow-growing species such as the Ceratia and most metazooplankton are highly recurrent. Variation in species composition is not related to long-term trends since the past century, in spite of the considerable increase in anthropogenic nutrient input to the Bight. Short-term events appear to determine occurrence of fast-growing species, many of which have benthic resting stages in their life histories. It is concluded that more attention should be paid to life history strategies of species if the mechanisms of seasonal succession are to be elucidated. Long-term observations on appearance or absence of the various species in relation to environmental properties can provide clues as to the nature of these life history strategies

Zur Leistungsfähigkeit der bei produktionsbiologischen Untersuchungen verwendeten Filtersorten

Die Leistungsfähigkeit -zusammengesetzt aus Retention, Durchlaufgeschwindigkeit und Variabilität-verschiedener in der marinen Produktionsbiologie verwendeter Filtersorten wurde mit Hilfe der Chlorophyll-a Bestimmung untersucht. Jeweils zwei der zehn getesteten Filtersorten wurden mit dem t-Test (nach STUDENT) statistisch ausgewertet. Außer bei den vier untersuchten Glasfaserfiltern konnten keine bedeutenden Unterschiede in der Retention der untersuchten Filter festgestellt werden. Dies stimmt nicht überein mit den Ergebnissen anderer Autoren, die die 14C-Methode zur Bestimmung der Retention von photosynthetisierendem Phytoplankton durch Filter verschiedener Porengröße verwendeten. Eine Erklärung für diese Diskrepanz ist, daß viele Flagellaten durch die Filtration beschädigt werden. Das Zellplasma und die kleineren Organellen gehen dadurch verloren, die relativ großen und festen Chloroplasten werden jedoch von den meisten Filtern vollständig zurückgehalten. Filter efficiency, consisting of retention, variability and filtration time of different filters used in biological oceanography was tested with the help of the chlorophyll-a method. Of the ten filters tested, two were compared with one another in each case. The chlorophyll-a content of the filters after filtration was used as an index for their retention. The results obtained were statistically evaluated with the Student's t-test. With the exception of the four fibreglass-filters tested, no significant difference in the retention of the filters was found. This does not tally with the results of other authors who used the 14C method to determine the retention of photosynthesizing phytoplankton by filters of varying poresize. This discrepancy could be explained by the fact that many flagellates that are damaged in the course of filtration, lose their plasma and the smaller organelles; the large and firm chloroplasts however, are retained by most filters