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  • 2020-2024  (39)
  • 2020-2022  (4)
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  • 1
    Online Resource
    Online Resource
    Declining silicon to nitrogen ratios : effects on phytoplankton and plankton food webs (2021)
    Kiel : Universitätsbibliothek Kiel
    Details Availability
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (129 Seiten) , Illustrationen
    URL: https://nbn-resolving.org/urn:nbn:de:gbv:8:3-2021-00170-9
    URL: https://d-nb.info/1230407251/34
    URL: https://macau.uni-kiel.de/receive/macau_mods_00001148
    URN: urn:nbn:de:gbv:8:3-2021-00170-9
    DDC: 579.8
    Language: English
    Note: Enthält Zeitschriftenaufsätze
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  • 2
    Online Resource
    Online Resource
    Freshwater and Marine Ecology (2023)
    Cham : Springer International Publishing | Cham : Imprint: Springer
    Details Availability
    Keywords: Freshwater ecology. ; Marine ecology. ; Ecology . ; Oceanography. ; Biodiversity. ; Bioclimatology. ; Physiology.
    Description / Table of Contents: Chapter 1. Introduction -- Chapter 2. The Aquatic Habitat -- Chapter 3. Life Forms of Aquatic Organisms -- Chapter 4. Ecophysiology -- Chapter 5. Populations -- Chapter 6. Interactions -- Chapter 7. Communities and Ecosystems -- Chapter 8. Biogeochemistry -- Chapter 9. Human Impacts.
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource(XVI, 435 p. 160 illus., 112 illus. in color.)
    Edition: 1st ed. 2023.
    ISBN: 9783031424595
    URL: https://doi.org/10.1007/978-3-031-42459-5
    DOI: 10.1007/978-3-031-42459-5
    Language: English
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  • 3
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    Declining silica availability – a challenge in the North Atlantic region? (2020)
    In:  [Poster] In: EGU General Assembly 2020, 03.05.-08.05.2020, Online .
    Details
    Publication Date: 2021-01-07
    Description: Understanding how changes in limiting nutrient availability affect life in the oceans requires interdisciplinary efforts. Here we illustrate this with an example of silicon, one of the most common elements on land which bioavailable form, silicic acid (Si(OH)4), is a limiting nutrient for silicifying primary producers, such as diatoms. Silicic acid concentrations in the pelagic polar and subpolar North Atlantic have declined by 1-2 μM during spring pre-bloom conditions over the past 25 years. Many coastal areas of the North Atlantic region also face decreased relative availability of silicon due to increased riverine supply of nitrogen and phosphorus and stable or declining loads of silicon. Both declining silicic acid concentrations and declining silicon to nitrogen (Si:N) ratios limit the growth of diatoms, which are major primary producers contributing up to a quarter of global primary production. To assess the effects of declining silicon availability on phytoplankton communities we conducted a mesocosm experiment manipulating Si:N ratios and copepod grazing pressure on phytoplankton communities from the Baltic Sea. Declining Si:N ratio affected not only diatom abundance and relative biomass but also their species composition and overall plankton diversity. Our results illustrate the importance of silicon in structuring community composition at the base of temperate marine food webs. Changes in silicic acid concentrations and Si:N ratios, therefore, may have far-reaching consequences on oceanic primary production and planktonic food webs. The decline in silicon concentrations in polar and subpolar North Atlantic waters is attributed to natural multi-decadal variability but is likely amplified by reduced ocean mixing due to increased water temperatures, illustrating the need of international efforts to curb global climate change. The decline in Si:N ratios in coastal oceans also highlights the need for further reduction of nutrient pollution and improved river basin management. This may require interdisciplinary and international approaches to manage anthropogenic perturbations of the silicon cycle.
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
    DOI: 10.5194/egusphere-egu2020-4793
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    OceanRep: Poster
  • 4
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    Phytoplankton size changes and diversity loss in the southwestern Mediterranean Sea in relation to long-term hydrographic variability (2020)
    Elsevier
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    Publication Date: 2023-02-08
    Description: Structural changes in plankton primary producers have large implications for food web dynamics, energy fluxes and the vertical export of biogenic particulate carbon. Here we examine phytoplankton data spanning the period 1993–2008 from the Bay of Tunis, southwestern Mediterranean Sea, in relation to long term hydroclimate variability. We show a conspicuous shift in the structure of the phytoplankton community characterized by an increase of small-sized species and diversity loss, revealing a dominance of smaller blooming diatoms and cyanobacteria. Such changes were concurrent with marked modifications in hydroclimatic patterns experienced in the Bay of Tunis consisting of a shift towards enhanced winter precipitation together with rising temperatures. This novel study shows an overall rise in the proportion of small phytoplankton cells and a decreasing trend in phytoplankton diversity in the southern Mediterranean area. These findings warn of a potential decline of trophic efficiency and lesser food web stability resulting from mean size reduction and the diversity loss.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    High CO2 and warming affect microzooplankton food web dynamics in a Baltic Sea summer plankton community (2020)
    Springer
    Details
    Publication Date: 2023-02-08
    Description: Aquatic ecosystems face a multitude of environmental stressors, including warming and acidification. While warming is expected to have a pronounced effect on plankton communities, many components of the plankton seem fairly robust towards realistic end-of-century acidification conditions. However, interactions of the two stressors and the inclusion of further factors such as nutrient concentration and trophic interactions are expected to change this outcome. We investigated the effects of warming and high CO2 on a nutrient-deplete late summer plankton community from the Kiel Fjord, Baltic Sea, using a mesocosm setup crossing two temperatures with a gradient of CO2. Phytoplankton and microzooplankton (MZP) growth rates as well as biomass, taxonomic composition, and grazing rates of MZP were analysed. We observed effects of high CO2, warming, and their interactions on all measured parameters. The occurrence and direction of the effects were dependent on the phytoplankton or MZP community composition. In addition, the abundance of small-sized phytoplankton was identified as one of the most important factors in shaping the MZP community composition. Overall, our results indicate that an estuarine MZP community used to strong natural fluctuations in CO2 can still be affected by a moderate increase in CO2 if it occurs in combination with warming and during a nutrient-deplete post-bloom situation. This highlights the importance of including trophic interactions and seasonality aspects when assessing climate change effects on marine zooplankton communities.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Food Quantity and Quality Interactions at Phytoplankton–Zooplankton Interface: Chemical and Reproductive Responses in a Calanoid Copepod (2020)
    Frontiers
    Details
    Publication Date: 2023-02-08
    Description: Marine food webs form the major component of the biological pump and play a central role in the global carbon (C) cycle. Understanding the response of particular processes in marine food webs to changing environments is a prerequisite to predict changes in ecological functioning in the future ocean. Here, we experimentally assessed the effects of nitrogen:phosphorus (N:P) supply ratios (the molar ratios 10:1, 24:1, and 63:1) on elemental and biochemical quality of marine phytoplankton Rhodomonas sp., and the interactions between food quantity and quality on stoichiometric C:N:P, fatty acids (FAs) and reproductions in copepods Acartia tonsa. Overall, the stoichiometry of A. tonsa was to some extent homeostatic in response to the changing algal C:N and C:P ratios, with significant changes in C:N ratios of A. tonsa observed, especially under higher food quantities. The relative gross growth efficiencies (GGEs) for C and N (and P) were analyzed, revealing that copepods may achieve homeostasis by lowering the GGE for C while increasing it for the limiting nutrient. Egg production rates in A. tonsa were lowest on nutrient deficient diets under low food quantities. Reduced egg production rates may be attributed to the lowered GGEs for C and reduced transfer efficiency of essential FAs between phytoplankton and copepods, indicating interactive-essential effects of elements and FAs on copepod production. Our results highlight that nutrient deficiency in the environments may reduce energy transfer efficiency at the base of food webs by altering phytoplankton chemical composition, which can interact with food quantity and have implications on food web dynamics in the changing ocean.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Ocean-related global change alters lipid biomarker production in common marine phytoplankton (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: Lipids, in their function as trophic markers in food webs and organic matter source indicators in the water column and sediments, provide a tool for reconstructing the complexity of global change effects on aquatic ecosystems. It remains unclear how ongoing changes in multiple environmental drivers affect the production of key lipid biomarkers in marine phytoplankton. Here, we tested the responses of sterols, alkenones and fatty acids (FAs) in the diatom Phaeodactylum tricornutum, the cryptophyte Rhodomonas sp. and the haptophyte Emiliania huxleyi under a full-factorial combination of three temperatures (12, 18 and 24 ∘C), three N : P supply ratios (molar ratios 10 : 1, 24 : 1 and 63 : 1) and two pCO2 levels (560 and 2400 µatm) in semicontinuous culturing experiments. Overall, N and P deficiency had a stronger effect on per-cell contents of sterols, alkenones and FAs than warming and enhanced pCO2. Specifically, P deficiency caused an overall increase in biomarker production in most cases, while N deficiency, warming and high pCO2 caused nonsystematic changes. Under future ocean scenarios, we predict an overall decrease in carbon-normalized contents of sterols and polyunsaturated fatty acids (PUFAs) in E. huxleyi and P. tricornutum and a decrease in sterols but an increase in PUFAs in Rhodomonas sp. Variable contents of lipid biomarkers indicate a diverse carbon allocation between marine phytoplankton species in response to changing environments. Thus, it is necessary to consider the changes in key lipids and their consequences for food-web dynamics and biogeochemical cycles, when predicting the influence of global change on marine ecosystems.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Monitoring of cyanobacteria for water quality: doing the necessary right or wrong? (2020)
    CSIRO
    Details
    Publication Date: 2023-02-08
    Description: Cyanobacteria are an essential biological component of phytoplankton water quality assessment. However, there are some problems associated with the widely used everyday practices of sampling, estimation and use of cyanobacteria when calculating phytoplankton indices assessing water quality. Many indices were developed during the implementation of the Water Framework Directive, considered the most innovative European environmental legislation. Most indices include cyanobacteria as a composition or bloom metric. Problems with the indices concern the exclusion of most chroococcalean taxa from cyanobacterial biovolume estimations in lakes and reservoirs of the Mediterranean region, treatment of the mucilage of colonial chroococcalean taxa in biovolume estimations and overlooking of deep-water cyanobacterial blooms due to sampling depth. These problems may lead to a biased view of water quality. In this paper we argue in favour of including all cyanobacteria taxa and their mucilage in biovolume estimations and considering a sampling depth that covers deep-water maxima, such as those formed by Planktothrix rubescens or colonial chroococcalean taxa.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Variability and Community Composition of Marine Unicellular Eukaryote Assemblages in a Eutrophic Mediterranean Urban Coastal Area with Marked Plankton Blooms and Red Tides (2020)
    MDPI
    Details
    Publication Date: 2023-02-08
    Description: The Thessaloniki Bay is a eutrophic coastal area which has been characterized in recent years by frequent and intense phytoplankton blooms and red tides. The aim of the study was to investigate the underexplored diversity of marine unicellular eukaryotes in four different sampling sites in Thessaloniki Bay during a year of plankton blooms, red tides, and mucilage aggregates. High-Throughput Sequencing (HTS) was applied in extracted DNA from weekly water samples targeting the 18S rRNA gene. In almost all samples, phytoplankton blooms and/or red tides and mucilage aggregates were observed. The metabarcoding analysis has detected the known unicellular eukaryotic groups frequently observed in the Bay, dominated by Bacillariophyta and Dinoflagellata, and revealed taxonomic groups previously undetected in the study area (MALVs, MAST, and Cercozoa). The dominant OTUs were closely related to species known to participate in red tides, harmful blooms, and mucilage aggregates. Other OTUs, present also during the blooms in low abundance (number of reads), were closely related to known harmful species, suggesting the occurrence of rare taxa with potential negative impacts on human health not detectable with classical microscopy. Overall, the unicellular eukaryote assemblages showed temporal patterns rather than small-scale spatial separation responding to the variability of physical and chemical factors.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Effects of Harmful Blooms of Large-Sized and Colonial Cyanobacteria on Aquatic Food Webs (2020)
    MDPI
    Details
    Publication Date: 2023-02-08
    Description: Cyanobacterial blooms are the most important and best studied type of harmful algal blooms in fresh waters and brackish coastal seas. We here review how and to which extent they resist grazing by zooplankton, how zooplankton responds to cyanobacterial blooms and how these effects are further transmitted to fish. Size, toxicity and poor nutritional value are widespread mechanisms of grazing defense by cyanobacteria. In some cases, defenses are inducible, in some they are obligate. However, to some extent zooplankton overcome grazing resistance, partly after evolutionary adaptation. Cyanotoxins are also harmful to fish and may cause fish kills. However, some fish species feed on Cyanobacteria, are able to reduce their abundance, and grow on a cyanobacterial diet. While reduced edibility for crustacean zooplankton tends to elongate the food chain from primary producers to fish, direct feeding by fish tends to shorten it. The few available comparative studies relating fish yield to nutrients or phytoplankton provide no indication that cyanobacteria should reduce the ratio fish production: primary production.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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