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  • 1
    Book
    Book
    Omnivory in planktonic food webs : a study on the impact of mixotrophic flagellates and microzooplankton on food web dynamics and productivity (2003)
    Kiel : Institut für Meereskunde
    Details Availability
    Keywords: Dissertation ; Hochschulschrift ; Plankton ; Nahrungskette ; Plankton ; Allesfresser ; Flagellaten ; Mixotrophie ; Mikrofauna ; Zooplankton
    Type of Medium: Book
    Pages: 101 S , Ill., graph. Darst
    Series Statement: Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel 328
    RVK:
    WI 4745
    Language: English
    Note: Literaturverz. S. 89 - 99 , Zugl.: Kiel, Univ., Diss., 2003 , Zsfassung in dt. Sprache
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  • 2
    Online Resource
    Online Resource
    Omnivory in planktonic food webs : a study on the impact of mixotrophic flagellates and microzooplankton on food web dynamics and productivity (2003)
    Kiel : Inst. für Meereskunde
    Details Availability
    Keywords: Dissertation ; Hochschulschrift ; Plankton
    Description / Table of Contents: Summary ; Zs.-Fassung
    Type of Medium: Online Resource
    Pages: Online-Ressource (101 S. = 2.19 MB, Text) , Ill., graph. Darst.
    Edition: [Electronic ed.]
    Series Statement: Berichte aus dem Institut für Meereskunde an der Christian-Albrechts-Universität Kiel Nr. 328
    URL: http://eldiss.uni-kiel.de/macau/receive/dissertation_diss_825
    URL: http://nbn-resolving.de/urn:nbn:de:gbv:8-diss-8251
    URN: urn:nbn:de:gbv:8-diss-8251
    RVK:
    WI 4745
    Language: English
    Note: Zugl.: Kiel, Univ., Diss., 2003
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  • 3
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    Goldman revisited: Faster-growing phytoplankton has lower N:P and lower stoichiometric flexibility (2013)
    Association for the Sciences of Limnology and Oceanography
    In:  EPIC3Limnology and Oceanography, Association for the Sciences of Limnology and Oceanography, 58(6), pp. 2076-2088, ISSN: 0024-3590
    Details
    Publication Date: 2015-01-14
    Description: In their seminal paper, Goldman et al. suggested that phytoplankton close to maximum growth rate attains a restricted optimal N : P ratio close to the Redfield ratio of molar N : P = 16. Recently, the presence of such a global attractor for optimal phytoplankton stoichiometry has been questioned in models and empirical analyses. As the chemical composition of phytoplankton is of major importance for our understanding of global elemental cycles and biogeochemical transformations, we assembled 55 data sets of phytoplankton growth rate and biomass N : P ratios in a meta-analysis testing (1) whether phytoplankton N : P converges at high growth rates, (2) whether N : P ratios scale with growth rate, and (3) whether the optimal N : P ratios achieved at highest growth rates reflect organism traits or environmental conditions. Across systems and species, phytoplankton N : P decreased with increasing growth rate and at the same time showed decreasing variance, i.e., fast-growing phytoplankton is more P rich and has a more confined elemental composition. Optimal N : P increased with increasing N : P of available nutrients, i.e., with increasing P limitation. Other differences were rare, except cyanobacteria showed higher optimal N : P than diatoms. Understanding the role of phytoplankton in biogeochemical transformation requires modeling approaches that are stoichiometrically flexible to reflect the dynamics of growth and nutrient supply in primary producers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Applications of ecological stoichiometry for sustainable acquisition of ecosystem services (2005)
    Wiley-Blackwell
    In:  Oikos, 109 . pp. 52-62.
    Details
    Publication Date: 2017-01-31
    Description: Human activities have differentially altered biogeochemical cycling at local, regional and global scales. We propose that a stoichiometric approach, examining the fluxes of multiple elements and the ratio between them, may be a useful tool for better understanding human effects on ecosystem processes and services. The different scale of impacts of the elements carbon, nitrogen and phosphorus and the different nature of their biogeochemical cycles, imply a large variation of their stoichiometric ratios in space and time and thus divergent impacts on biota. In this paper, we examine the effects of anthropogenic perturbations on nutrient ratios in ecosystems in two examples and one case study. Altered stoichiometry in agricultural systems (example 1) can affect not only crop yield and quality but also the interactions between plants and their pollinators, pests and pathogens. Human activities have also altered stoichiometry in coastal ecosystems (example 2). Increased N loading has especially lead to increased N:P and reduced Si:N ratios, with detrimental effects on ecosystem services derived from coastal pelagic food webs, such as fish yield and water quality. The terrestrial–aquatic linkage in stoichiometric alterations is illustrated with a case study, the Mississippi River watershed, where anthropogenic activities have caused stoichiometric changes that have propagated through the watershed into the northern Gulf of Mexico. Coupled with altered stoichiometric nutrient inputs are the inherent differences in variation and sensitivity of different ecosystems to anthropogenic disturbance. Furthermore, the connections among the components of a watershed may result in downstream cascades of disrupted functioning. Applying a multiple element perspective to understanding and addressing societal needs is a new direction for both ecological stoichiometry and sustainability.
    Type: Article , PeerReviewed
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  • 5
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    Diversity and community biomass depend on dispersal and disturbance in microalgal communities (2010)
    Springer
    In:  Hydrobiologia, 653 . pp. 65-78.
    Details
    Publication Date: 2018-07-02
    Description: The evidence for species diversity effects on ecosystem functions is mainly based on studies not explicitly addressing local or regional processes regulating coexistence or the importance of community structure in terms of species evenness. In experimental communities of marine benthic microalgae, we altered the successional stages and thus the strength of local species interactions by manipulating rates of dispersal and disturbance. The treatments altered realized species richness, evenness and community biomass. For species richness, dispersal mattered only at high disturbance rates; when opening new space, dispersal led to maximized richness at intermediate dispersal rates. Evenness, in contrast, decreased with dispersal at low or no disturbance, i.e. at late successional stages. Community biomass showed a nonlinear hump-shaped response to increasing dispersal at all disturbance levels.We found a positive correlation between richness and biomass at early succession, and a strong negative correlation between evenness and biomass at late succession. In early succession both community biomass and richness depend directly on dispersal from the regional pool, whereas the late successional pattern shows that if interactions allow the most productive species to become dominant, diverting resources from this species (i.e. higher evenness) reduces production. Our study emphasizes the difference in biodiversity–function relationships over time, as different mechanisms contribute to the regulation of richness and evenness in early and late successional stages.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1007/s10750-010-0349-x
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  • 6
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    Stoichiometry of Fe, Mn and Co in the marine diazotroph Crocosphaera subtropica ATCC51142 in Fe- and P-limited continuous cultures (2020)
    Inter Research
    Details
    Publication Date: 2023-02-08
    Description: We investigated trace element stoichiometries of the nitrogen-fixing marine cyanobacterium Crocosphaera subtropica ATCC51142 under steady-state growth conditions. We utilized exponentially fed batch cultures and varied iron (Fe) concentrations to establish nutrient limitation in C. subtropica growing at a constant growth rate (0.11 d -1 ). No statistical difference in cell density, chlorophyll a , particulate organic carbon (C), nitrogen (N) and phosphorus (P) were observed between consecutive days after Day 14, and cultures were assumed to be at steady state with respect to growth for the remaining 11 d of the experiment. Cultures were limited by P in the highest Fe treatment (41 nmol l -1 ) and by Fe in the 2 lower-concentration Fe treatments (1 and 5 nmol l -1 ). Cell size and in vivo fluorescence changed throughout the experiment in the 1 nmol l -1 Fe treatment, suggesting ongoing acclimation of C. subtropica to our lowest Fe supply. Nevertheless, Fe:C ratios were not significantly different between the Fe treatments, and we calculated an average (±SD) Fe:C ratio of 32 ± 14 µmol mol -1 for growth at 0.11 d -1 . Steady-state P-limited cells had lower P quotas, whilst Fe-limited cells had higher manganese (Mn) and cobalt (Co) quotas. We attribute the increase in Mn and Co quotas at low Fe to a competitive effect resulting from changes in the supply ratio of trace elements. Such an effect has implications for variability in elemental stoichiometry in marine phytoplankton, and potential consequences for trace metal uptake and cycling in marine systems.
    Type: Article , PeerReviewed
    Format: text
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  • 7
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    Trophic switches in pelagic systems (2019)
    Elsevier
    In:  Current Opinion in Systems Biology, 13 . pp. 108-114.
    Details
    Publication Date: 2022-01-31
    Description: Ecological studies need experimentation to test concepts and to disentangle causality in community dynamics. While simple models have given substantial insights into population and community dynamics, recent ecological concepts become increasingly complex. The globally important pelagic food web dynamics are well suited to test complex ecological concepts. For instance, trophic switches of individual organisms within pelagic food webs can elongate food webs or shift the balance between autotroph and heterotroph carbon fluxes. Here, we summarize results from mesocosm experiments demonstrating how environmental drivers result in trophic switches of marine phytoplankton and zooplankton communities. Such mesocosm experiments are useful to develop and test complex ecological concepts going beyond trophic level–based analyses, including diversity, individual behavior, and environmental stochasticity
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1016/j.coisb.2018.11.006
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  • 8
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    Effects of microzooplankton and mixotrophy in an experimental planktonic food web (2004)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 49 . pp. 1435-1445.
    Details
    Publication Date: 2019-09-23
    Description: Microzooplankton have received increased attention as an important trophic link between the microbial loop and calanoid copepods. On the basis of food size spectra overlap in some microzooplankton groups and calanoid copepods, however, such microzooplankton could function as competitors rather than as food for calanoid copepods (intraguild prey). Mixotrophic flagellates presumably represent a link between the microbial loop and the micro and mesozooplankton. We investigated the effects of microzooplankton and mixotrophy by altering the presence of a heterotrophic dinoflagellate and of a mixotrophic nanoflagellate in artificial food webs with calanoid copepods as terminal consumers. Overall system productivity was manipulated by two levels of nutrient enrichment. The heterotrophic dinoflagellate drastically reduced the nanophytoplankton and enhanced the reproduction of the copepods, suggesting that its role as a competitor is negligible compared to its function as a trophic link. In spite of the presence of heterotrophic nanoflagellates, the mixotroph had a strong negative effect on the picophytoplankton and (presumably) on bacterial biomass. At the same time, the mixotroph enhanced the atomic C:N ratio of the seston biomass, indicating a higher efficiency in overall primary production. Copepod reproduction was enhanced in the presence of the mixotrophic nanoflagellate. Results did not support predictions of the intraguild predation theory: The ratios of the intraguild predators and their preys were not affected by overall system productivity
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lo.2004.49.4_part_2.1435
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  • 9
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    Performance of sinking and nonsinking phytoplancton taxa in a gradient of mixing depths (2003)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 48 (5). pp. 1903-1912.
    Details
    Publication Date: 2014-01-30
    Description: According to a recent dynamical model, the depth of a well-mixed water column should have contrasting effects on the abundances of sinking and nonsinking phytoplankton taxa. Because of increasing light limitation, nonsinking taxa should decline monotonically with increasing mixing depth, and because of sinking loss limitation at low mixing depths, sinking taxa should peak at intermediate mixing depths. Along a gradient of mixing depths, the position of this maximum should increase with increasing taxon-specific sinking velocity and decrease with increasing background turbidity. In two field-enclosure experiments, we investigated the effects of mixing depth and background turbidity on a variety of sinking and nonsinking phytoplankton taxa. We exposed the natural, 100-µm screened phytoplankton community of a clear, unproductive, but silica-rich lake to a gradient of mixing depths (1.5- 15 m) during 4-6 weeks. To mimic two different background turbidities, the transparent enclosure walls were surrounded by either white or black foliage. Although diatoms suffered from high sedimentation losses at low mixing depths, they dominated biomass at all mixing depths throughout both experiments. Results were largely in accordance with model predictions. Specific gross growth rates of most common taxa were negatively related to mixing depth. In both experiments, the abundances of most sinking taxa showed a unimodal pattern along the mixing depth gradient, while two of three motile taxa declined monotonically with mixing depth. The depths where these taxa reached their maximal abundances were positively related to taxon-specific sinking velocity and negatively related to background turbidity.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.4319/lo.2003.48.5.1903
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  • 10
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    Phytoplankton, light, and nutriets in a gradient of mixing depths: field experiments (2002)
    Wiley
    In:  Ecology, 83 (2). pp. 399-411.
    Details
    Publication Date: 2017-02-17
    Description: We studied the effects of water column mixing depth and background turbidity on phytoplankton biomass, light climate, and nutrients in two field enclosure experiments designed to test predictions of a dynamical model. In 1997 and 1998, we created gradients of mixing depth by enclosing the 100-μm-filtered phytoplankton community of a phosphorus-deficient lake in cylindrical plastic bags of varying depth (1.5–15 m) which were continuously mixed. To mimic different levels of background turbidity, we surrounded the transparent enclosure walls with a layer of opaque white (1997) or black (1998) plastic. The experiments were run for 4 wk (1997) and 6 wk (1998). The results supported two key assumptions of the model: specific production and specific sedimentation losses both decreased with increasing mixing depth. At all mixing depths, fast-sinking diatoms dominated the communities. In accordance with model predictions, algal biomass concentration and standing stock (summed over the mixed layer) showed a unimodal relationship to mixing depth when background turbidity was high (1998). When background turbidity was lower (1997), only the ascending limbs of the corresponding relationships were found, which supports the prediction that the mixing depth at which biomass peaks (i.e., becomes predominantly limited by light) increases with decreasing background turbidity. Also in accordance with predictions, light intensity at the bottom of the mixed layer decreased with increasing mixing depth and with increasing background turbidity. Finally, the data supported only the ascending limbs of the predicted inverse unimodal relationships among mixing depth and dissolved inorganic and total water column phosphorus. The absence of descending limbs in these relationships at low mixing depths was probably due to deviations of the experimental systems from two model assumptions. First, the remineralization rate of sedimented phosphorus may have been too slow to equilibrate with sedimentation losses over the experimental periods. Second, biomass yield per unit nutrient (the ratio of seston carbon to phosphorus) was not constant, but decreased with increasing mixing depth. To our knowledge, these are the first field experiments in which the effects of mixing depth on phytoplankton and its resources have been investigated systematically along a large gradient.
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