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  • 1
    Electronic Resource
    Electronic Resource
    Determination of fine-scale vertical distribution of microbes and meiofauna in an intertidal sediment (1982)
    Springer
    Marine biology 72 (1982), S. 157-164 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A simple sampling device is described which produces thin (1 mm) sections of sediment cores. The sampler has been tested on fine sand of an intertidal sandflat and used to study the vertical distribution, over part of a tidal cycle in August, 1981, of migrating algae in the surface 20 mm of sand. Two species of Diplonies and one of Navicula showed marked changes in vertical distribution as the sandflat was flooded, but the distribution of bacteria in the sime samples did not show any change with tidal state. Spatial separation of different species of harpacticoid oppepods within the surface 20 mm of sand has also been demonstrated using this sampler, and the results suggest that different species may occupy particular fine-scale spatial niches within the sand column. The depth separation of nematode species was less well defined, except for two species with apparently the same feeding mode which were isolated from one another vertically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396916
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Production of picoplankton and small nanoplankton in the Celtic Sea (1983)
    Springer
    Marine biology 77 (1983), S. 19-27 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A significant proportion of the total primary production in the Celtic Sea (50°30′N; 07°00′W) has been found to be due to picoplankton and small nanoplankton. In July, August and October, 1982, 20 to 25% of the 14C fixed in primary production was in organisms 〉5 μm, 35 to 40% was in organisms 〈5–1 μm and 20 to 30% was in organisms〈1 μm. Bacterial production was estimated by the incorporation of 3H and would account for less than 10% of the production in the 〈1–〉0.2 μm fraction; therefore, production in the 〈1–〉0.2 μm fraction was the result of photosynthesis per se by picoplankton and could not have been due to heterotrophic bacteria utilizing exudates from larger phytoplankton. Time-course experiments demonstrated some transfer of label from the 〈1–〉0.2μm fraction to the 〉5 μm fraction, presumably by grazing, but again most of the production in this fraction was the result of photosynthesis by organisms larger than 5 μm and was not due to grazing by heterotrophic microflagellates on smaller phytoplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393206
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The size distribution of organisms in the Celtic Sea: from bacteria to Metazoa (1987)
    Springer
    Oecologia 73 (1987), S. 185-191 
    Details
    ISSN: 1432-1939
    Keywords: Pelagic ; Benthic ; Sice spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The main features of the size distribution of pelagic and benthic organisms are described, with particular reference to comprehensive studies at a single station, CS2, in the Celtic Sea. These are: 1. A more or less even distribution of biomass in all size classes of pelagic autotrophs. 2. Five size groups of pelagic heterotrophs separated from each other by roughly 103 differences in individual weight, with three well-defined gaps in the size spectrum between the four smallest size modes. 3. Benthic organisms with three size modes, the microbial peak between the two smallest pelagic modes, the meiofaunal peak between the size of pelagic ciliates and herbivorous macrozooplankton, and the macrobenthic peak at about the same size as the carnivorous macrozooplankton. Differences in the positions of the microbial peaks are thought to be associated with the different nutritional environments of free-living and surface-attached bacteria. Other features of the pelagic heterotroph spectrum are explicable in terms of the known limits to size ratios between prey and predator for suspension feeders. These limits do not apply to the benthos, the size distribution of which is largely determined by physical constraints of the sedimentary environment and the optimisation of size-related life history characteristics. Thus, constraints on body size are entirely different in the two systems, and we see little evidence for coupling between the pelagos and benthos which might result in complementary patterns of size distribution, except perhaps for interactions between the pelagic larvae of macrobenthos and the permanent macrozooplankton at the upper end of the size spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377506
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Benthic nutrient flux in a shallow coastal environment (1983)
    Springer
    Oecologia 60 (1983), S. 306-312 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ammonia and nitrate efflux from a fine sand in Carmarthen Bay was studied by incubating undisturbed cores of sediment on board ship. At the end of each incubation, the macrofaunal and bacterial biomass in each core and the organic content of the sediment were determined. Oxygen consumption was measured in another series of cores. The relationship between ammonia flux and biomass was investigated using a lattice of hypotheses approach to multiple linear regression, where all possible submodels of a general model are fitted. Ammonia flux was significantly related to the biomass of polychaetes and molluscs and “other macrofauna” but the inclusion of bacterial biomass did not improve the regressions. The estimated annual efflux of ammonia was 778 mmol N m-2 which is 44% of the estimated annual nitrogen demand of the phytoplankton. However, at the time of maximum primary production in June, only 16% of the phytoplankton requirement for nitrogen was met by benthic ammonia flux. Nitrate efflux was an order of magnitude less than that of ammonia and reached a maximum in the autumn. No significant relationship was found between oxygen consumption and macrofaunal or bacterial biomass at any time of the year.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376843
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Physiological ecology of picoplankton in the North Sea (1989)
    Springer
    Marine biology 102 (1989), S. 275-281 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution of cyanobacteria in the surface waters of the North Sea was measured during July 1987. Numbers of cyanobacteria ranged from 2.5x106 to 1.7x108 cells 1-1. In the majority of stations, cyanobacterial numbers were highest in the near-surface water and a subsurface maximum was found at only one station. The distribution of 14C among the end-products of photosynthesis was determined for picoplankton (〈1 μm) and other phytoplankton 〉1 μm throughout the North Sea. The majority of label was found in the protein fraction of both picoplankton and 〉1 μm phytoplankton; incorporation into lipids and polysaccharides plus nucleic acids was much lower. We interpret the large incorporation into protein to be a consequence of nutrient limitation of these natural assemblages. Photosynthetic parameters of the two size fractions were also determined. Assimilation number (P m B ) and initial slope αβ were greater for the picoplankton fraction than for phytoplankton 〉1 μm but there was no evidence of significant photoinhibition of either fraction at irradiances up to 1 000 μE m-2 s-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428289
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  • 6
    Electronic Resource
    Electronic Resource
    Photosynthetic characteristics of nanoplankton and picoplankton from the surface mixed layer (1986)
    Springer
    Marine biology 92 (1986), S. 465-474 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nanoplankton and picoplankton primary production has been studied at two oceanic stations in the Porcupine Sea-bight and at one shelf station in the Celtic Sea. At both sites, low wind conditions in June and July 1985 resulted in greatly reduced vertical turbulent mixing and a secondary, temporary thermocline developed in what is usually a well-mixed surface layer; as a result, there was physical separation of the phytoplankton within two zones of the surface mixed layer. The photosynthetic characteristics of three size fractions (〉5 μm, 〈5 to 〉1 μm and 〈1 to 〉0.2 μm) of phytoplankton populations from the two zones have been measured. Phytoplankton was more abundant at the oceanic stations and chlorophyll a values were between 1.3 and 2.2 mg chlorophyll a m-3, compared with 0.3 to 0.6 mg chlorophyll a m-3 at the shelf station; at both stations, numbers of cyanobacteria were slightly higher in the lower zone of the surface mixed layer. There was no effect of the temporary thermocline on the vertical profiles of primary production and most phtosynthesis occurred in the surface 10 m. Photosynthetic parameters of the three size fractions of phytoplankton have been determined; there was considerable day-to-day variation in the measured photosynthetic parameters. Assimilation number (P m B ) of all 〉5 μm phytoplankton was lower for the deeper than for the surface populations, but there was little change in initial slope (a B ). The small oceanic nanoplankton (〈5 to 〉1 μm) showed changes similar to the 〉5 μm phytoplankton, but the same size fraction from the shelf station showed changes that were more like those shown by the picoplankton (〈1 μm) viz, little change in P m B but an increase in a B with depth. Values of a B were generally greater for the picoplankton fraction than for the larger phytoplankton, but values of adaptation parameter (I k )(=P m B /α) were not always less. There was little evidence to support the hypothesis that these populations of picoplankton were significantly more adapted to low light conditions than the larger phytoplankton cells. When photosynthetic parameters of the picoplankton were normalised to cell number (P m C /a C ) rather than chlorophyll a, P m C was comparable to other published data for picoplankton, but a C was much lower. The maximum doubling time of the picoplankton at saturating irradiance is calculated to be ca. 8.5 h for the oceanic population and ca. 6.2 h for the shelf population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392506
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  • 7
    Electronic Resource
    Electronic Resource
    Demands of the herbivore community on phytoplankton production in the Celtic Sea in August (1985)
    Springer
    Marine biology 87 (1985), S. 297-306 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zooplankton species diversity in the Celtic Sea in August 1982 was low; two species of copepod and two species of euphausiid accounted for 90 to 95% of the biomass sampled by a 280 μm-mesh net. Some 75% of the primary production was by phytoplankton smaller than 5 μm. The demands of both the macrozooplankton and the microzooplankton have been examined. If it is assumed that macrozooplankton cannot efficiently graze particles smaller than 5 μm, there was insufficient primary production to meet the demands of the copepods and euphausiids; however, there would have been sufficient if these animals could graze phytoplankton 5 to 1 μm. Ciliates were in competition with the macrozooplankton for phytoplankton and could not have been significant grazers of bacterial biomass. The majority of microflagellates were autotrophic; less than 10% of the population did not possess a chloroplast and were presumably heterotrophs. Bacterial production was low and was insufficient to meet the demands of the heterotrophic microflagellates, but there was sufficient production by the picophytoplankton to meet microflagellate requirements. The data do not appear to support the ideas of a significant flow of energy through the “microbial loop” in the Celtic Sea in August.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397809
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  • 8
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    Pelagic Ecosystems in a High CO2 Ocean: the Mesocosm Approach (2004)
    In:  EPIC3Solas Open Science Conference 2004, 13.-16.October, Halifax, Nova Scotia, Canada.
    Details
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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    PAPER (OA)
  • 9
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    Pelagic Ecosystems in a High CO2 Ocean: the Mesocosm Approach (2004)
    In:  [Poster] In: SOLAS Open Science Conference 2004, 13.-16.10.2004, Halifax, Canada .
    Details
    Publication Date: 2012-07-06
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: slideshow
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    OceanRep: Poster
  • 10
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    Supply and demand of nutrients and dissolved organic matter at and across the NW European shelf break in relation to hydrography and biogeochemical activity (2001)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 48 (14-15) . pp. 3023-3047.
    Details
    Publication Date: 2020-08-05
    Description: As part of the OMEX I project, nutrient determinations were made on 17 cruises in the region of the Goban Spur and La Chapelle Bank between 46 and 51°N, in all seasons of the year, between 1993–1995. Over this period no change was detectable in the structure of the water masses below the deep winter mixed layer. The N : P (dissolved nitrate-to-phosphate) ratio changed from 16 at 100-m depth to less than 15 at 3300-m depth. At intermediate depths nutrient and oxygen data indicate the presence of Mediterranean Outflow water overlying Labrador Sea Water at its most eastern extension. Estimated maximum levels of production in the spring bloom are the total N-limited new primary production equivalent between 24 and 41 gC m−2, the equivalent maximum diatom production is 11 gC m−2. Measurements during the spring bloom suggest a conversion factor of 1 μM nitrate to 1 μg l−1 chlorophyll, at the shelf break, which is consistent with other recent measurements in European shelf seawaters. Sediment trap data suggest that 80% (5.4 g m−2) of the opal produced in the spring bloom dissolved before reaching the sediment trap at 600 m. A comparison of the winter and summer profiles for dissolved silicon suggests a similar dissolution of 9±3 g opal m−2 above 300-m depth. Measurements of dissolved organic carbon (DOC) in September 1994 show an enrichment of 7 μM-C above the seasonal thermocline relative to the winter values (52±4 μM). In winter dissolved organic nitrogen represents 40% of the pool of total dissolved nitrogen. There is no consistent evidence of an increase in the concentration of DON during summer. Measurements of nitrate in surface waters in January 1994 show that concentrations off-shelf vary with the temperature of the water and are related to the depth of winter mixing. Mixing in surface waters is discontinuous at the shelf break, demonstrating the degree to which exchange across the shelf break is limited even in winter. OMEX winter measurements of nitrate concentrations can be used to estimate the flow of water across the shelf break that would be required to maintain the nitrogen balance in the North Sea at a steady state. The estimate is 0.6 Sv (1 Sv=106 m3 s−1), which is similar to an earlier estimate of a total flow of 1.7 Sv based on salt budgets (cf. Huthnance, Deutsche Hydrographische Zeitschrift, 49 (1997) 153).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0967-0645(01)00031-5
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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