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  • 1
    Online Resource
    Online Resource
    Biogeochemistry of N, P and SI in the Gulf of Riga surface sediments: Implications of seasonally changing factors
    Elsevier BV ; 2015
    In:  Continental Shelf Research Vol. 105 ( 2015-08), p. 112-120
    Details
    In: Continental Shelf Research, Elsevier BV, Vol. 105 ( 2015-08), p. 112-120
    Type of Medium: Online Resource
    ISSN: 0278-4343
    URL: Article
    DOI: 10.1016/j.csr.2015.06.008
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2015
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    detail.hit.zdb_id: 780256-0
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  • 2
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    Metabolism and foraging strategies of mid‐latitude mesozooplankton during cyanobacterial blooms as revealed by fatty acids, amino acids, and their stable carbon isotopes
    Wiley ; 2019
    In:  Ecology and Evolution Vol. 9, No. 17 ( 2019-09), p. 9916-9934
    Details
    In: Ecology and Evolution, Wiley, Vol. 9, No. 17 ( 2019-09), p. 9916-9934
    Abstract: Increasing sea surface temperatures (SST) and blooms of lipid‐poor, filamentous cyanobacteria can change mesozooplankton metabolism and foraging strategies in marine systems. Lipid shortage and imbalanced diet may challenge the build‐up of energy pools of lipids and proteins, and access to essential fatty acids (FAs) and amino acids (AAs) by copepods. The impact of cyanobacterial blooms on individual energy pools was assessed for key species temperate Temora longicornis and boreal Pseudo‐/Paracalanus spp. that dominated field mesozooplankton communities isolated by seasonal stratification in the central Baltic Sea during the hot and the cold summer. We looked at (a) total lipid and protein levels, (b) FA trophic markers and AA composition, and (c) compound‐specific stable carbon isotopes (δ 13 C) in bulk mesozooplankton and in a subset of parameters in particulate organic matter. Despite lipid‐poor cyanobacterial blooms, the key species were largely able to cover both energy pools, yet a tendency of lipid reduction was observed in surface animals. Omni‐ and carnivory feeding modes, FA trophic makers, and δ 13 C patterns in essential compounds emphasized that cyanobacterial FAs and AAs have been incorporated into mesozooplankton mainly via feeding on mixo‐ and heterotrophic (dino‐) flagellates and detrital complexes during summer. Foraging for essential highly unsaturated FAs from (dino‐) flagellates may have caused night migration of Pseudo‐/Paracalanus spp. from the deep subhalocline waters into the upper waters. Only in the hot summer (SST 〉 19.0°C) was T. longicornis submerged in the colder subthermocline water (~4°C). Thus, the continuous warming trend and simultaneous feeding can eventually lead to competition on the preferred diet by key copepod species below the thermocline in stratified systems. A comparison of δ 13 C patterns of essential AAs in surface mesozooplankton across sub‐basins of low and high cyanobacterial biomasses revealed the potential of δ 13 C‐AA isoscapes for studies of commercial fish feeding trails across the Baltic Sea food webs.
    Type of Medium: Online Resource
    ISSN: 2045-7758 , 2045-7758
    URL: Issue
    URL: Article
    DOI: 10.1002/ece3.v9.17
    DOI: 10.1002/ece3.5533
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2635675-2
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  • 3
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    Stable isotope analysis in food web research: Systematic review and a vision for the future for the Baltic Sea macro-region
    Springer Science and Business Media LLC ; 2023
    In:  Ambio Vol. 52, No. 2 ( 2023-02), p. 319-338
    Details
    In: Ambio, Springer Science and Business Media LLC, Vol. 52, No. 2 ( 2023-02), p. 319-338
    Abstract: Food web research provides essential insights into ecosystem functioning, but practical applications in ecosystem-based management are hampered by a current lack of knowledge synthesis. To address this gap, we provide the first systematic review of ecological studies applying stable isotope analysis, a pivotal method in food web research, in the heavily anthropogenically impacted Baltic Sea macro-region. We identified a thriving research field, with 164 publications advancing a broad range of fundamental and applied research topics, but also found structural shortcomings limiting ecosystem-level understanding. We argue that enhanced collaboration and integration, including the systematic submission of Baltic Sea primary datasets to stable isotope databases, would help to overcome many of the current shortcomings, unify the scattered knowledge base, and promote future food web research and science-based resource management. The effort undertaken here demonstrates the value of macro-regional synthesis, in enhancing access to existing data and supporting strategic planning of research agendas.
    Type of Medium: Online Resource
    ISSN: 0044-7447 , 1654-7209
    URL: Article
    DOI: 10.1007/s13280-022-01785-1
    RVK:
    AR 10100
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 120759-3
    detail.hit.zdb_id: 2040524-8
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  • 4
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    Strategies of amino acid supply in mesozooplankton during cyanobacteria blooms: a stable nitrogen isotope approach
    Wiley ; 2018
    In:  Ecosphere Vol. 9, No. 3 ( 2018-03)
    Details
    In: Ecosphere, Wiley, Vol. 9, No. 3 ( 2018-03)
    Abstract: Knowledge of how zooplankton can utilize cyanobacteria to sustain their nitrogen (N) demand for essential compounds like amino acids ( AA s) is a key to predicting responses of higher trophic levels in terms of production and food web structure to future enhanced water column stratification. We explored the natural abundances of bulk N and AA ‐specific nitrogen isotopes (δ 15 N) in particulate organic matter and mesozooplankton size‐fraction samples from three vertically separated water bodies in the central Baltic Sea during two summertime cyanobacteria blooms. The combination of plankton community and isotope data together with environmental variables helped to identify a mechanism of diazotrophic AA supply (synthesized during N 2 fixation) for mesozooplankton, that largely depended on the sea surface temperature which regulated the access to the diazotrophic N‐based food web in the surface water ( SW ). We found that in the warmer summer, thermophilic cladocerans (e.g., Bosmina spp.) benefited most from diazotrophic AA s in the SW (19.8°C), while only in the colder summer, temperate copepods (e.g., Temora longicornis ) ascended from the subjacent winter water into the SW (16.2°C) and incorporated diazotrophic AA s. Trophic position estimates based on the phenylalanine and glutamic acid δ 15 N signatures revealed that the diazotrophic AA supply into mesozooplankton was mainly indirect via feeding on mixo‐ and heterotrophic diets. Significantly enriched δ 15 N signatures in phenylalanine in the deep mesozooplankton (mainly copepods of Pseudo‐ and Paracalanus spp.) from the bottom water ( BW ) that was a region of the suboxic zone point to a reliance on a local food web. Mesozooplankton in the BW was feeding on diets of heterotrophic origin and probably profited from the heterotrophic re‐synthesis of AA s originating from sinking organic matter, as well as from the indirect incorporation of de novo synthesized AA s that most likely originated from chemoautotrophic bacteria or archaea communities in the suboxic zone. Our findings suggest that indirect feeding on diazotrophs and chemoautotrophs will be principal ways of amino acid supply for zooplankton in future enhanced stratified aquatic systems. Only a relatively small increase in temperature may restrict temperate key species from diazotrophic N‐based food webs in the mixed layer.
    Type of Medium: Online Resource
    ISSN: 2150-8925 , 2150-8925
    URL: Issue
    URL: Article
    DOI: 10.1002/ecs2.2018.9.issue-3
    DOI: 10.1002/ecs2.2135
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2572257-8
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  • 5
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    Bidirectional energy subsidies for fish in river mouths of a large lake as revealed by stable isotopes and fatty acids
    Wiley ; 2024
    In:  Limnology and Oceanography
    Details
    In: Limnology and Oceanography, Wiley
    Abstract: Freshwater river mouths may facilitate cross‐habitat resource use and bidirectional subsidization through (a) active cross‐habitat movement by consumers like fish and (b) water and material movement both downstream, from tributary to nearshore lake, and in the opposite direction due to backflow processes. Despite potential importance of freshwater river mouths, relative contributions of lentic and tributary energy sources to fishes along these ecotones remain understudied, in part because measuring cross‐habitat subsidization is not straightforward. We assessed cross‐habitat subsidization of three fish consumers round goby ( Neogobius malanostomus ), yellow perch ( Perca flavescens ), and alewife ( Alosa psuedoharengus ) in three river mouths of Lake Michigan, USA. Specifically, we (a) measured stable isotope ratios (δ 13 C, δ 15 N, δ 2 H, δ 18 O) in ambient water, bivalve shells, potential invertebrate prey, and fish soft tissue, and we assessed fish nutritional status based on essential fatty acid composition, and (b) estimated Bayesian ellipses and mixing models including either two (δ 13 C‐δ 15 N) or three (δ 13 C‐δ 15 N‐δ 2 H) isotope ratios. Results revealed evidence of bidirectional habitat subsidies for all fishes, but energy subsidies varied by species and across river mouths; likely related to differences in species‐specific behavior and hydrologic differences among river mouths. Relative to nearshore oligotrophic Lake Michigan, fish in productive tributary environments contained relatively low essential fatty acid content, suggesting a possible trade‐off between prey quantity and quality across habitats. This study advances our understanding of resource connectivity in lake ecosystems and the combined use of multiple stable isotopes (including mixing models) and fatty acids to document cross‐habitat subsidies along freshwater ecotones.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Article
    DOI: 10.1002/lno.12500
    Language: English
    Publisher: Wiley
    Publication Date: 2024
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
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  • 6
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    Nutrient turnover at the hypoxic boundary: flux measurements and model representation for the bottom water environment of the Gulf of Riga, Baltic Sea**The study was supported by the ERAF project ‘Development of a mechanistic model of the Gulf of Riga ecosystem in support of an efficient national policy to ensure the protection of the Baltic Sea and to promote the sustainable use of its ecosystem’ (Ref. Nr. 2010/0287/2DP/2.1.1.1.0/10/APIA/VIAA/040) and the state research programme ‘Impact of climate change on Latvia’s water environment – KALME’.
    Elsevier BV ; 2014
    In:  Oceanologia Vol. 56, No. 4 ( 2014), p. 711-735
    Details
    In: Oceanologia, Elsevier BV, Vol. 56, No. 4 ( 2014), p. 711-735
    Type of Medium: Online Resource
    ISSN: 0078-3234
    URL: Article
    DOI: 10.5697/oc.56-4.711
    Language: Polish
    Publisher: Elsevier BV
    Publication Date: 2014
    detail.hit.zdb_id: 120206-6
    detail.hit.zdb_id: 1474539-2
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  • 7
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    Stratification, nitrogen fixation, and cyanobacterial bloom stage regulate the planktonic food web structure
    Wiley ; 2019
    In:  Global Change Biology Vol. 25, No. 3 ( 2019-03), p. 794-810
    Details
    In: Global Change Biology, Wiley, Vol. 25, No. 3 ( 2019-03), p. 794-810
    Abstract: Changes in the complexity of planktonic food webs may be expected in future aquatic systems due to increases in sea surface temperature and an enhanced stratification of the water column. Under these conditions, the growth of unpalatable, filamentous, N 2 ‐fixing cyanobacterial blooms, and their effect on planktonic food webs will become increasingly important. The planktonic food web structure in aquatic ecosystems at times of filamentous cyanobacterial blooms is currently unresolved, with discordant lines of evidence suggesting that herbivores dominate the mesozooplankton or that mesozooplankton organisms are mainly carnivorous. Here, we use a set of proxies derived from amino acid nitrogen stable isotopes from two mesozooplankton size fractions to identify changes in the nitrogen source and the planktonic food web structure across different microplankton communities. A transition from herbivory to carnivory in mesozooplankton between more eutrophic, near‐coastal sites and more oligotrophic, offshore sites was accompanied by an increasing diversity of microplankton communities with aging filamentous cyanobacterial blooms. Our analyses of 124 biotic and abiotic variables using multivariate statistics confirmed salinity as a major driver for the biomass distribution of non‐N 2 ‐fixing microplankton species such as dinoflagellates. However, we provide strong evidence that stratification, N 2 fixation, and the stage of the cyanobacterial blooms regulated much of the microplankton diversity and the mean trophic position and size of the metabolic nitrogen pool in mesozooplankton. Our empirical, macroscale data set consistently unifies contrasting results of the dominant feeding mode in mesozooplankton during blooms of unpalatable, filamentous, N 2 ‐fixing cyanobacteria by identifying the at times important role of heterotrophic microbial food webs. Thus, carnivory, rather than herbivory, dominates in mesozooplankton during aging and decaying cyanobacterial blooms with hitherto uncharacterized consequences for the biogeochemical functions of mesozooplankton.
    Type of Medium: Online Resource
    ISSN: 1354-1013 , 1365-2486
    URL: Issue
    URL: Article
    DOI: 10.1111/gcb.2019.25.issue-3
    DOI: 10.1111/gcb.14546
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2020313-5
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  • 8
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    De novo amino acid synthesis and turnover during N 2 fixation
    Wiley ; 2018
    In:  Limnology and Oceanography Vol. 63, No. 3 ( 2018-05), p. 1076-1092
    Details
    In: Limnology and Oceanography, Wiley, Vol. 63, No. 3 ( 2018-05), p. 1076-1092
    Abstract: Cyanobacteria are the main autotrophs and N 2 ‐fixing (diazotrophic) organisms in large parts of the oligotrophic global ocean, where generally all heterotrophic production depends on their activity. Amino acids (AAs) from cyanobacteria are essential macronutrients for these heterotrophic food webs, yet little is known about the de novo synthesis of AAs during N 2 fixation. Through a combination of bulk and amino acid nitrogen (AAN) specific analyses of field based N 2 fixation experiments, we demonstrate that the de novo synthesis of 13 AAs accounted for the majority of bulk N 2 fixation rates at four stations in the central Baltic Sea in July 2015. Slow AA turnover times of 87 ± 14 d coincided with low phosphate concentrations and high cell‐carbon biomasses of unicellular cyanobacteria. Very fast turnover times of 17 ± 3 d coincided with high phosphate concentrations and undecayed Nodularia spumigena cells, but unexpectedly also with phosphate depletion and decayed N. spumigena cells. In a decayed bloom, volumetric N 2 fixation rates into AAN provided a much better estimate of the net incorporation of N 2 into biomass than fixation into bulk nitrogen that rather reflected gross N 2 fixation. In an undecayed bloom, the turnover times of 13 AAs can be predicted from a single bulk N 2 fixation rate. This is the first direct evidence that the very late, decayed stage of a cyanobacteria bloom can be a flashpoint of very fast AA turnover during N 2 fixation with hitherto uncharacterized consequences for heterotrophic food webs and diazotroph N inputs to the global ocean.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    URL: Article
    DOI: 10.1002/lno.v63.3
    DOI: 10.1002/lno.10755
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
    SSG: 12
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