Sirvi Autor "Tammeorg, Olga" järgi

Nüüd näidatakse 1 - 10 10

Cross border cooperation on environmental monitoring of Lake Peipsi: main results and perspectives : [presentation]
(Estonian University of Life Sciences, 2021) Tuvikene, Lea; Tammeorg, Olga; Nõges, Peeter; Nõges, Tiina
The presentation took place at the Lahti Lakes 2021 Symposium.
Effects of natural and anthropogenic pressures on variations in the water quality of large lakes
(Eesti Maaülikool, 2014) Tammeorg, Olga; Möls, Tõnu (advisor); Kangur, Külli (advisor)
An understanding of the factors that drive the water quality of large lakes is critical to the protection of such waterbodies. In the present study, the contributions made by riverine nutrient loading, sediment resuspension and weather factors to the water quality of large shallow Lake Peipsi were ascertained. High P concentration has been thought to be the main reason for the degradation of the water quality in this lake. It has hitherto been assumed that large shallow lakes are particularly influenced by sediment resuspension. However, there has been a lack of empirical studies that show this, because of the complexity of taking field-measurements. The in-field measurements of sediment resuspension taken for this study are the first ever to carried out in Lake Peipsi. Consequently, these data contribute to the overall knowledge on the unique ecosystems of large and shallow lakes. The Enonselkä basin of the large and shallow Lake Vesijärvi had been suffering from eutrophication, but the lake was successfully restored in the 1990s by reducing the external nutrient loading and also by efficiently removing fish. Since then however, signs of a recurrence in the deterioration of the water quality triggered further investigations of the gross sedimentation and sediment resuspension activities in that lake. The core findings of the studies carried out for this thesis are listed below. 1) Only a small decrease in P loading from the Estonian part of the catchment followed the dramatic reductions in the use of fertilizers, the downturn in livestock production and the improvement in wastewater treatment. Moreover, no significant long-term changes in TP concentrations in Lake Peipsi s.s. occurred, specifically since the 1990s. The annual in-lake TP concentrations were insensitive to the changes in TP loading through the major inflow. The hysteresis in the P dynamics of Lake Peipsi can be due to high P levels in its catchment soils, unchanged external loading from shared parts of its catchment, to internal P loading, and from changes in weather. 2) Sediment resuspension constituted the majority of the gross sedimentation in both Lake Peipsi and in Enonselkä. The spatial differences of the sediment resuspension were determined by the lake’s morphometry. Resuspension-mediated internal loading of TP dominated over the external loading in Lake Peipsi. Therefore, the present study provided the first empirical evidence for the high potential for recycling of P, which was originally brought into the lake by external loading. Sediment resuspension controlled the water quality through its significant influence on the loading of SS, turbidity, the concentrations of TP, and Chl a. Moreover, the results obtained from Enonselkä indicated that sediment fluxes from the shallow areas may govern the water quality of that whole lake. Resuspension, particularly in the shallow areas, triggered the internal loading of SS, which resulted in high water turbidity in the Enonselkä basin. This may be associated with the signs of recurring deterioration of the ecosystem exhibited since the late 1990s following the successful restoration in the 1990s. Macrophyte-based management of the shallow areas could contribute to the restoration of the whole basin. 3) The study of the long-term series of TP measurements revealed the significant contributions to the TP anomalies made by water temperature, water level, photosynthetically active radiation and wind speed. The variability of all these weather factors causes unexpected temporal and geographical deviations of the TP dynamics. Our quantitative estimations of the impacts of different weather variables on TP will help to predict changes in the water quality under different scenarios of climate change. Highly anomalous wind events were the main cause for TP changes. Extensive resuspension measurements in Lake Peipsi demonstrated that the wind affected TP concentration in the water column through the mechanism of sediment resuspension. As a higher frequency of extreme wind events can be expected in the future due to the climate change, severe implications on the lake ecosystems may follow due to the increase of internal P loading.
Factors behind the variability of phosphorus accumulation in Finnish lakes
(Springer, 2018) Tammeorg, Olga; Haldna, Marina; Nõges, Peeter; Appleby, Peter; Möls, Tõnu; Niemistö, Juha; Tammeorg, Priit; Horppila, Jukka; Centre for Limnology
Purpose Phosphorus retention (TPacc) is one of the major water quality regulators in lakes. The current study aimed at ascer- taining the specific lake characteristics regulating TP acc . Moreover, we were interested whether NAO (North Atlantic Oscillation), a proxy of climatic forcing, can explain variability in TPacc, additionally to that ascribed to lake characteristics. Materials and methods Sediment cores were obtained from 21 Finnish lakes, subject to radiometric dating and measurements of TP concentrations. Principal components (PCs) were generated using lake characteristics that are usually included into the modelling of TPacc (e.g. lake area, lake depth, catchment area, P inflow) but also the parameters that the classical models usually missed (e.g. anoxic factor). We used significant principal components (PCs), specific combinations of lake characteristics and monthly NAO values as predictors of TPacc. Results and discussion Lake characteristics explained the bulk of TPacc variability. The most influential factors (positive drivers) behind TPacc included PC1 (representing mainly deep lakes), PC2 (small lakes with high levels of anoxia and water column stability), PC3 (productive lakes with large catchment area and short water residence time), PC4 (lakes with high water column stability, low anoxic factor and relatively high sediment focusing) and PC5 (lakes with high levels of P inflow, anoxia and long water residence time). Additionally, we found a potential negative effect of NAO in October on the annual TPacc. This NAO was significantly positively related to temperatures in surface and near-bottom water layer (also their difference) in autumn, suggest- ing the possible implications for the internal P dynamics. Increased mineralization of organic matter is the most likely explanation for the reduced TPacc associated with NAO-driven water temperature increase. Conclusions The analysis presented here contributes to the knowledge of the factors controlling P retention. Moreover, this spatially and temporally comprehensive sediment data can potentially be a valuable source for modelling climate change implications.
Jätkusuutliku väikejärve tervendamise juhised
(Eesti Maaülikool, 2022) Tammeorg, Olga; Eesti Maaülikool. Põllumajandus- ja keskkonnainstituut. Hüdrobioloogia ja kalanduse õppetool
Inimtegevuse tagajärjel rikastuvad veekogud toiteainetega, mis toob endaga kaasa primaarproduktsiooni tõusu ning vee kvaliteedi halvenemise. Eutrofeerunud järvede vee kvaliteedi parandamine on praegusel ajal veekaitse üks peamisi ülesandeid kogu maailmas. Järvede tervendamine on kriitilise tähtsusega veeressursi säästliku majandamise seisukohalt. Tervendamiseks peetakse tegevust, mille tagajärjel saab veekogu hea seisundi. Seda eristatakse tavaliselt taastamisest (põhjalik järvesängi muutmine), korrastamisest (välisilme muutmine, mis ei pruugi parandada vee kvaliteeti), rehabiliteerimisest (Ott ja Timm, 2020). Järvi on vaja tervendada ka selleks, et vastata kehtivate veekaitseliste regulatsioonide (nt EL Veepoliitika raamdirektiiv) nõuetele. Värskeimate, 2020. a., andmete põhjal pole ligi 78% seirega kaetud Eesti seisuveekogumitest heas seisundis (Keskkonnaagentuur, 2021). Eriti murettekitav on aastail 2012-2020 jälgitav tendents, mille järgi heast kehvemas seisundis olevate järvede osakaalu on koguni suurenenud. Säärane statistika rõhutab vajadust üle vaadata seniseid järvede tervendamise praktikaid. Käesolevas töös pakutakse võimaliku lahendusena tervendamist jätkusuutlikul moel. Käesolevad juhised on välja töötatud 2020. a. augustis KIK toel valminud projekti „Jätkusuutlik väikejärve tervendamine sette eemaldamise ja selle toiteainete taaskasutuse teel“ jätkuprojekti raames. Meetodid on suunatud peamiselt väikejärvede tervendamiseks ning on toeks veemajandajatele.
Opportunities for combining data of Estonian and Russian monitoring to reflect on water quality in large transboundary Lake Peipsi
(Elsevier, 2022) Tammeorg, Olga; Tuvikene, Lea; Kondratyev, Sergey; Golosov, Sergey; Zverev, Ilya; Zadonskaya, Olga; Nõges, Peeter
Lake Peipsi, one of the world’s largest lakes, is shared between Estonia and Russia. The water quality in different parts of the lake has so far been assessed independently. Here we explore opportunities for combining data of Estonian and Russian monitoring. For that, we 1) analysed the compatibility of data for some water quality variables; 2) estimated the potential effects of the differences in sampling frequency; 3) provided a few regression models to calculate the missing data for months not sampled by the Russian side. Data of the concurrent Estonian and Russian sampling indicated a good compatibility. Estonian data analysis suggested that water quality assessment results are sensitive to sampling frequency. For example, total phosphorus (TP) in the largest basin showed a long-term decreasing trend in three month data that disappeared when data for other months were added. Disregarding some months may lead to underor overestimation of certain factors with no consistency in the response of different basins. Hence, data of the whole ice-free period are recommended for an adequate water quality assessment. Furthermore, we demonstrated that monthly values of the water quality variables of the same year are autocorrelated. Based on this, we filled the gaps in the long-term data and compiled a dataset for the whole lake that enables its most comprehensive use in water quality assessment and management. Long-term data revealed no water quality improvement of Lake Peipsi. Further reduction of the external nutrient load is needed. Eutrophication is sustained by high internal phosphorus load.
Phosphorus in Estonian soils, surface waters and lake sediments : [presentation]
(Estonian University of Life Sciences, 2023) Nõges, Peeter; Kisand, Anu; Kull, Anne; Ott, Ingmar; Tammeorg, Olga; Tõnno, Ilmar; Vilbaste, Sirje
Presentation at the 11th International Shallow Lakes Conference, Estonia 11.-16.06.2023.
Scientists’ Warning to Humanity: Rapid degradation of the world’s large lakes
(Elsevier, 2020) Jenny, Jean-Philippe; Anneville, Orlane; Arnaud, Fabien; Baulaz, Yoann; Bouffard, Damien; Domaizon, Isabelle; Bocaniov, Serghei A.; Chevre, Nathalie; Dittrich, Maria; Dorioz, Jean-Marcel; Dunlop, Erin S.; Dur, Gael; Guillard, Jean; Guinaldo, Thibault; Jacquet, Stephan; Jamoneau, Aurelien; Jawed, Zobia; Jeppesen, Erik; Krantzberg, Gail; Lenters, John; Leoni, Barbara; Meybeck, Michel; Nava, Veronica; Nõges, Tiina; Nõges, Peeter; Patelli, Martina; Pebbles, Victoria; Perga, Marie-Elodie; Rasconi, Serena; Ruetz, Carl R., III; Rudstam, Lars; Salmaso, Nico; Sapna, Sharma; Straile, Dietmar; Tammeorg, Olga; Twiss, Michael R.; Uzarski, Donald G.; Ventela, Anne-Mari; Vincent, Warwick F.; Wilhelm, Steven W.; Wangberg, Sten-Ake; Weyhenmeyer, Gesa A.; Centre for Limnology. Institute of Agricultural and Environmental Sciences
Large lakes of the world are habitats for diverse species, including endemic taxa, and are valuable resources that provide humanity with many ecosystem services. They are also sentinels of global and local change, and recent studies in limnology and paleolimnology have demonstrated disturbing evidence of their collective degradation in terms of depletion of resources (water and food), rapid warming and loss of ice, destruction of habitats and ecosystems, loss of species, and accelerating pollution. Large lakes are particularly exposed to anthropogenic and climatic stressors. The Second Warning to Humanity pro- vides a framework to assess the dangers now threatening the world’s large lake ecosystems and to eval- uate pathways of sustainable development that are more respectful of their ongoing provision of services. Here we review current and emerging threats to the large lakes of the world, including iconic examples of lake management failures and successes, from which we identify priorities and approaches for future conservation efforts. The review underscores the extent of lake resource degradation, which is a result of cumulative perturbation through time by long-term human impacts combined with other emerging stressors. Decades of degradation of large lakes have resulted in major challenges for restoration and management and a legacy of ecological and economic costs for future generations. Large lakes will require more intense conservation efforts in a warmer, increasingly populated world to achieve sustain- able, high-quality waters. This Warning to Humanity is also an opportunity to highlight the value of a long-term lake observatory network to monitor and report on environmental changes in large lake ecosystems.
Sediment phosphorus mobility in Võrtsjärv, a large shallow lake: Insights from phosphorus sorption experiments and long-term monitoring
(Elsevier, 2022) Tammeorg, Olga; Nürnberg, Gertrud K.; Tõnno, Ilmar; Kisand, Anu; Tuvikene, Lea; Nõges, Tiina; Nõges, Peeter
Sediment phosphorus (P) recycling is one of the key issues in lake water quality management. We studied sediment P mobility in Võrtsjärv, a large shallow lake in Estonia using both sorption experiments and long-term (1985–2020) monitoring data of the lake. Over the years studied, the lake has undergone a decline in external phosphorus loading (EL), while no improvement in phytoplankton indicators was observed. The results of the sorption experiments revealed that it may be successfully used as a tool to determine P forms involved in P retention, as up to 100%of the P fromthe water column was detected in sediments. Incubation of wet sediment is preferred to dry because of the sensitivity of organic P to desiccation. In the sediments of Võrtsjärv, the labile P (Lab-P) and iron bound (Fe-P) fractions are the major forms of the mobile pool that supply internal P load as sediment released P. The internal P load calculated from summer total P (TP) increases (ILin situ) in the water column was on average 42%, but could reach 240% of EL at extreme environmental conditions. ILin situ was correlated with the active area, which resembles the area involved in redox-related P release in polymictic lakes, and with the mean bottom shear stress in summer. ILin situ showed a similar decreasing pattern as the external P load over the years 1985–2020, and was likely driven by the decrease of the pool of releasable P. Similarly, the decreases in sediment loading by P retention in our P sorption experiment were associated with decreases in the concentration of the potentially mobile P forms (mainly Lab-P and Fe-P). These results show that changes in external P loading can successfully control internal P loading and are useful in water quality management of large lakes.
Spatio-temporal variations in sediment phosphorus dynamics in a large shallow lake: Mechanisms and impacts of redox-related internal phosphorus loading
(Elsevier, 2023) Tammeorg, Olga; Nürnberg, Gertrud K.; Tõnno, Ilmar; Toom, Lauri; Nõges, Peeter
The role of redox-related sediment phosphorus (P) release in shallow polymictic lakes remains poorly understood. Our previous studies in large and shallow Lake Peipsi suggested the importance of the redox-related P release in internal P loading. In the current study, we explored the validity of this hypothesis by also considering organic sediment P (Org-P). We analysed spatio-temporal changes in diffusive P flux and sediment P forms determined by P fractionation and nuclear magnetic resonance (NMR) spectroscopy in summer 2021. Using 1997–2021 data, we computed internal P load (IL) by two methods and studied their relationships with several water quality variables. Anoxia of sediment surfaces and P release progressed with an increase in water tem- perature during summer. In the long-term, IL estimates by two methods were similar (mean values: 315 and 346 mg/m2/year) and correlated with the predicted anoxia of sediment surfaces (AApred). A contribution of sediment iron-bound P (Fe-P) to P release was indicated by the positive correlation of Fe-P with orthophosphate (NMR) in the short-term studies. No similar evidence was found for Org-P, which contradicts the common tendency to attribute internal P loads largely to Org-P in eutrophic lakes. Nevertheless, organic matter seemed to support reductive dissolution, because seasonal changes in sediment Org-P correlated with those in Fe-P, and organic matter content and diffusive P flux were negatively correlated over different sites. Complex bottom morphology and hydrology affected spatial distribution of the sediment P forms and masked the relationships between sediment P variables and P release. Finally, the importance of redox-related release was reflected in significant relationships between AApred and associated IL with Secchi depth transparency, chlorophyll a concentration, and the biomass of phytoplankton and cyanobacteria. To our knowledge, this is the first time when such direct ev- idence was provided for a large polymictic lake.
Sustainable lake restoration: From challenges to solutions
(Wiley, 2023) Tammeorg, Olga; Chorus, Ingrid; Spears, Bryan; Nõges, Peeter; Nürnberg, Gertrud K.; Tammeorg, Priit; Søndergaard, Martin; Jeppesen, Erik; Paerl, Hans; Huser, Brian; Horppila, Jukka; Jilbert, Tom; Budzyńska, Agnieszka; Dondajewska-Pielka, Renata; Gołdyn, Ryszard; Haasler, Sina; Hellsten, Seppo; Härkönen, Laura H.; Kiani, Mina; Kozak, Anna; Kotamäki, Niina; Kowalczewska-Madura, Katarzyna; Newell, Silvia; Nurminen, Leena; Nõges, Tiina; Reitzel, Kasper; Rosińska, Joanna; Ruuhijärvi, Jukka; Silvonen, Soila; Skov, Christian; Važić, Tamara; Ventelä, Anne-Mari; Waajen, Guido; Lürling, Miquel
Sustainable management of lakes requires us to overcome ecological, economic, and social challenges. These challenges can be addressed by focus- ing on achieving ecological improvement within a multifaceted, co-beneficial context. In-lake restoration measures may promote more rapid ecosystem responses than is feasible with catchment measures alone, even if multiple interventions are needed. In particular, we identify restoration methods that support the overarching societal target of a circular economy through the use of nutrients, sediments, or biomass that are removed from a lake, in agricul- ture, as food, or for biogas production. In this emerging field of sustainable restoration techniques, we show examples, discuss benefits and pitfalls, and flag areas for further research and development. Each lake should be assessed individually to ensure that restoration approaches will effectively address lake-specific problems, do not harm the target lake or downstream ecosystems, are cost-effective, promote delivery of valuable ecosystem ser- vices, minimize conflicts in public interests, and eliminate the necessity for repeated interventions. Achieving optimal, sustainable results from lake res- toration relies on multidisciplinary research and close interactions between environmental, social, political, and economic sectors.

Sirvi Autor "Tammeorg, Olga" järgi

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