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TREICLAKE

Selle valdkonna püsiv URIhttp://hdl.handle.net/10492/7299

"Towards Research Excellence and Innovation Capacity in Studing Lake Ecosystems Functional Structures and Climate Change Impact " (1.01.2021−31.12.2023); Principal investigator: Lea Tuvikene, Estonian University of Life Sciences, Institute of Agricultural and Environmental Sciences, Chair of Hydrobiology and Fishery. Funder: European Commission

Sirvi

Sirvi TREICLAKE Autor "Centre for Limnology" järgi

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  • Pisipilt
    Kirje
    Changes in nutrient concentration and water level affect the microbial loop: a multi-seasonal mesocosm experiment : [submitted version]
    (Springer, 2023) Zingel, Priit; Jeppesen, Erik; Nõges, Tiina; Hejzlar, Josef; Tavşanoğlu, Ülkü Nihan; Papastergiadou, Eva; Scharfenberger, Ulrike; Agasild, Helen; Centre for Limnology
    Eutrophication and lake depth are of key importance in structuring lake ecosystems. To elucidate the effect of contrasting nutrient concentrations and water levels on the microbial community, we manipulated water depth and nutrients in a mesocosm experiment in north temperate Estonia and followed the microbial community dynamics during a 6-month period. We used two nutrient levels crossed with two water depths, each represented by four replicates. We found treatment effects on the microbial food web structure, with nutrients having a positive and water depth a negative effect on bacterial biomass, heterotrophic nanoflagellates (HNF) and metazooplankton biomass. Nutrients and water depth had both positive impacts on phytoplankton biomass. Bacterivorous ciliates had lowest biomass in shallow and nutrient rich mesocosms, whilst predaceous ciliates had highest biomass here, influencing trophic interactions in the microbial loop. Overall, increased nutrient concentrations and decreased water level resulted in an enhanced bacterial biomass and a decrease in their main grazers. These differences appeared to reflect distinctive regulation mechanisms inside the protozoan community and in the trophic interactions in the microbial loop community.
  • Pisipilt
    Kirje
    The comparison of the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of northern temperate lakes
    (Estonian Academy Publishers, 2022) Karus, Katrit; Zagars, Matiss; Agasild, Helen; Feldmann, Tõnu; Tuvikene, Arvo; Puncule, Linda; Zingel, Priit; Chair of Hydrobiology and Fishery; Centre for Limnology
    We studied the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of four different lakes – one Latvian (Auciema) and three Estonian (Akste, Kaiavere, and Prossa). Altogether, 162 perch larvae (81 from both habitats) were collected to estimate the diet composition of gathered larval specimens in spring (2019) using gut content analysis via epifluorescence microscopy. Attention was paid particularly to the question how does the larval perch food composition differ in pelagic and littoral habitats. We hypothesized that the consumption of zooplankton is higher and the larval condition is better in littoral habitats. We assessed the feeding on both protozoo- (ciliates) and metazooplankton and applied multiple indices (Hurlbert’s standardized niche breadth, Ivlev’s selectivity and relative importance index) to evaluate, respectively, the larval fish prey importance, feeding homogeneity and strategies. The results showed that larval length and weight were slightly higher and body condition was slightly better in the lakes’ littoral habitats. The feeding niche of perch larvae was narrower in the littoral, which can indicate more favourable feeding conditions in littoral than lake pelagic habitats. While the small cladocerans (Bosmina longirostris Müller) were generally the preferred and important food objects, ciliates were avoided and consumed only when their share in the total zooplankton biomass was >40%. However, in shortage of cladocerans, ciliates could be vitally important food objects for perch larvae.