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  • 1
    Electronic Resource
    Electronic Resource
    On the cost of vertical migration: are feeding conditions really worse at greater depths? (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. The ultimate explanation for diel vertical migration (DVM) of zooplankton is the avoidance of visual predation in surface waters. Studies on migrating zooplankton have shown that remaining in the cold and food-poor hypolimnion during the day, however, has demographic costs. Higher temperatures and greater food concentrations in the surface waters are thought to be the main reasons why Daphnia species move upwards at night.2. In this study, we investigated the growth condition of daphniids raised on seston taken from different depths from a lake with and without a deep-water chlorophyll maximum.3. Juvenile growth rates of Daphnia galeata x hyalina from the lake without a deep-water chlorophyll maximum were similar for all treatments. After temperature correction, however, growth rates were significantly higher on seston taken from the surface layers.4. In contrast, in the lake with the deep-water chlorophyll maximum, D. galeata growth rates were higher in deeper strata, even after temperature correction. Although this lake had a weak temperature gradient, D. galeata left the food-rich strata at night and migrated into the surface food-poor environment. Invertebrate predation and oxygen depletion are probably not the reasons for the nocturnal upward migration into the surface strata. Therefore, we assume that D. galeata migrates upwards to take advantage of higher temperatures. Using several temperature–egg-development models, we could not, however, fully explain this behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.00995.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Weeds resistant to chlorsulfuron and atrazine from the north-east grain region of Australia (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 37 (1997), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The resistance of weeds to triazine and sulfonylurea herbicides has been recorded in several countries. The extent of the problem in the north-east grain region of Australia is uncertain. In an initial study, resistance to chlorsulfuron and atrazine in 15 weed species was investigated. The study showed that at least six of them have evolved resistance to one or other of these herbicides. Two collections of Rapistvum rugosum L., three of Sisymbrium orientale L., five of Sonchus oleraceus L., one of Fallopia convolvulus (L.) A. Love and one of Sisymbrium rhellungii O. Schultz were resistant to the recommended rate of chlorsulfuron (15 g a.i. ha-1). Resistance to chlorsulfuron was not discovered in three collections of Sisymbrium L., two of Brassica tournefortii Gouan. three of Emex australis Steinh. and 11 of Phalaris paradoxa L. Two collections of Urochtoa panicoides Beauv. were resistant, and three collections possibly resistant, to the recommended rate of atrazine(1.8 kg a.i. ha-1). Resistance to atrazine was not found in 12 collections of Hibiscus urionum L., nine of Salvia reflexa L., two of Parthenium hysterophorus L., two of Amaranthus viridis L. and 14 of Echinochloa colona (L) Link. The resistance status of four weeds (R. rugosum. F. convolvulus, S. thellungii and U. panicoides was confirmed using a multiple dose-response screen and is the first report of resistance for these species. Herbicide usage records show that resistance has developed after 3-10 years of selection with chlorsulfuron and 2-15 years of selection with atrazine, with no correlation between the frequency of use and the degree of resistance for any of the species where eight or more collections were made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3180.1997.d01-56.x
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  • 3
    Electronic Resource
    Electronic Resource
    Long-term dynamics of small-bodied and large-bodied cladocerans during the eutrophication of a shallow reservoir, with special attention for Chydorus sphaericus (1997)
    Springer
    Hydrobiologia 360 (1997), S. 233-242 
    Details
    ISSN: 1573-5117
    Keywords: Chydorus ; body size ; zooplanktoncommunity ; eutrophication ; detrital food web ; Cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eutrophication in Tjeukemeer involved a gradualincrease in chlorophyll concentrations from ca. 30 mg m-3in 1968–69 to 125 mg m-3 in 1976.From 1976 onwards, chlorophyll concentrations remainedat a high level fluctuating between100–225 mg m-3. Hillbricht-Illkowska (1977)hypothesized that small-bodied species will becomeincreasingly abundant and dominant over large-bodiedspecies with increasing eutrophication. We tested thishypothesis using observations from life historyexperiments on Chydorus sphaericus, combinedwith data from 25 years of field observations on thepopulation dynamics of cladocerans in Tjeukemeer.In life history experiments with C. sphaericus,the fitness measure r in treatments with naturallake seston and laboratory cultured green algae wassignificantly higher on lake seston from Tjeukemeer,containing a high proportion of detritus. Thissuggests that detrital particles are good quality foodfor C. sphaericus. Field observations during theperiod 1968–1976 showed that all three categories ofcladocerans: C. sphaericus,'other' small-bodiedcladocerans (predominantly Bosmina spp.) andlarge-bodied cladocerans (predominantly Daphniagaleata), increased in biomass with increasingchlorophyll concentration. However, of these threecladoceran categories only sphaericus showeda distinct and significant increase whereas the othertwo only showed a marginally significant increase.During the period 1977–1992, both 'other' small-bodiedcladocerans and C. sphaericus significantlydecreased in biomass with increasing chlorophyllconcentration, whereas the biomass of the large-bodiedcladocerans significantly increased with increasingchlorophyll content. These observations are not inagreement with the hypothesis that small-bodiedzooplankton become increasingly abundant withincreasing eutrophication. We suggest that theobserved trends are partially caused by a food effect,and partially caused by predation pressure. Daphnia shows a better response to the increase indetritus and filaments of Cyanobacteria thansmall-bodied cladocerans, but is more vulnerable tofish predation. Densities of 0+ zooplanktivorous fishshow strong annual fluctuations in Tjeukemeer, andbecause of hydrological conditions, 0+ fish abundancein this lake is probably negatively related tochlorophyll content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003148600983
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  • 4
    Electronic Resource
    Electronic Resource
    Book reviews (1974)
    Springer
    Plant ecology 29 (1974), S. 149-153 
    Details
    ISSN: 1573-5052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02389721
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  • 5
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    Plankton responses to ocean acidification: The role of nutrient limitation (2018)
    Elsevier
    In:  Progress in Oceanography, 165 . pp. 11-18.
    Details
    Publication Date: 2021-02-08
    Description: Highlights: • Ocean acidification increases phytoplankton standing stock. • This increase is more pronounced in smaller-sized taxa. • Primary consumers reac differently depending on nutrient availability. • Bacteria and micro-heterotrophs benefited under limiting conditions. • In general, heterotrophs are negatively affected at nutrient replete periods. Abstract: In situ mesocosm experiments on the effect of ocean acidification (OA) are an important tool for investigating potential OA-induced changes in natural plankton communities. In this study we combined results from various in-situ mesocosm studies in two different ocean regions (Arctic and temperate waters) to reveal general patterns of plankton community shifts in response to OA and how these changes are modulated by inorganic nutrient availability. Overall, simulated OA caused an increase in phytoplankton standing stock, which was more pronounced in smaller-sized taxa. This effect on primary producers was channelled differently into heterotroph primary consumers depending on the inorganic nutrient availability. Under limiting conditions, bacteria and micro-heterotrophs benefited with inconsistent responses of larger heterotrophs. During nutrient replete periods, heterotrophs were in general negatively affected, although there was an increase of some mesozooplankton developmental stages (i.e. copepodites). We hypothesize that changes in phytoplankton size distribution and community composition could be responsible for these food web responses.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.pocean.2018.04.006
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Daphnia versus copepod impact on summer phytoplankton: functional compensation at both trophic levels (2003)
    Springer
    In:  Oecologia (135). pp. 639-647.
    Details
    Publication Date: 2019-09-23
    Description: Here we report on a mesocom study performed to compare the top-down impact of microphagous and macrophagous zooplankton on phytoplankton. We exposed a species-rich, summer phytoplankton assemblage from the mesotrophic Lake Schöhsee (Germany) to logarithmically scaled abundance gradients of the microphagous cladoceran Daphnia hyalina×galeata and of a macrophagous copepod assemblage. Total phytoplankton biomass, chlorophyll a and primary production showed only a weak or even insignificant response to zooplankton density in both gradients. In contrast to the weak responses of bulk parameters, both zooplankton groups exerted a strong and contrasting influence on the phytoplankton species composition. The copepods suppressed large phytoplankton, while nanoplanktonic algae increased with increasing copepod density. Daphnia suppressed small algae, while larger species compensated in terms of biomass for the losses. Autotrophic picoplankton declined with zooplankton density in both gradients. Gelatinous, colonial algae were fostered by both zooplankton functional groups, while medium-sized (ca. 3,000 µm3), non-gelatinous algae were suppressed by both. The impact of a functionally mixed zooplankton assemblage became evident when Daphnia began to invade and grow in copepod mesocosms after ca. 10 days. Contrary to the impact of a single functional group, the combined impact of both zooplankton groups led to a substantial decline in total phytoplankton biomass.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00442-003-1214-7
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    The first ocurrence of the ctenophore Mnemiopsis leidyi in the North Sea (2007)
    Springer
    In:  Helgoland Marine Research, 61 (2). pp. 153-155.
    Details
    Publication Date: 2018-05-28
    Description: After the discovery of large densities of Mnemiopsis leidyi in the Baltic Sea near Kiel by Javidpour et al. (First record of Mnemiopsis leidyi A. Agassiz 1865 in the Baltic Sea, 2006) in October 2006, we investigated the gelatinous zooplankton in the North Sea near Helgoland and recorded Mnemiopsis leidyi for the first time in the North Sea, albeit in much lower densities than those recorded in the Baltic Sea.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s10152-006-0055-2
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Effects of high CO2 and warming on a Baltic Sea microzooplankton community (2016)
    Oxford University Press
    Details
    Publication Date: 2016-02-27
    Description: Global warming and ocean acidification are among the most important stressors for aquatic ecosystems in the future. To investigate their direct and indirect effects on a near-natural plankton community, a multiple-stressor approach is needed. Hence, we set up mesocosms in a full-factorial design to study the effects of both warming and high CO 2 on a Baltic Sea autumn plankton community, concentrating on the impacts on microzooplankton (MZP). MZP abundance, biomass, and species composition were analysed over the course of the experiment. We observed that warming led to a reduced time-lag between the phytoplankton bloom and an MZP biomass maximum. MZP showed a significantly higher growth rate and an earlier biomass peak in the warm treatments while the biomass maximum was not affected. Increased p CO 2 did not result in any significant effects on MZP biomass, growth rate, or species composition irrespective of the temperature, nor did we observe any significant interactions between CO 2 and temperature. We attribute this to the high tolerance of this estuarine plankton community to fluctuations in p CO 2 , often resulting in CO 2 concentrations higher than the predicted end-of-century concentration for open oceans. In contrast, warming can be expected to directly affect MZP and strengthen its coupling with phytoplankton by enhancing its grazing pressure.
    Print ISSN: 1054-3139
    Electronic ISSN: 1095-9289
    Topics: Biology , Geosciences , Physics
    Published by Oxford University Press
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    PAPER CURRENT
  • 9
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    Plankton responses to ocean acidification: The role of nutrient limitation (2018)
    In:  EPIC3Progress in Oceanography, 165, pp. 11-18, ISSN: 00796611
    Details
    Publication Date: 2019-08-19
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 10
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    Major shift in the copepod functional community of the southern North Sea and potential environmental drivers (2023)
    Oxford University Press (OUP)
    In:  EPIC3ICES Journal of Marine Science, Oxford University Press (OUP), pp. fsad160-fsad160, ISSN: 1054-3139
    Details
    Publication Date: 2023-11-23
    Description: 〈jats:title〉Abstract〈/jats:title〉 〈jats:p〉Copepods form the bulk of secondary production in marine ecosystems and are a major resource for higher trophic levels. Copepods are highly sensitive to environmental changes as they are ectotherms with a short life span whose metabolism and development depend on abiotic conditions. In turn, changes in their functional structure (i.e. functional trait composition) can have impacts on ecosystems. We examined changes in the copepod functional community in the North Sea over the past five decades, using a trait-based approach. We observed a shift around 1986–1988: the copepod community was initially dominated by larger herbivores, with a long development time, diapause ability, and highest abundances in summer. This community changed abruptly after 1986–1988, to a dominance of smaller carnivore taxa, with shorter development times, less ability to enter diapause, and that display higher abundances in autumn. This rapid reorganization could be driven by higher water temperatures, lower dinoflagellate abundances, and lower nutrient concentrations. These changes could impact adjacent trophic levels, such as phytoplankton on which several species graze or fish larvae, leading to a mismatch situation with consequences for fish recruitment. Our results emphasize the impact that global and regional changes could have on coastal ecosystems through the role played by copepods.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
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