The role of planktonic ciliates in lake ecosystems

http://www.ester.ee/record=b4336574~S1*es

Keystone species Chydorus sphaericus in shallow eutrophic Lake Võrtsjärv (Estonia) – 56 years of continuous zooplankton monitoring and research

Presentation at the 11th International Shallow Lakes Conference, Estonia 11.-16.06.2023.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963, by Estonian Ministry of the Environment through the state monitoring programme, and also from the Estonian Research Council grant PRG1167.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963, by Estonian Ministry of the Environment through the state monitoring programme, and also from the Estonian Research Council grant PRG1167

How warming and other stressors affect zooplankton abundance, biomass and community composition in shallow eutrophic lakes

We aimed to investigate the influence of environmental factors and predict zooplankton biomass and abundance in shallow eutrophic lakes. We employed time series of zoo- plankton and environmental parameters that were measured monthly during 38 years in a large, shallow eutrophic lake in Estonia to build estimates of zooplankton community metrics (cladocerans, copepods, rotifers, ciliates). The analysis of historical time series revealed that air temperature was by far the most important variable for explaining zooplankton biomass and abundance, followed, in decreasing order of importance, by pH, phytoplankton biomass and nitrate concentration. Models constructed with the best predicting variables explained up to 71% of zooplankton biomass variance. Most of the predictive variables had opposing or antagonistic interactions, often mitigating the effect of temperature. In the second part of the study, three future climate scenarios were developed following different Intergovernmental Panel on Climate Change (IPCC) tem- perature projections and entered into an empirical model. Simulation results showed that only a scenario in which air temperature stabilizes would curb total metazooplankton biomass and abundance. In other scenarios, metazooplankton biomass and abundance would likely exceed historical ranges whereas ciliates would not expand. Within the metazooplankton community, copepods would increase in biomass and abundance, whereas cladocerans would lose in biomass but not in abundance. These changes in the zooplankton community will have important consequences for lake trophic structure and ecosystem functioning.This research was supported by the Estonian Research Council Grants PSG32, PRG709 and institutional research funding IUT 21-2 of the Estonian Ministry of Education and Research.This research was supported by the Estonian Research Council Grants PSG32, PRG709 and institutional research funding IUT 21-2 of the Estonian Ministry of Education and Research

Prey selection and growth in 0+ Eurasian perch Perca fluviatilis L. in littoral zones of seven temperate lakes

We studied the relationships between the planktonic food base and feeding patterns of juvenile mid-summer/ early autumn Eurasian perch Perca fluviatilis L., a common predatory freshwater fish in large parts of Europe and Asia. The feeding of 0+ perch was studied during summer and autumn in littoral habitats of seven lakes with different environmental conditions –four Latvian (Auciema, Riebinu, Vārzgūnes, Laukezers) and three Estonian (Kaiavere, Prossa and Akste) lakes. Simultaneously, the abundance, biomass and structure of zooplankton communities were examined. We focused on the littoral areas because many studies in lakes suggest that littoral habitats are particularly important for 0+ fish growth and survival. We were interested in the question: can the diet and growth of 0+ perch be explained by zooplankton community structure? We also presumed that if the amount of zooplankton is low, more benthic invertebrates will be consumed by 0+ perch. Opposite to expectations, we found that zooplankton always counted for over 90% of diet biomass in perch. There were also clear correlations between the zooplankton biomass in a given lake, the zooplankton biomass in 0+ perch stomachs, and the fish growth rate. The study also suggested that nutrient enrichment can positively impact the 0+ perch feeding conditions in lakes.The project is financed by the European Regional Development Fund, the State budget of the Republic of Latvia and the foundation “Institute for Environmental Solutions”. Funding for this project was also provided by the European Union‘s Horizon 2020 research and innovation programme under Grant Agreement No. 951963 (TREICLAKE “Towards Research Excellence and Innovation Capacity in Studying Lake Ecosystems Functional Structures and Climate Change Impact”).The project is financed by the European Regional Development Fund, the State budget of the Republic of Latvia and the foundation “Institute for Environmental Solutions”. Funding for this project was also provided by the European Union‘s Horizon 2020 research and innovation programme under Grant Agreement No. 951963 (TREICLAKE “Towards Research Excellence and Innovation Capacity in Studying Lake Ecosystems Functional Structures and Climate Change Impact”)

Predicting multiple stressor effect on zooplankton abundance, biomass and community composition in two large eutrophic lakes : [presentation]

Presentation at the BIOGEOMON 2022, 10th International Symposium on Ecosystem Behavior, June 26–30, 2022, Tartu, Estonia.We are grateful to Tartu Environmental Research Ltd (Estonia) for water chemistry data and to the Estonian Environment Board for providing long-term air temperature data and supporting lake monitoring. This research was financed by Estonian Research Council Grant PRG709, PRG1167, and institutional research funding P210160PKKH of the Estonian Ministry of Education and Research. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. Data collection within the frames of the state monitoring programme were supported by the Estonian Ministry of the Environment

Larval and juvenile perch feeding in some Estonian and Latvian study lakes : [poster]

The presentation took place at the Lahti Lakes 2021 Symposium.The research is a part of the project „Fish feeding conditions in lakes with different planktonic food web structure and macrovegetation “(MICROFISH), No.1.1.1.2/VIAA/1/18/301. Agreement with State Education Development Agency of the Republic of Latvia No. Programme number 1.1.1.2/16/I/001. The project has received funding from the European Regional Development Fund, from the State budget of the Republic of Latvia, from the foundation „Institute for Environmental Solutions” and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. Greatest thanks to PhD Priit Zingel.The research is a part of the project „Fish feeding conditions in lakes with different planktonic food web structure and macrovegetation “(MICROFISH), No.1.1.1.2/VIAA/1/18/301. Agreement with State Education Development Agency of the Republic of Latvia No. Programme number 1.1.1.2/16/I/001. The project has received funding from the European Regional Development Fund, from the State budget of the Republic of Latvia, from the foundation „Institute for Environmental Solutions” and from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. Greatest thanks to PhD Priit Zingel

Changes in nutrient concentration and water level affect the microbial loop: a multi-seasonal mesocosm experiment

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.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).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)

The influence of macrophyte ecological groups on food web components of temperate freshwater lakes

Aquatic macrophyte taxonomic composition, species abundance and cover determine the physical structure, complexity and heterogeneity of aquatic habitats – the structuring role of macrophytes. These traits influence richness, distribution, feeding and strength of the relationships between food web communities in lakes. The aim of this study was to determine how lakes with different dominating macrophyte ecological groups affect planktonic food web components, emphasising the influence on young of year (YOY) fish and large (≥1 +) fish community. We hypothesised that different dominating macrophyte ecological groups have different structural effects on food web components and YOY fish growth, abundance and feeding. Studied lakes categorised into three different macrophyte ecological groups – lakes dominated by emergent, floating+floating-leaved or submerged vegetation. We found that all dominating ecological groups had a strong influence on plankton communities (except heterotrophic bacterioplankton and nanoflagellates), YOY fish and large fish. Floating-leaved plant dominance was positively related to planktonic food web structure and YOY fish weight, length, abundance and the consumption of zooplankton as a prey of all major species of YOY fishes. Larger fish tended to favour the presence of emergent vegetation. This conclusion has important implications for local managers and conservationists in respect to the maintenance and protection of littoral habitats and fish resources.The project is financed by the European Regional Development Fund, the State budget of the Republic of Latvia and the foundation “Institute for Environmental Solutions”. Also, this project has received funding from the European Union‘s Horizon 2020 research and innovation programme under Grant Agreement No. 951963.The project is financed by the European Regional Development Fund, the State budget of the Republic of Latvia and the foundation “Institute for Environmental Solutions”. Also, this project has received funding from the European Union‘s Horizon 2020 research and innovation programme under Grant Agreement No. 951963

A Future Tale of Two Winters? Sediment-water interface nitrogen dynamics in Lake Võrtsjärv (Estonia) during the ice-free winter 2019/2020 : [presentation]

The presentation took place at the Lahti Lakes 2021 Symposium.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 95196. Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 95196. Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”

11th International Shallow Lakes Conference Estonia 11-16 June 2023 : [opening presentation]

The presentation took place at the 11th International Shallow Lakes Conference.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963