Changes in nutrient concentration and water level affect the microbial loop: a 6‑month mesocosm experiment
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Kuupäev
2023
Kättesaadav alates
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Springer
Abstrakt
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 in fully
mixed shallow lakes, we manipulated water depth
and nutrients in a lake mesocosm experiment in north
temperate Estonia and followed the microbial community dynamics over a 6-month period. The experiment was carried out in Lake Võrtsjärv—a large,
shallow eutrophic lake. 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 the biomasses of bacterial and heterotrophic nanoflagellates
(HNF) (RM-ANOVA, p < 0.05). Nutrients affected
positively and depth negatively the mean size of individual HNF and ciliate cells (RM-ANOVA; p < 0.05).
The interactions of depth and nutrients affected
positively the biomass of bacterivorous and bacteriherbivorous ciliates and negatively the biomass of
predaceous ciliates (RM-ANOVA; p < 0.05). 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.
This work was supported by EU 7FP Theme 6 projects MARS (Managing Aquatic ecosystems and water Resources under multiple Stress, Contract No. 603378), Estonian Ministry of Education and Research (IUT 21-02), Estonian Research Council Grant PRG709, Estonian University of Life Sciences (P190258PKKH) and Swiss Grant for Programme "Enhancing public environmental monitoring capacities". This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 951963. Erik Jeppesen was also supported by the TÜBITAK program BIDEB2232 (Project 118C250). Josef Hejzlar was also supported by the Czech Science Foundation (Project 22-33245S). We thank Anne Mette Poulsen for valuable English editions.
This work was supported by EU 7FP Theme 6 projects MARS (Managing Aquatic ecosystems and water Resources under multiple Stress, Contract No. 603378), Estonian Ministry of Education and Research (IUT 21-02), Estonian Research Council Grant PRG709, Estonian University of Life Sciences (P190258PKKH) and Swiss Grant for Programme "Enhancing public environmental monitoring capacities". This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 951963. Erik Jeppesen was also supported by the TÜBITAK program BIDEB2232 (Project 118C250). Josef Hejzlar was also supported by the Czech Science Foundation (Project 22-33245S). We thank Anne Mette Poulsen for valuable English editions.
Kirjeldus
Märksõnad
eutrophication, protozoa, bacteria, heterotrophic nanoflagellates, top-down and bottom-up control, articles