16th International Living Lakes Conference, Puno, Peru, December 16-18, 2022

EU Horizon 2020 Project „Towards Research Excellence and Innovation Capacity in Studying Lake Ecosystems’ Functional Structures and Climate Change Impact“ – TREICLAKE – aims to increase the scientific expertise of Estonian lake researchers to achieve larger impact not only in science but also in society at large.We tighten co-operation with two European high-level universities – University of Jyväskylä, Finland and Aarhus University, Denmark, to: • learn the newest scientific methodologies • publish high-level scientific articles and enable Open Access to them • better ivolve graduate students and early-stage researchers • increase our contribution to the formation of lake management policies • raise society's awareness of the necessity and possibilities of maintaining and improving the ecological condition of lakes.What is the use of lake science in the management and maintenance of lakes? Lea Tuvikene 16th International Living Lakes Conference, Puno, Peru, December 16-18, 2022 EU Horizon 2020 Project „Towards Research Excellence and Innovation Capacity in Studying Lake Ecosystems’ Functional Structures and Climate Change Impact“ – TREICLAKE – aims to increase the scientific expertise of Estonian lake researchers to achieve larger impact not only in science but also in society at large. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 951963. This work was supported by the Estonian Research Council grant PRG709

SDSS surface photometry of M 31 with absorption corrections

The objective of this work is to obtain an extinction-corrected distribution of optical surface brightness and colour indices of the large nearby galaxy M 31 using homogeneous observational data and a model for intrinsic extinction. We process the Sloan Digital Sky Survey (SDSS) images in ugriz passbands and construct corresponding mosaic images, taking special care of subtracting the varying sky background. We apply the galactic model developed in Tempel et al. (2010) and far-infrared imaging to correct the photometry for intrinsic dust effects. We obtain observed and dust-corrected distributions of the surface brightness of M 31 and a map of line-of-sight extinctions inside the galaxy. Our extinction model suggests that either M 31 is intrinsically non-symmetric along the minor axis or the dust properties differ from those of the Milky Way. Assuming the latter case, we present the surface brightness distributions and integral photometry for the Sloan filters as well as the standard UBVRI system. We find the following intrinsic integral colour indices for M 31: (U-B)_0=0.35; (B-V)_0=0.86; (V-R)_0=0.63; (R-I)_0=0.53; the total intrinsic absorption-corrected luminosities of M 31 in the B and the V filters are 4.10 and 3.24 mag, respectively.Comment: 6 pages, 8 figures, accepted for publication in A&A. The high-resolution zoomable colour image of M 31 can be seen at http://www.aai.ee/~elmo/m31

Loodusliku muutlikkuse mõju madalate järvede ökoseisundi hindamisele

A thesis for applying for the degree of Doctor of Philosophy in Applied BiologyThe dissertation contributes to the improvement of large lake monitoring, demonstrating that besides following the class boundaries of ecological status established by law, reliable status estimates of such lakes require profound expert knowledge on ecosystem functioning, and considering the share of natural and human induced factors influencing the ecosystem. WFD defines the status of water bodies by the extent of anthropogenic deviation from the reference conditions, i.e. conditions that should occur at sites of any particular type in the absence of human impact. Ecological status of Estonian large, shallow lakes Peipsi and Võrtsjärv is greatly influenced by direct human activities as well as climate change. For example, the trend of water brownification influencing the whole matter circulation of lakes, results from natural hydrological processes, but also from decreasing atmospheric sulphur deposition – both determining the mobility of humic substances. It is a complicated task to find simple, well-functioning indicators to assess ecological status of water bodies which are influenced by natural factors, such as large water level fluctuations and strong seasonality, more than by human impact. For example, for Lake Võrtsjärv, all common water quality indicators show worse ecological status in periods of low water level despite unchanged human impact. It should also be considered that the influence of changed environmental conditions may become evident with a time lag – after one or even several years. In Lake Võrtsjärv, changes in water surface temperature and water level explain approximately one half of the total changes in values of ecological status indicators. The reliability of status estimates can be significantly increased by statistically correcting the values of status indicators for factors causing natural variability. Analysis of spatial variability of status indicators in Lake Võrtsjärv showed that the permanent sampling station at the deepest site of the lake is representative for more than 90% of the lake area. To improve cost-effectiveness of the state monitoring programme, this sampling site remains the only open water monitoring site at the lake since 2017.Töö annab panuse suurte madalate järvede seire paremaks korraldamiseks, näidates, et usaldusväärse seisundihinnangu andmiseks on lisaks seadusega paika pandud veekvaliteedi klassipiiride järgimisele vaja ka põhjalikke teadmisi ökosüsteemi kui terviku talitlusest ja seda mõjutavatest teguritest. Vastavalt Euroopa Liidu veepoliitika raamdirektiivile tuleb looduslike veekogude seisundit ja selle muutusi hinnata lähtuvalt inimmõju ulatusest. Eesti suurte ja madalate järvede, Peipsi ja Võrtsjärve, seisundit mõjutavad tugevalt nii nende valglal toimuv otsene inimtegevus kui ka kliima ja selle muutused. Näiteks peituvad kogu järvede aineringet mõjutava vee „pruunistumise“ trendi taga nii looduslikud hüdroloogilised põhjused kui ka atmosfäärse väävlireostuse vähenemine, mis mõlemad mõjutavad huumusainete liikuvust. Selliste veeökosüsteemide seisundi hindamiseks, kus inimtegevuse mõjude kõrval on ülekaalus looduslikud tegurid nagu suured veetaseme kõikumised ja tugev sesoonsus, on raske leida lihtsaid, hästitoimivaid indikaatoreid. Näiteks Võrtsjärves näitavad kõik tavapärased veekvaliteedi mõõdikud madalvee perioodidel halvemat olukorda isegi muutumatu inimmõju tingimustes ja tihti on inimtekkeliste ja looduslike muutuste vahel raske vahet teha. Tuleb ka arvestada, et muutunud keskkonnatingimuste mõju võib avalduda hilinemisega – alles järgmisel aastal või isegi aastate pärast. Võrtsjärves selgitavad vee pinnatemperatuuri ja veetaseme muutused ligikaudu poole ökoseisundi näitajate kogumuutlikkusest. Seisundihinnangu usaldusväärsust saab oluliselt tõsta, kui seisundinäitajate väärusi statistiliste meetodite abil korrigeerida looduslikku muutlikkust põhjustavate tegurite suhtes. Võrtsjärve seisundinäitajate ruumilise muutlikkuse analüüs näitas, et järve sügavaimas kohas asuv seirekoht iseloomustab hästi järve kogu avaveelist osa ehk rohkem kui 90% tema pindalast. Kulude kokkuhoiu eesmärgil ongi see alates 2017. aastast riiklikus seireprogrammis ainuke avavee seirekoht.Publication of this thesis is supported by the Estonian University of Life Sciences

Growth and management of Silver birch and Hybrid aspen in southern Sweden

Nowadays, the changing climate and the risks associated with it urge us to re-evaluate our silvicultural practices. Due to the increasing demand for wood and good economy amongst other factors, Swedish forest landscape is dominated by two species – Norway spruce Picea abies (L.) Karst. and Scots pine Pinus sylvestris (L.) However, there are other species such as silver birch Betula pendula Roth and hybrid aspen Populus × wettsteinii Hämet-Ahti = P. tremula L. × P. tremuloides Michx. – two of the fast-growing tree species in Baltic sea region, including Sweden, that may complement the species composition in Sweden, providing various benefits, especially in the face of the changing climate. The main objective of the thesis was to evaluate the early growth of silver birch and hybrid aspen depending on the management done so far. Also, to assess the growth and economy of full rotation birch stands in southern Sweden using a standard management regime. Data was collected from four experimental sites located in southern Sweden established on both forest land and agricultural land. Different functions were applied to estimate both early growth, e.g. height, basal area, volume, as well as future growth and development of silver birch stands. A statistical model was constructed to test the effect of fertilization. Genetically improved silver birch (Ekebo 4) showed comparable growth next to hybrid aspen which is proved as one of the fast-growing tree species in Sweden. Statistical analysis revealed that fertilization has a significant effect on all growth parameters tested (height, DBH & volume) of both species, with differences between fertilized and unfertilized values being larger for hybrid aspen. Simulations of full rotation stands of silver birch showed that optimal rotation length of birch stands planted with improved material is between 36 – 40 years, while mean annual increment varies from 9.2 – 13.3 m3 ha-1 year-1 with the best performance delivered by birch planted on agricultural land

Variability survey of brightest stars in selected OB associations

The stellar evolution theory of massive stars remains uncalibrated with high-precision photometric observational data mainly due to a small number of luminous stars that are monitored from space. Automated all-sky surveys have revealed numerous variable stars but most of the luminous stars are often overexposed. Targeted campaigns can improve the time base of photometric data for those objects. The aim of this investigation is to study the variability of luminous stars at different timescales in young open clusters and OB associations. We monitored 22 open clusters and associations from 2011 to 2013 using a 0.25-m telescope. Variable stars were detected by comparing the overall light-curve scatter with measurement uncertainties. Variability was analysed by the light curve feature extraction tool FATS. Periods of pulsating stars were determined using the discrete Fourier transform code SigSpec. We then classified the variable stars based on their pulsation periods and available spectral information. We obtained light curves for more than 20000 sources of which 354 were found to be variable. Amongst them we find 80 eclipsing binaries, 31 $\alpha$ Cyg, 13 $\beta$ Cep, 62 Be, 16 slowly pulsating B, 7 Cepheid, 1 $\gamma$ Doradus, 3 Wolf-Rayet and 63 late-type variable stars. Up to 55% of these stars are potential new discoveries as they are not present in the Variable Star Index (VSX) database. We find the cluster membership fraction for variable stars to be 13% with an upper limit of 35%.Comment: 36 pages, 11 figures, catalogue in appendix

Improving administrative effectiveness of lake management in the frames of River Basin Management Plans : Implementation Plan

Fresh waters make only 3% of the global water resources. Freshwater lakes, including reservoirs and ponds, are important elements for communities and their relevance is increasing. Lake ecosystems and their catchments have provided several societally valuable benefits and ecosystem services like shelter, drinking water, bathing water, food, a means of travel and wealth in a number of ways and allowed whole cultures to develop. Lakes have values associated with well-being and relaxation, their proximity has catalyzed rural development and been important in the regional socio-economic development. Lake districts are often very popular destinations for domestic and foreign tourism and visitors. Eutrophication and its ecological consequences, pollution, over abstraction and invasive species are serious threats and increase the need for restoration and management to prevent the potential adverse economic and social impacts. There is increasing evidence that lakes are affected by climate change. Lake management is for these reasons an important part of sustainable regional development as set by Lisbon and Gothenburg agreements. However, the most significant piece of legislation in response to the increasing threat of pollution and the increasing demand from the public for cleaner lakes, rivers and beaches and freshwater biodiversity, is the EU Water Framework Directive (WFD). This Directive is unique in that it sets out an established framework for the protection of all water bodies (including lakes) and for all EU member states to achieve good water ecological status by December 2015. This objective is likely to be achieved in slightly over half (53 %) of EU waters (A blueprint…, 2013) and, therefore, more effort need to be scheduled for the following 6-year periods of WFD. The economic values of attractive, clean lakes are well established. There is a rising appreciation of good quality lakes across Europe. More intensive lake protection through sharing good practices with European lake managers and the regional influencing bodies is critical if we want to improve the current quality of lakes in Europe and to build long term capacity for sustainable use of lakes

Period change of massive binaries from combined photometric and spectroscopic data in Cygnus OB2

Context. Mass loss is an important property in evolution models of massive stars. As up to 90% of the massive stars have a visual or spectroscopic companion and many of them exhibit mass exchange, mass-loss rates can be acquired through the period study of massive binaries. Aims. Using our own photometric observations as well as archival data, we look for variations in orbital periods of seven massive eclipsing binary systems in the Cygnus OB2 association and estimate their mass-loss rates and stellar parameters. Methods. We use a Bayesian parameter estimation method to simultaneously fit the period and period change to all available data and a stellar modelling tool to model the binary parameters from photometric and radial-velocity data. Results. Four out of the seven selected binaries show non-zero period change values at two-sigma confidence level. We also report for the first time the eclipsing nature of a star MT059.Comment: 12 pages, 18 figures, accepted for publication in A&

Spiral arms and disc stability in the Andromeda galaxy

Aims: Density waves are often considered as the triggering mechanism of star formation in spiral galaxies. Our aim is to study relations between different star formation tracers (stellar UV and near-IR radiation and emission from HI, CO and cold dust) in the spiral arms of M31, to calculate stability conditions in the galaxy disc and to draw conclusions about possible star formation triggering mechanisms. Methods: We select fourteen spiral arm segments from the de-projected data maps and compare emission distributions along the cross sections of the segments in different datasets to each other, in order to detect spatial offsets between young stellar populations and the star forming medium. By using the disc stability condition as a function of perturbation wavelength and distance from the galaxy centre we calculate the effective disc stability parameters and the least stable wavelengths at different distances. For this we utilise a mass distribution model of M31 with four disc components (old and young stellar discs, cold and warm gaseous discs) embedded within the external potential of the bulge, the stellar halo and the dark matter halo. Each component is considered to have a realistic finite thickness. Results: No systematic offsets between the observed UV and CO/far-IR emission across the spiral segments are detected. The calculated effective stability parameter has a minimal value Q_{eff} ~ 1.8 at galactocentric distances 12 - 13 kpc. The least stable wavelengths are rather long, with the minimal values starting from ~ 3 kpc at distances R > 11 kpc. Conclusions: The classical density wave theory is not a realistic explanation for the spiral structure of M31. Instead, external causes should be considered, e.g. interactions with massive gas clouds or dwarf companions of M31.Comment: 12 pages, 8 figures, Astron & Astrophys accepte