Stone Burial Grounds to the East of Lake Peipsi: To the Statement of the Problem

В статье рассматриваются каменные могильники второй половины I - начала II тысячелетия, расположенные к востоку от Псковско-Чудского озера в зоне интенсивных культурных контактов между территориями российского Северо-Запада и Эстонии. Выделяется две группы памятников: на западной окраине Ижорского плато и в Псковско-Изборском регионе. Могильники Ижорского плато, аналогично каменным могильникам Северо-Восточной Эстонии, представляют собой так называемые могильники с оградками (таранды), сооруженные в римское время и использовавшиеся для захоронений в середине - третьей четверти I тысячелетия. Могильники Псковско-Изборского региона датируются эпохой викингов (за исключением могильника Выбуты) и представляют собой отдельное культурное явление. Каменные могильники обеих групп часто топографически связаны с позднейшими курганно-жальничными могильниками, в которых встречены аналогичные каменным могильникам кладки. Stone burials of second half of 1st - the beginning of 2nd millenium, located to the east from Lake Peipsi (Pskov-Chudskoe) in the zone of intensive cultural contacts between territories of the Russian North-West and Estonia are considered. Two groups of monuments are distinguished: on the western outskirts of Izhora Plateau and in Pskov-Izborsk region. Graves of Izhora plateau, similarly to stone burials of NorthEastern Estonia, are so called fenced burials (tarands), built in Roman time and used for burials in middle - third quarter of the 1st millennium. Graves of Pskov-Izborsk region date from the Viking Age (with the exception of Vybuty burial ground) and represent a separate cultural phenomenon. Stone burial grounds of both groups are often topographically connected with later barrow-zhalnik cemeteries, in which fences similar to stone burial grounds are found.

Lake Peipsi in the Pskov-Livonian Frontier System of the 15 - Early 16 Century

В статье рассматривается проблема размежевания русско-ливонского «фронтирного» пространства в районе Чудского озера. Основными претендентами на него были Псков и Дерпт, которые обладали примерно равным потенциалом. Ливонский орден, у которого не было флота, не мог оказать Дерпту прямую помощь, но как ландсгерр Ревеля, обладавшего сильным флотом, имел возможность заставить его оказать содействие. Это нарушало баланс сил в пользу Дерпта, поскольку потенциальные союзники Пскова, Новгород и Москва, флотом на Чудском озере не располагали. В борьбе за Чудское озеро Псков использовал заселение и хозяйственно-административное освоение чудских берегов. Чтобы помешать псковичам закрепиться в прибрежных районах, Ливонский орден в ходе войны 1480-1481 гг. производил их «зачистки», а также накапливал опыт мобилизации сил Дерпта, Ревеля и ордена для проведения боевых операций с использованием озерных флотилий. The article is concerned with the problem of delimiting the Russian-Livonian frontier space in the area of Lake Peipsi (Chudskoe). The main contenders for it were Pskov and Dorpat, who had approximately equal potential. The Livonian Order, which did not have a fleet, could not provide direct assistance to Dorpat, but as Landsherr of Reval, who possessed a strong fleet, it was able to force him to assist him. It upset the balance of power in favor of Dorpat, since the potential allies of Pskov, Novgorod and Moscow, did not have a fleet on Lake Peipsi. In the struggle for Lake Peipsi, Pskov used the settlement and economic and administrative development of the Peipsi shores. In order to prevent the Pskovians from gaining a foothold in the coastal areas, the Livonian Order during the war of 1480-1481 carried out their “clean-up”, and also gained experience in mobilizing the forces of Dorpat, Reval and the Order for conducting combat operations using lake flotillas.

Using the “mean temperature of the catch” to assess fish community responses to warming in a temperate lake

This contribution applies the “mean temperature of the catch” (MTC) concept of Cheung et al. (Nature 497:365–368, 2013) to fish catch data for Lake Peipsi, Estonia/Russia, covering the years 1931 to 2019. The preferred temperature of each of the ten target fish species was obtained from the literature, and combined with the species-specific catch data to obtain MTC values for each year. The analysis of the MTC time series thus obtained with a segmented regression yielded two trend lines, one horizontal at 14.5 °C (1931–1986), and the other (1987–2019) ascending with a slope 0.85 °C·decade−1. Overall, the segmented regression model explains over half of the variance of the MTC data set (multiple R2 = 0.53; adjusted R2 = 0.51). Lake surface water temperatures correlate with MTC, even though weakly (r = 0.30), when considering a 2-year time lag. The fish community of the shallow Lake Peipsi reacts more strongly to temperature changes than marine ecosystems so far studied using the MTC.

SEASONAL DYNAMICS OF PHYTOPLANKTON AND SOME HYDROCHEMICAL INDICATORS OF THE PEIPSI-PSKOV LAKE

The Peipsi-Pskov Lake is the largest freshwater body in Europe, ranking fourth in area and fifth in volume. It is characterized by shallow water and a high level of trophy. The water in the lake is poorly mineralized and has little transparency due to suspended sediments and the development of plankton. Phytoplankton acts as a primary link in trophic chains, quickly reacts to changes in the aquatic environment and serves as a convenient object in monitoring studies.The average concentrations of total nitrogen in the lake during the observation period were in the range of 525-818 µg/dm3. The content of ammonium, nitrate, and nitrite nitrogen in the samples was mostly below the detection limits. The values of total phosphorus varied from 20 µg/dm3 to 54 µg/dm3, and its concentrations were lower than the sensitivity of the method during the flood recession.The maximum values of total nitrogen and phosphorus were recorded in August: in Lake Peipsi - 1.12 mg/dm3 and 0.09 mg/dm3, in Lake Pskov - 1.59 mg/dm3 and 0.14 mg/dm3, respectively. BOD5 values ranged from 1.96 mg/dm3 in autumn to 4.26 mg/dm3 in summer.During the growing season of 2020, 244 species taxa of phytoplankton from 8 phylums were identified in the Peipsi-Pskov Lake: Chlorophyta, Bacillariophyta, Cyanobacteria, Chrysophyta, Euglenophyta, Cryptophyta, Dinophyta and Xanthophyta. Floristic complex was characterized as сhlorophyta-diatom-cyanobacterial.The number of phytoplankton varied between 2.1 and 16.2 million cells/l depending on the season. The average number was 7.6 million cells/l. The biomass values ranged from 0.9 g/m3 to 3.6 g/m3. The average biomass was 2.3 g/m3.According to the ecological and geographical characteristics of the lake, widespread freshwater forms of microalgae predominated, preferring stagnant-flowing, slightly alkaline waters.Saprobiological analysis showed that the waters of the Peipsi-Pskov Lake were classified as moderately polluted, class III of water purity quality.

How Did the Late 1980s Climate Regime Shift Affect Temperature-Sensitive Fish Population Dynamics: Case Study of Vendace (Coregonus albula) in a Large North-Temperate Lake

The population dynamics of fish in northern lakes is strongly influenced by climatic factors. In this study, we investigated whether there is a link between the late 1980s climate regime shift in Europe and the collapse of vendace (Coregonus albula) population at the same time in Lake Peipsi. Until the end of the 1980s, vendace was very abundant in the lake, but then its catches sharply declined. This decline inspired investigations into the extreme weather events preceding the vendace collapse using data on daily water temperatures and ice phenology together with commercial fishery statistics since 1931 and test catch data since 1986. We identified using advanced statistical methods that the hot summer of 1988, which was accompanied by a severe cyanobacterial bloom and extensive fish kill, and the subsequent non-permanent ice cover and early ice-offs in 1989 and 1990 in Lake Peipsi were the main reasons for the disappearance of vendace from catches in 1991. Moreover, a negative correlation appeared between catches of the predatory pikeperch (Sander lucioperca) and vendace. Predation pressure as well as fish habitat degradation caused by lake eutrophication may contribute to the instability of the vendace population too. Our study showed that extreme weather events such as heat waves in summer and non-permanent ice-cover in winter in consecutive years may have long-lasting harmful effects on the population abundance of cool-water fish species such as vendace whose eggs usually develop under an ice cover in north-temperate lakes.

Using Microcystin Gene Copies to Determine Potentially-Toxic Blooms, Example from a Shallow Eutrophic Lake Peipsi

Global warming, paired with eutrophication processes, is shifting phytoplankton communities towards the dominance of bloom-forming and potentially toxic cyanobacteria. The ecosystems of shallow lakes are especially vulnerable to these changes. Traditional monitoring via microscopy is not able to quantify the dynamics of toxin-producing cyanobacteria on a proper spatio-temporal scale. Molecular tools are highly sensitive and can be useful as an early warning tool for lake managers. We quantified the potential microcystin (MC) producers in Lake Peipsi using microscopy and quantitative polymerase chain reaction (qPCR) and analysed the relationship between the abundance of the mcyE genes, MC concentration, MC variants and toxin quota per mcyE gene. We also linked environmental factors to the cyanobacteria community composition. In Lake Peipsi, we found rather moderate MC concentrations, but microcystins and microcystin-producing cyanobacteria were widespread across the lake. Nitrate (NO3−) was a main driver behind the cyanobacterial community at the beginning of the growing season, while in late summer it was primarily associated with the soluble reactive phosphorus (SRP) concentration. A positive relationship was found between the MC quota per mcyE gene and water temperature. The most abundant variant—MC-RR—was associated with MC quota per mcyE gene, while other MC variants did not show any significant impact.

Expeditionary Journals of Major General G. N. Karaev, Leader of the Combined Expedition to Establish the Exact Location of the Battle on the Ice: The Second Half of the 1950s — Early 1960s

Recent studies of the Battle of the Ice (1242) in many respects derive from the late 1950s–early 1960s expedition of the Academy of Sciences of the USSR to the region of Lake Peipsi that was to determine the battle location. The reliability of the results it obtained is now evaluated differently, especially by those zealously searching for evidence of state commission. Materials collected and research carried out and published as early as 1962 is now used in disputes; however the authors contend that that they are not sufficient for making balanced and objective conclusions. Handwritten diaries of the expedition leader G. N. Karaev should shed a new light on the history of the project: its preparation, field work progress, and applied methods. The diaries covering the period of 1956-1960 are stored in the fonds of the Archive of the Pskov State United Historical, Architectural, and Fine Arts Museum-Reserve. The text refers directly to the time of the described events (to a day). The diaries expound the research process (including submarine studies) and the general mood of the expedition. They show that the initiative came from the local historians, some of those amateurs. However, support of the leading scholars (particularly, academician M.N. Tikhomirov) and of the USSR Academy of Sciences gave the project its scientific force. The documents attached to the diaries confirm that G. N. Karayev founded his conclusions on the changes in level and depths of the lake, its bottom relief, and reasons for the absence of finds that definitely dated from the 13thcentury on the data obtained by experts in the natural and exact sciences. The authors conclude that the expedition journals of G. N. Karaev confirm the reliability of its results.

Modeling point and non-point nutrient fluxes in river systems of lake Peipsi drainage basi

N and P compounds work as key elements causing bioproduction and eutrophication inwater bodies of the Baltic Sea region, A large-scale dynamic GIS-embedded PolFlowmodel considers all point and diffuse emission sources in a river basin simulating alsotransport and retention of nutrients in time steps of five years, This modeling approachwas originally developed for simulating past and present nutrient loads for the Rhine andElbe rivers. In addition, a statistical model MESAW was employed for nutrient sourceapportionment and emission estimations. This paper analysis the modeling results in LakePeipsi basin, shared by Estonia, Russia and Latvia, for long-term trends since 1985 till1999. Results of modeling, as well as monitoring data indicate quite stable long-term Pload while agricultural N load has decreased significantly in connection with dramaticchanges in agricultural structures. That, in turn, has lead to sharp decrease ofN/P ratio inriverine runoff while in lakes (L Peipsi, L Vortsjii.rv) and coastal seas, NIP ratio hasdropped below 10. These changes, enhancing cyanobacterial blooms, have significantlyworsened the ecological state of these water bodies, in the conditions of decreasedemissions. The paper concludes that wastewater treatment should focus on better removalofphosphorus.