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  • 1
    Electronic Resource
    Electronic Resource
    Blaue Liste Institute (1999)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 29 (1999), S. 375-375 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.960290612
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Demonstration of β-N-acetyl-D-glucosaminidase and β-N-acetyl-D-hexosaminidase in Drosophila Kc-cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 17 (1991), S. 3-13 
    Details
    ISSN: 0739-4462
    Keywords: intra- and extracellular enzymes ; kinetic properties ; inhibition ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Kc-cells from Drosophila melanogaster, grown under serum-free conditions, produce two β-hexosaminidases and secrete these enzymes into the medium. The two enzymes were separated by DEAE-exchange chromatography. According to their substrate specificities one enzyme is a β-N-acetyl-D-glucosaminidase (E.C.3.2.1.30), the other one a β-N-acetyl-D-hexosaminidase (E.C.3.2.1.52). The β-N-acetyl-D-glucosaminidase is predominant in the medium, the β-N-acetyl-D-hexosaminidase within the cells. The Km values for the substrates pNP-GlcNAc, pNP-GalNAc, and (GlcNAc)2 are 0.8, 16.73, and 1.67 mM for the β-N-acetyl-D-glucosaminidase and 0.24, 0.44, and 0.2 mM for the β-N-acetyl-D-hexosaminidase. Both enzymes are inhibited by the products and the β-N-acetyl-D-glucosaminidase is also inhibited stereospecifically by the substrates pNP-GlcNAc and (GlcNAc)2. Both enzymes are inhibited in a partial competitive way by acetamidolactones, the Kis being as low as 0.1 μM.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940170103
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Physical properties of β-N-acetyl-D-glucosaminidase and β-N-acetyl-D-hexosaminidase from Drosophila Kc-cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Archives of Insect Biochemistry and Physiology 18 (1991), S. 45-53 
    Details
    ISSN: 0739-4462
    Keywords: molecular mass ; pH and temperature optima ; thermal stability ; influence of ionic strength ; Chemistry ; Food Science, Agricultural, Medicinal and Pharmaceutical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Kc-cells from Drosophila produce two different β-D-hexosaminidases, a β-N-acetyl-D-glucosaminidase (E.C.3.2.1.30) and a β-N-acetyl-D-hexosaminidase (E.C.3.2.1.52), which are also secreted into the medium. The Mr of both enzymes is about 126,000 ± 9,700; the S-values are 8.37 ± 0.44. Both enzymes have about the same pH optima at 5.5 and the same thermal stability. The temperature optima are identical (50°C) for both enzymes if p-nitrophenyl-N-acetylglucosaminide is used as a substrate. However, when p-nitrophenyl-N-acetylgalactoseaminide is used as the substrate the β-N-acetyl-D-hexosaminidase has a temperature optimum about 10°C higher. With higher salt concentrations, the activity of the β-N-acetyl-D-glucosaminidase increases, whereas β-N-acetyl-D-hexosaminidase is inhibited. Both enzymes also differ in their sensitivity to urea, the β-N-acetyl-D-hexosaminidase being less sensitive than the β-N-acetyl-D-glucosaminidase.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/arch.940180105
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  • 4
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    Baltic Sea diazotrophic cyanobacterium is negatively affected by acidification and warming (2018)
    Inter Research
    In:  Marine Ecology Progress Series, 598 . pp. 49-60.
    Details
    Publication Date: 2021-02-08
    Description: Nitrogen fixation is a key source of nitrogen in the Baltic Sea which counteracts nitrogen loss processes in the deep anoxic basins. Laboratory and field studies have indicated that single-strain nitrogen-fixing (diazotrophic) cyanobacteria from the Baltic Sea are sensitive to ocean acidification and warming, two drivers of marked future change in the marine environment. Here, we enclosed a natural plankton community in twelve indoor mesocosms (volume ~1400 L) and manipulated pCO2 to yield six CO2 treatments with two different temperature treatments (16.6°C and 22.4°C, pCO2 range = 360 – 2030 μatm). We followed the filamentous, heterocystous diazotrophic cyanobacteria community (Nostocales, primarily Nodularia spumigena) over four weeks. Our results indicate that heterocystous diazotrophic cyanobacteria may become less competitive in natural plankton communities under ocean acidification. Elevated CO2 had a negative impact on Nodularia sp. biomass, which was exacerbated by warming. Our results imply that Nodularia sp. may contribute less to new nitrogen inputs in the Baltic Sea in future.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps12632
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  • 5
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    Simultaneous analysis of δ13C, δ15N and δ34S ratios uncovers food web relationships and the trophic importance of epiphytes in an eelgrass, Zostera marina community (2014)
    Inter Research
    In:  Marine Ecology Progress Series, 497 . pp. 93-103.
    Details
    Publication Date: 2019-02-06
    Description: Simultaneous analysis of carbon, nitrogen and sulphur stable isotope ratios was applied in this pilot study to examine the food web of a Zostera marina L. system in the western Baltic Sea. Samples of three potential food sources: eelgrass, epiphytic algae and seston, as well as 69 consumer species were collected during the growing season of Z. marina from March to September 2011. The measured δ13C values of epiphytes (-14.1‰ ± 1.8 SD) were close to δ13C values of eelgrass (-11.6‰ ± 1.8 SD), impeding a clear distinction of those two carbon sources, whereas seston δ13C values (-20.9‰ ± 3.5 SD) were clearly different. This frequently encountered problem was solved by the additional use of δ34S, which resulted in easily distinguishable values for sediment and seawater derived sulphur. Values of primary producer δ34S ranged from 5.6‰ (± 2.3 SD) for Z. marina leaves to 14.2‰ (± 1.6 SD) for epiphytes and 11.9‰ (± 3.3 SD) for seston. The combination of δ34S and δ13C values made a separation of carbon sources possible and enabled the allocation of potential food sources to consumers and a description of their trophic relationships. The data of stable isotope ratio analysis of this eelgrass community strongly indicate a food web based on epiphyte and seston production. δ15N values show a food web consisting of large numbers of generalists and a high degree of omnivory amongst the consumer species analysed. This implies an occupation of every trophic position possible, which is supported by a continuous distribution of δ15N values. Previously described eelgrass food webs may have to be re-evaluated to include sulfur in order to provide a clear picture on primary carbon sources.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3354/meps10569
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Effect of algal species and concentration on development and fatty acid composition of two harpacticoid copepods,Tisbesp. andTachidius discipes, and a discussion about their suitability for marine fish larvae (2014)
    Wiley-Blackwell
    In:  Aquaculture Nutrition, 20 (1). pp. 44-59.
    Details
    Publication Date: 2019-09-23
    Description: We compared the development and fatty acid content of the harpacticoid copepods Tachidius discipes and Tisbe sp. fed with different microalgal species (Dunaliella tertiolecta, Rhodomonas sp., Phaeodactylum tricornutum, Isochrysis galbana and a concentrate of Pavlova sp.), which differed in cell size and fatty acid composition. Tisbe could develop in 11 days with every alga to the same average stage, whereas Tachidius developed poorly when fed with Isochrysis and Dunaliella. Feeding with Phaeodactylum resulted in a fast development of both copepods at low algal concentrations. However, reproduction was higher with Rhodomonas as food than with the other algae. Fatty acid compositions of copepods were influenced by their food source, but both were able to convert docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from precursors. Tachidius fed with Rhodomonas or Phaeodactylum was closest to the DHA/EPA/arachidonic acid (ARA) ratio of 10 : 5 : 1 considered optimal for some marine fish larvae. Tachidius showed similar development and reproduction capacity as Tisbe, but requested higher absolute fatty acid contents in the diet. Tisbe was superior in the utilization of bacteria as additional food source and the bioconversion of precursor fatty acids. Phaeodactylum and Rhodomonas are recommendable food sources for both copepod species, but Phaeodactylum is more easily cultured.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/anu.12051
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  • 7
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    Some like it hot: the protozooplankton–copepod link in a warming ocean (2015)
    Inter Research
    In:  Marine Ecology Progress Series, 519 . pp. 103-113.
    Details
    Publication Date: 2020-01-21
    Description: The combined effects of warming and overwintering copepod densities on the spring succession of Baltic Sea plankton were investigated using indoor mesocosms. Three zooplankton (1.5, 4 and 10 copepods L-1) and two temperature levels called ∆0°C and ∆6°C (0°C and 6°C above the present day temperature scenario for Kiel Bight) were chosen. Both, the timing and the duration of the protozooplankton (PZP) bloom were significantly affected by temperature, but not by copepod density. In contrast, the bloom intensity of PZP was highly affected by the factors temperature and copepod density and its interaction. This suggests that at elevated temperature conditions PZP grows faster but, at the same time, are subject to higher top-down control by copepods. At low temperatures and low copepod densities, PZP in turn fully escaped from copepod predation. Further changes in the overwintering copepod densities resulted in a strong ciliate suppression of which small-sized ciliates (〈30 µm) were especially vulnerable to copepod predation while other PZP size classes remained unaffected. In conclusion, the results presented point at a pivotal regulating role of overwintering copepods under future warming condition. Further, warming was shown to cause a distinct match between phytoplankton and PZP thus strengthening trophic pathways through PZP. Our findings are discussed in the context of the ‘trophic link-sink’ debate by considering potential alterations in the flux of matter and energy up the food web.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps11081
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  • 8
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    Community interactions dampen acidification effects in a coastal plankton system (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 486 . pp. 37-46.
    Details
    Publication Date: 2018-06-25
    Description: Changing seawater chemistry towards reduced pH as a result of increasing atmospheric carbon dioxide (CO2) is affecting oceanic organisms, particularly calcifying species. Responses of non-calcifying consumers are highly variable and mainly mediated through indirect ocean acidification effects induced by changing the biochemical content of their prey, as shown within single species and simple 2-trophic level systems. However, it can be expected that indirect CO2 impacts observed at the single species level are compensated at the ecosystem level by species richness and complex trophic interactions. A dampening of CO2-effects can be further expected for coastal communities adapted to strong natural fluctuations in pCO2, typical for productive coastal habitats. Here we show that a plankton community of the Kiel Fjord was tolerant to CO2 partial pressure (pCO2) levels projected for the end of this century (〈1400 µatm), and only subtle differences were observed at the extremely high value of 4000 µatm. We found similar phyto- and microzooplankton biomass and copepod abundance and egg production across all CO2 treatment levels. Stoichiometric phytoplankton food quality was minimally different at the highest pCO2 treatment, but was far from being potentially limiting for copepods. These results are in contrast to studies that include only a single species, which observe strong indirect CO2 effects for herbivores and suggest limitations of biological responses at the level of organism to community. Although this coastal plankton community was highly tolerant to high fluctuations in pCO2, increase in hypoxia and CO2 uptake by the ocean can aggravate acidification and may lead to pH changes outside the range presently experienced by coastal organisms.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.3354/meps10352
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  • 9
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    Grazing by mesozooplankton from Kiel Bight, Baltic Sea, on different sized algae and natural seston size fractions (2000)
    Inter Research
    In:  Marine Ecology Progress Series, 199 . pp. 43-53.
    Details
    Publication Date: 2018-05-09
    Description: Grazing experiments were conducted with natural mesozooplankton from Kiel Bight, Germany, using radioactive labelled phytoplankton cultures and seston size fractions. The results of experiments using phytoplankton cultures indicated that bivalve veligers performed highest clearance of particles within a size range of 4.7 to 6.3 µm, whereas optimum particle size for copepods was 15 µm. The results of experiments using labelled natural seston size fractions identified bivalve veligers and appendicularians as those responsible for the removal of particles within the smallest size class (〈2 µm). Seston size fractions larger than 5 µm were mainly cleared by copepods and nauplii. As particle size increased, the contribution of copepod clearance to total zooplankton clearance within size classes increased from 57% (〈5 µm size class) to more than 81% (30 to 100 µm size class). When the nauplii clearance rates were included, the total copepod clearance accounted for 90 to 97.6% of the total volume cleared of particles bigger than 10 µm. Despite low abundances of bivalve veligers and appendicularians in Kiel Bight at the time of the experiment, we calculated that approximately 10 and 8.5%, respectively, of the carbon ingested by total mesozooplankton was due to veliger and appendicularian grazing. The importance of bivalve veligers might be seen in their grazing on seston particles that escape predation by copepods and on the amount of energy that is therefore directed from the water column to the benthos when larvae settle.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps199043
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  • 10
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    Positive effects of mesograzers on epiphytes in an eelgrass system (2010)
    Inter Research
    In:  Marine Ecology Progress Series, 401 . pp. 77-85.
    Details
    Publication Date: 2018-06-19
    Description: Traditionally, consumer–prey interactions have been considered as purely negative, but herbivores may have positive effects on plants and their productivity. Grazing may enhance prey biomass-specific productivity by directly or indirectly reducing the competition for light, nutrients, and space. We studied the effect of 4 common mesograzers, the isopod Idotea baltica, the amphipod Gammarus oceanicus, and the gastropods Littorina littorea and Rissoa membranacea on epiphytes in an eelgrass Zostera marina L. system. Eelgrass was grown in laboratory mesocosms for a set of experiments manipulating mesograzer species identity, mesograzer density and nutrient concentration. We measured epiphyte biomass-specific productivity via incorporation of radioactive carbon. Herbivore effects on epiphyte photosynthetic capacity were strongly positive for R. membranacea, moderately positive for L. littorea and I. baltica and zero for G. oceanicus under low nutrient supply. Both gastropods increased the nitrogen content of epiphytes, especially the small R. membranacea, and enhanced epiphyte growth. The crustacean species did not increase epiphyte nutrient content, but I. baltica probably enhanced epiphyte productivity by removing the overstory of algal cells, and thus reducing competition for light, nutrients, and space. The positive effect of the 2 gastropod species disappeared under higher nutrient supply, implying the importance of nutrient limitation for this interaction. The positive effect of I. baltica remained at moderate grazer densities despite the higher nutrient concentrations.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3354/meps08412
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