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Environmental Variables Significance for Ecological Status Assessment in the Bulgarian Eastern Continental Shallow Lakes

Doychev Dimitar, Gartsiyanova Kristina, Taneva Lidiya

Journal of Ecological Engineering

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2024

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Vol. 25, nr 10

16--30

EN

Eastern Continental shallow lakes are specific with their higher nutrient concentration compared to other lentic water bodies with similar specifications. Nonetheless, their phytoplankton and macrophyte assessment systems used more often than others within state monitoring programs, are weakly influenced by nutrient concentrations, unlike all other lake types in Europe. In this study, we used all available data for Eastern Continental shallow lakes on the Black Sea coast of Bulgaria from the state monitoring for 14 years (2008–2021). The goal was to find how environmental variables influence the ecological status assessment by phytoplankton and macrophyte-related indices. Likewise, it was important to understand the studied parameter’s interrelations within Dourankoulak Lake and the lake complex Shabla-Ezerets. The most important environmental parameters were determined with principal component analysis since it helps find the hidden relationships. Afterwards, those variables were used for univariate linear regression testing because of its simplicity and reliability. The aim was to find the best-suited parameters for the ecological status explanation by different biological indices, which can be used for further predictions of the ecosystem condition. In addition, nitrogen–phosphorus dependency, where possible was investigated, confirming conclusions from mesocosms studies from water bodies with similar characteristics. The algae group index or the so-called “Catalán Index”, in its original form of representing results and considering its ecological quality ratio values, was influenced by conductivity concentrations the most in Ezeretsko Lake and weaker at Dourankoulak Lake. Nutrient relationship with biological quality elements was not found, confirming results on a European level. In Shablensko Lake a dose-dependent relation between nitrates and phosphates was found, which shows that augmenting the quantity of nitrogen is related to the increasing concentration of phosphates.

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The lower reaches of the Nemunas River at the end of the Last (Weichselian) Glacial and beginning of the Holocene

Bitinas A., Druzhinina O., Damušytė A., Napreenko-Dorokhova T., Guobytė R., Mažeika J.

Geological Quarterly

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2017

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Vol. 61, No. 1

156--165

EN

The Russian–Lithuanian cross-border area around the Nemunas and Šešupė rivers confluence is a key area for solving palaeogeographic issues important for this region: when the Nemunas Delta started to form, why the essential changes of hydrographic network occurred, and so on. The results of conventional radiocarbon (14C) dating and pollen analysis in the present dry valley between the Šešupė River and the Įrutis River as well as the results of former studies at the Riadino-5 archaeological site suggest that the essential changes in the Nemunas River hydrographic system occurred before 9.5 ka, most likely in Preboreal time, when the Nemunas River cut through the Vilkiškė Marginal Ridge and started to flow directly to the west from this ridge into one of the former basins of the Baltic Sea – to the Yoldia Sea, or to the Ancylus Lake. A new divide was formed between the Šešupė and Įsrutis rivers, and the basins of the Nemunas and Prieglius rivers (formerly a single hydrographic system) became two independent drainage basins of the Baltic Sea. The present Nemunas Delta formation started after the Litorina Sea transgression when the Nemunas River mouth moved from a Baltic Sea nearshore position to close to the western margin of the Vilkiškės Marginal Ridge. A set of palaeogeographic reconstructions of the Nemunas and Šešupė rivers confluence area for different periods of the very end of the Last (Weichselian) Glacial and the beginning of the Holocene have been constructed.

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Evolution of Arkona Basin environment in the Holocene in the light of diatom research

Janczak-Kostecka B.

Landform Analysis

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2015

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Vol. 29

19--25

EN

This article presents the results of diatom studies from three cores taken from the Arkona Basin. The main stages of the Baltic Sea evolution in the Holocene – Ancylus Lake, Mastogloia Sea, Littorina Sea, and Post-Littorina Sea – were identified in diatom assemblages. The transition stage between Ancylus Lake and Littorina Sea, called Mastogloia Sea, was not such a long period as in the Mecklenburg Bay but was essential in the evolution of the Baltic Sea. The most pronounced feature of this period was an increase in the number of halophilous species, which reflected the existence of the littoral environment at the onset of this stage. The appearance and development of halophilous species was stimulated by stepwise inflows of saline waters. The composition of diatom assemblages reflected natural eutrophication of the Baltic Sea during the Littorina Sea stage.

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Age and evolution of the Littorina Sea in the light of geochemical analysis and radiocarbon dating sediment of cores from the Arkona Basin and Mecklenburg Bay (SW Baltic Sea)

Kostecki R.

Landform Analysis

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2015

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Vol. 29

27--33

EN

Two sediment cores from the Mecklenburg Bay and Arkona Basin were analysed in terms of their geochemical composition and stratigraphy. The main stages of the Baltic Sea evolution – Baltic Ice Lake, Ancylus Lake, and Littorina Sea – were identified in both analysed cores. The most pronounced period was the transition between the Ancylus Lake and the Littorina Sea. The character of the initial stage of the Littorina Sea was clearly defined in the Mecklenburg Bay sediments and is marked by a stepwise increase in loss on ignition and contents of biogenic silica, calcium, magnesium, iron, and strontium. The record of the onset of the Littorina Sea in the Arkona Basin sediments is marked by an abrupt change of the geochemical parameters. The age of the initial Littorina Sea in the Mecklenburg Bay was estimated at about 8200 cal years BP and was probably older than the transgression within the Arkona Basin.

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Stages of the Baltic Sea evolution in the geochemical record and radiocarbon dating of sediment cores from the Arkona Basin

Kostecki R.

Oceanological and Hydrobiological Studies

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2014

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Vol. 43, No. 3

237--246

EN

Four sediment cores from the southern part of the Arkona Basin were analyzed in terms of their geochemical composition, age and stratigraphy. The main stages of the Baltic Sea: the Baltic Ice Lake, the Ancylus Lake and the Littorina Sea were identified in all the analyzed cores. The data confirmed the high water fluctuation and significant environmental changes during the Baltic Sea evolution in the Late - Glacial and the Holocene. The signs of the second regression of the Baltic Ice L ake, dated at around 11 000 cal BP, were identified at a depth of 24 m b.s.l. Regression of the Ancylus Lake, dated at 9300 cal BP, was identified at a depth of 23 m b.s.l. The most pronounced period was the transition stage between the Ancylus Lake and th e Littorina Sea. The record of the Littorina Sea onset in the sediments of the Arkona Basin is marked as a sudden increase in loss on ignition, biogenic silica, magnesium, calcium, iron and strontium. The age of the Littorina Sea in the Arkona Basin was es timated as younger than 8200 cal BP.

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Agregaty halitowe współczesnych śródlądowych zbiorników słonych - reminiscencje z wypraw naukowych PSGS

Tomassi-Morawiec H., Czapowski G., Schramm M.

Geology, Geophysics and Environment

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2013

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Vol. 39, no. 3

279--289

PL

W brzeżnych partiach dwóch słonych zbiorników bezodpływowych: Morza Martwego w Izraelu (wyprawa PSGS w 2006 r.) i jeziora Tuz w Turcji (wyprawa PSGS w 2011 r.) napotkano sferyczne agregaty kryształków halitu. W Morzu Martwym„kulki" halitowe (o średnicy od kilku milimetrów do kilku centymetrów) zaobserwowano w strefie płytkiego przybrzeża z występowaniem wyraźnych prądów. W przypadku jeziora Tuz kuliste agregaty halitowe (o średnicy 0,5-0,7 cm) występowały na powierzchni skorupy solnej utworzonej w wyniku odparowania wód jeziora w okresie letnim. Formy z dna Morza Martwego to zapewne pizoidy, powstałe na bazie ooidów halitowych wskutek agradacji kryształków solnych wytrąconych z nasyconej względem halitu solanki i przetaczanych po dnie przez przydenne prądy wyrównawcze i falowanie sztormowe. Genezę „kulek" z jeziora Tuz należy prawdopodobnie wiązać z działalnością wiatru (halitowe „ooidy eoliczne") i są one produktem transportu eolicznego agregatów i pojedynczych kryształów halitu po odsłoniętej, chropowatej powierzchni skorupy solnej. Oznaczone w kilku „kulkach" zawartości bromu są zbliżone do wartości spotykanych w halitach powstałych z morskich solanek.

EN

In the nearshore parts of recent salt lakes - the Dead Sea (Israel) and the Tuz Lake (Turkey) - during the two PSGS excursions (2006' and 2011') spherical forms of fine-grained halite accumulation were found. These ones from the Dead Sea (few milimetres to few centimetres in diameter) were observed on the nearshore bottom with active bottom currents. The halite "balls" from Tuz lake Lake (0.5-0.7 cm in diameter) were observed on the salt crust surface that forms every year in dry season. It seems that crystal aggregates from the Dead Sea are the halite pisoids, formed due to continuous concentration of halite crystals, precipitated from the halite-saturated brines, onto the former fine halite ooids. Such forms became rolled and moved on the nearshore bottom by the bottom currents and storm waving. Salt "balls" from the Tuz Lake are rather of aeolian origin (halite "aeolian ooids") and they are the product of aeolian transport of the halite aggregates and crystals on the rough surface of exposed salt crust. The bromine content determined in few "balls" is similar to that observed in halites originated from marine brines.

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An attempt to resolve the partly conflicting data and ideas on the ancylus-littorina transition

Björck S., Andrén T., Bo Jensen J.

Polish Geological Institute Special Papers

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2008

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Vol. 23

21-26

EN

Lagoon gyttja layers occurring in anomalously high position (up to 2.5 m above the present-day sea level) The transition phase between the Ancylus and Littorina stages of the Baltic Sea is an old controversial topic. With the newest data available we try to reach a compromise between the "dramatic" model, including a sudden and large drainage of the Ancylus Lake, and the idea of a non-existing Ancylus drainage through Denmark. This new model includes a minor, perhaps 5 m, sudden erosion and forced regression slightly before 10,000 cal. yrs BP. This was followed by a 200–300 yr long period when the outlet through Denmark and Great Belt (Dana River) was characterized by a variable fluvial environment creating fluvial, levée and lacustrine deposits. During this period of rapidly rising sea level, we postulate that the gradient between the Ancylus Lake and sea level gradually decreased from some 5 m until sea level had reached the Ancylus and Darss Sill level. After this point in time occasional pulses of marine water could easier enter into the Baltic basin, which is seen as brackish pulses as early as 9800 cal. yrs BP in records from the Bornholm and Gotland basins, but also from Blekinge. It would, however, take another c. 1500 years before the Öresund threshold was flooded by the rising sea level, causing a significant rise in salinity sometime between 8500–8000 cal. yrs BP, and marking the true onset of the Littorina Sea.

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Evolution of the waterways and early human migrations in the North-Eastern Baltic area

Timofeev V. I., Dolukhanov P. M., Nosov E. N., Arslanov K. A., Subetto D. A., Zaitseva G. I.

Geochronometria

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2005

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Vol. 24

81-85

EN

The earliest evidence of human settlement in north-eastern Baltic Area is attested at Antrea-Korpilahti (9200-8250 cal BC) where Mesolithic artifacts were found in the deposits of a channel linking the Ancylus Lake and the Ladoga Lake. At the initial stage of the Littorina Sea, the Ladoga Lake became isolated and was drained into the Baltic Sea through the Palaeo-Vuoksa river system and the Veshchevo (Hejnijoki) Strait. The sites with the earliest evidence of pottery making (5560-5250 cal BC) coincided with the Littorina II stage. The connection of the Saimaa Lake basin with the Gulf of Bothnia was interrupted at 3000 cal BC, when the lake system started to drain into the Ladoga Lake via the Vuoksa (Vuoksi) River. Influx of fresh water caused a rise of the level of the Ladoga Lake. The peak of the ensuing "Ladoga transgression", was attained between 2210 and 1110 cal BC. At the peak of its transgression the Ladoga Lake formed a new outflow to the Baltic Sea via the Neva River. The current archaeological project is focused on early human migrations, land use and subsistence in relation to environmental changes with a special emphasis on the emergence and configuration of waterways.

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Paleolimnology in uruguay - a personal perspective

Garcia-Rodriguez F.

Studia Quaternaria

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2004

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Vol. 21

167-169

EN

Paleolimnological research only started in Uruguay in 1999 in the frame of the German-Uruguayan Academic Cooperation Program (DAAD-UDELAR). Research focused in costal lagoons and special attention was paid to the relationship between trophic development and sea level changes. Paleolimnology was also used as tool to assess human impact on aquatic water bodies and to provide a basis for the development of a management plan. Concomitantly, diatom taxonomy was also developed as diatoms are very well established indicators of paleoenvironmental change. In this sense, about 70 diatom species have been described as new for science.

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The water exchange in estuarine lakes of the southern Baltic Sea as on the Gardno Lake example

Jędrasik J., Cyberski J.

Oceanological Studies

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2000

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Vol. 29, No. 3

43-66

EN

The study of the Lake Gardno uses methodology that enables to estimate a magnitude of the sea inflows, their conditioning and timing as well as frequencies of their occurrence in lake estuaries. A three dimensional hydrodynamic model was applied to the linked regions of the Baltic Sea and the Gardno Lake. The quantitative estimates allow verifying the previous calculations of the water balance including long term changes.