Post-soviet changes in nitrogen and phosphorus stoichiometry in two large non-stratified lakes and the impact on phytoplankton

The post-soviet period in Eastern Europe brought about fast changes in economy, land use, and environmental protection, whereas legacy effects of the previous era of heavy contamination continued emerging in the status of water bodies. In this paper, we analysed the post-soviet (since 1992) changes in catchment nutrient loadings and stoichiometry of nitrogen (N) and phosphorus (P) in two large non-stratified lakes in Estonia – Võrtsjärv and Peipsi. The drastic reduction in the application of P-fertilisers and P discharges with wastewaters since the early 1990s reduced P loadings and increased N/P loading ratio into both lakes. However, it was hard to find clear evidence of reduced in-lake nutrient concentrations and improved water quality. In both lakes, water transparency constantly decreased and phytoplankton biomass increased. Over the years, the difference in N/P ratio between the two lakes became smaller while the large differences in the cyanobacterial community composition remained. Although common thresholds in nutrient ratios favouring N2-fixing species could be revealed in both lakes, the phytoplankton in Võrtsjärv, strongly dominated by Limnothrix spp., remained mostly light-limited and the relationship with N/P stoichiometry was indirect. Random Forest analysis indicated an important role of light limitation in both lakes. Constantly lower levels of N in the deeper Lake Peipsi favoured N2-fixing species, which, as a paradox, became P-limited. As climate warming reinforces eutrophication phenomena in lakes by increasing internal nutrient loading and favouring bloom-forming cyanobacteria, more stringent measures would be needed to further limit nutrient loads (especially that of P) to lakes through improved wastewater treatment and increased efficiency of fertiliser application.Main financial support for EMU: European Union’s Horizon 2020 research and innovation programme Under the Marie Skłodowska-Curie Action, Innovative Training Networks, European Joint Doctorates.Project name, acronym and grant number: Management of climatic extreme events in lakes and reservoirs for the protection of ecosystem services, MANTEL, grant agreement No 722518.Publication date and, if applicable, length of embargo period: 20.11.2020, no embargo period

Nitrogen in Estonian lakes – the trends and impacts on Cyanobacteria

• The relative role of N&P to control eutrophication in lakes is continuously debated (Schindler et al. 2008). • Estonian limnologists have been P-believers as the post-socialist sharp reduction of N loading brought back cyanobacterial blooms in Lake Peipsi (Nõges et al. 2005) • The long debate has not discredited the importance of P-Control, but displayed evidence on the significance of N reduction to recover lake ecosystems (Paerl et al. 2016) • Chemically reduced N forms, such as NH4 + and urea favour non-N-fixing cyanobacteria (McCarthy et al. 2009)This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. Eesti Teadusagentuur / Estonian Research Council PRG 709, PRG 1167. Horizon 2020, European Union Funding fof Research & Innovation. Twinning CSA 951963.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. Eesti Teadusagentuur / Estonian Research Council PRG 709, PRG 1167. Horizon 2020, European Union Funding fof Research & Innovation. Twinning CSA 951963

Catchment land cover and soil as predictors of organic carbon, nitrogen, and phosphorus levels in temperate lakes : [presentation]

The presentation took place at the 10th International Conference on Shallow Lakes in 2021.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This study was funded by the Estonian Research Council grants PUTJD954, PRG705, and PRG709, and by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”. The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This study was funded by the Estonian Research Council grants PUTJD954, PRG705, and PRG709, and by the European Regional Development Fund through Estonian University of Life Sciences ASTRA project “Value-chain based bio-economy”. The Estonian Ministry of Environment and the Estonian Environment Agency supported data collection in the national monitoring program

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

Phytoplankton responses to meteorological and hydrological forcing at decadal to seasonal time scales

One of the challenges for predicting global change effects on aquatic ecosystems is the vague understanding of the mechanisms of multiple controlling factors affecting phytoplankton dynamics at different time scales. Here we distinguish between hydrometeorological forcing of phytoplankton dynamics at time scales from days to decades based on a 54-year monthly phytoplankton time series from a large shallow Lake Võrtsjärv (58 160N, 26 020E) in Estonia, combined with daily data on forcing factors— thermal-, wind-, light- and water-level regimes. By using variance partitioning with linear mixed effect modelling (LME), we found a continuum from the large dominant K-selected filamentous cyanobacteria with strongest decadal scale variation (8–30%) to r-selected phytoflagellates with large stochastic variability (80–96%). External forcing revealed strong seasonal variation (up to 80%), while specifically water level and wind speed had a robust decadal variation (8% and 20%, respectively). The effect of external variables was proportionally manifested in the time scales of phytoplankton variation. Temperature, with a clear seasonal variation, had no impact on the dominant cold tolerant filamentous cyanobacteria in Lake Võrtsjärv. We found the LME as a reliable method for resolving the temporal cross-scale problem. It yielded quantitative results that matched our intuitive understanding of the dynamics of different variables.Supplementary Information The online version of this article (https://doi.org/10.1007/s10750-021-04594-x) contains supplementary material, which is available to authorised users.This study was funded by MANTEL ITN (Management of climatic extreme events in lakes and reservoirs for the protection of ecosystem services) through European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 722518 and by the Estonian Research Council grants (PRG1266 and PRG1167). We would also like to thank Estonian Environment Agency for the long-term data used on this study.This study was funded by MANTEL ITN (Management of climatic extreme events in lakes and reservoirs for the protection of ecosystem services) through European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 722518 and by the Estonian Research Council grants (PRG1266 and PRG1167). We would also like to thank Estonian Environment Agency for the long-term data used on this study

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

Kas mäletad kevadet õites

http://www.ester.ee/record=b4485136*es

Mittetulirelva kasutamine hädakaitseks

http://www.ester.ee/record=b4406644~S58*es

Talundite pärimisõiguse reform

Digiteeritud Euroopa Regionaalarengu Fondi rahastusel, projekti "Eesti teadus- ja õppekirjandus" (2014-2020.12.03.21-0848) raames.https://www.ester.ee/record=b1143875*es

Lähedaste retseptor-anioon seondumisafiinsuste eristamine TMR meetodil

Käesolevas töös mõõdeti sorbaadi, heksanoaadi ja naprokseeni aniooni seondumisafiinsused (logKass) 23 uurea, indooli, karbasooli ja indolokarbasooli fragmentidel põhinevatele sünteetilistele retseptoritele. Kokku määrati 69 absoluutset seondumiskonstanti. Igale anioonile koostati kooskõlalised seondumisskaalad, mis kombineeriti tuumamagnetresonants (TMR) spektromeetrilise tiitrimise teel mõõdetud suhtelistest seondumiskonstandidest (ΔlogKass) ja UV-Vis spektrofotomeetrilisel või TMR spektromeetrilisel tiitrimisel saadud absoluutsetest seondumiskonstandidest. Saadud tulemused näitavad väga head kooskõla erinevate ΔlogKass mõõtmiste vahel, mis on saavutatud tänu TMR meetodi väga kõrgele täpsusele. Seetõttu on käesolevas töös võimalik eristada seondumisafiinsusi, mis erinevad teineteisest vaid 0,05 logKass ühiku võrra