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  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Diatoms are the major contributors to phytoplankton blooms in lakes and in the sea and hence are central in aquatic ecosystems and the global carbon cycle. All free-living diatoms differ from other phytoplankton groups in having silicified cell walls in the form of two ‘shells’ (the ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The growth cycle in nutrient-rich, aquatic environments starts with a diatom bloom that ends in mass sinking of ungrazed cells and phytodetritus. The low grazing pressure on these blooms has been attributed to the inability of overwintering copepod populations to track them temporally. We ...
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  • 3
    Publication Date: 2022-05-18
    Description: Nutrient and oxygen levels and ratios, primary production and data on bacterial activity recorded during an enclosure experiment carried out in July/August 1974 in Kiel Bight are presented and discussed. Considerable amounts of nutrients were released from the sediments due to density displacement of interstitial water and this was found to have a direct effect on phytoplankton production. Ammonia levels outside the enclosure were low and, in contrast to other nutrients and oxygen which were highly correlated with each other, ammonia showed no correlation with any other parameter. Presumably, ammonia released from the sediments escaped detection due to rapid uptake by phytoplankton. Reactive nitrogen, specifically ammonia thus seemed to be the limiting factor for primary production during the experiment. Sediment flushing also led to increased bacterial numbers and activity in the water column, however, this effect could only be measured inside the enclosure. These aspects of sediment/water interaction and their effect on the dynamics of shallow coastal ecosystems are discussed.
    Type: Article , NonPeerReviewed
    Format: text
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  • 4
    Publication Date: 2022-05-23
    Description: Results obtained from short-term (8 h to 24 h intervals) measurements of physical, chemical and biological properties of the 70 m water column from an anchor station in the Bornholm Sea over a 10-day period are presented and discussed. Phytoplankton biomass concentration and production rates indicated that the spring bloom was in progress in this period. The onset of the spring bloom occurred prior to the advent of thermal stratification. Peak growth rates, accompanied by nutrient depletion and biomass accumulation in surface layers, were concomitant with calm weather and a cloudless sky after which a part of the population was observed to sink out of the water column unimpeded by the permanent halocline. Maximum sinking rates of the dominant species, Skeletonema costatum, ranged between 30 to 50 m per day during this event. The development of the spring bloom apparently takes place in a series of events during which periods of low production alternate with periods of high production and rapid sedimentation of parts of the population.
    Type: Article , NonPeerReviewed
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  • 5
    Publication Date: 2022-05-03
    Description: 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.
    Type: Article , NonPeerReviewed
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