scholarly journals Long-Term Studies Of Surface-Sediment Diatom Assemblages In Assessing The Ecological State Of Lake Ladoga, The Largest European Lake

2021 ◽  
Vol 14 (1) ◽  
pp. 251-262
Author(s):  
Anna V. Ludikova
Keyword(s):  
Surface Sediment ◽  
Lake Ladoga ◽  
Anthropogenic Pressure ◽  
Ecological State ◽  
Diatom Assemblages ◽  
Ecosystem Recovery ◽  
Phytoplankton Communities ◽  
The 1960S ◽  
Ecosystem State

The study continues a series of observations started in the late 1950s, aimed at inferring changes in the Lake Ladoga ecosystem state recorded in the surface-sediment diatom assemblages. At the pre-anthropogenic stage (prior to the 1960s), the composition of the surface-sediment diatom assemblages indicated an oligotrophic state of Lake Ladoga. With the increased P load to the lake (late 1960s–1980s), the transition to a mesotrophic state was recorded via increased proportions of eutrophic species and decreased abundances of the taxa typical of the pre-anthropogenic stage. In the early 1990s, the composition of the surface-sediment diatom assemblages still indicated a mesotrophic state despite a decreased external P load. At the present de-eutrophication stage of Lake Ladoga (the 2000s), the abundances of eutrophic taxa steadily decrease while some taxa typical of the pre-anthropogenic period return to their dominating position in the surface-sediment diatom assemblages. However, despite the decreased P concentrations, the Lake Ladoga ecosystem has not returned to its pre-anthropogenic state as indicated by the present-day composition of the surface-sediment diatom assemblages. This suggests a delayed ecosystem response to the decreased anthropogenic pressure, and possibly some irreversible changes resulting from the eutrophication. At present, de-eutrophication processes and ecosystem recovery are superimposed upon the recent climatic changes that govern the onset and duration of the vegetative seasons for the phytoplankton communities in Lake Ladoga. The diatom-inferred changes in the ecological state of Lake Ladoga are in agreement with the results of longterm hydrochemical and hydrobiological studies.

scholarly journals On the Issue of Assessing the Ecological State of Various Watercourses in the Conditions of Anthropogenic Pressure.

2021 ◽  
pp. 106-120
Author(s):  
Keyword(s):  
Water Pollution ◽  
Organic Matter ◽  
Desirability Function ◽  
Negative Relationship ◽  
Principal Component ◽  
Small Rivers ◽  
High Water Content ◽  
Anthropogenic Pressure ◽  
Ecological State

An assessment is given of the ecological state of nine rivers with different levels of anthropogenic load related to the Volga, the Don and the Ural basins. The water quality was assessed on the basis of several indices: the widely used specific combinatorial water pollution index (SCWPI), and statistical criteria based on the data of long-term environmental monitoring: the plasticity indicator as a measure of ecosystem sustainability and the desirability function. Hydro/chemical studies included indicators of oxygen regime, salt composition, organic matter, biogenic and toxic elements. The calculated SCWPI fluctuated in the range of 3,0–5,4, which corresponds to the quality category “very polluted” - “dirty”. The water of the lowest quality is in the small rivers Berezina and Elshanka, part of which is located in the industrial zone of the city of Saratov. The greatest contribution to the assessment of the degree of water pollution is made not only by the concentration of technogenic metals, but also by indicators of the content of organic matter, the amount of which depends on the level of bioproduction processes. The principal component analysis made it possible to structure the indices calculated for each river and to “explain” some of the information contained in the initial variables. Two main components were selected, based on the analysis results. The first factor integrates a negative relationship between the value of the UCIPI and the length of the river. Large rivers are more resistant to pollution due to their high water content. The second factor incorporated environmental criteria - the desirability function and the plasticity indicator, i.e. statistical indicators based on the data of long-term hydro/chemical monitoring and taking into account the real ecological state ̶ "health" of natural water systems and their sustainable functioning. Cluster analysis of the obtained statistical indices made it possible to divide the studied rivers by the quality of the aquatic environment into 4 groups.

Long-term changes in the phytoplankton of Lake Charzykowskie

2012 ◽  
Vol 41 (3) ◽  
Author(s):  
Marzena Wiśniewska ◽  
Marta Luścińska
Keyword(s):  
Catchment Area ◽  
Trophic Status ◽  
Physicochemical Analysis ◽  
Habitat Conditions ◽  
Phytoplankton Structure ◽  
Phytoplankton Communities ◽  
Long Term Changes ◽  
The 1960S ◽  
The Impact

AbstractThe research on phytoplankton communities in Lake Charzykowskie was carried out at intervals since the 1940s till the beginning of the 21 century. Long-term observations, initially of the species composition and in the following years also of the biomass and the concentration of chlorophyll-a in relation to habitat conditions, allowed to assess the impact of the catchment area on changes in the trophic status of the lake for over 50 years. And thus, based on the results of physicochemical analysis and studies on the phytoplankton structure in the 1940s, the lake was classified as ß-mesotrophic (Cabejszek 1950), between the 1960s and the1990s as eutrophic (Szulkowska-Wojaczek 1968, 1976; Wiśniewska 1994, 2000), in 2004 as hypertrophic (Wiśniewska 2005), and in 2008 and 2009 as meso-eutrophic.

scholarly journals Long-term studies for evaluating the impacts of natural and anthropic stressors on limnological features and the ecosystem quality of Lake Iseo

2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Barbara Leoni ◽  
Morena Spreafico ◽  
Martina Patelli ◽  
Valentina Soler ◽  
Letizia Garibaldi ◽  
...  
Keyword(s):  
Lake Ecosystem ◽  
Physical Parameters ◽  
Anthropogenic Pressure ◽  
Deep South ◽  
Two Factors ◽  
The 1960S ◽  
Biological Patterns ◽  
Zooplankton Communities

We review the state of the art of limnological studies in Lake Iseo and provide updated data concerning long-term investigations (from 1993 to 2018) carried out on chemical and physical parameters (e.g., oxygen, phosphorus, silicon). Changes observed in Lake Iseo were compared with those reported in other Deep South alpine Lakes (DSLs) to highlight analogies and differences of long-term chemical, physical, and biological patterns. Until the 1960s, Lake Iseo and other DSLs were oligotrophic. The increase of anthropogenic pressure and global warming has led to a progressive and unrecovered process of eutrophication. Moreover, the decrease in frequency of full mixing episodes has induced a state of temporary meromixis. Other changes have been identified over the last two decades, especially concerning the phytoplankton and zooplankton communities, and new emerging chemical pollutants were detected. Given the important ecological and socioeconomic role of Lake Iseo, long-term investigations are of paramount importance to understand the response of the lake ecosystem to climatic and anthropogenic stressors. These two factors can also act coupled with new combined and synergic effects.

Diatoms in the Early Valdai (Weichselian) sediments in Lake Ladoga basin

2019 ◽  
pp. 225-228
Author(s):  
Anna V. Ludikova
Keyword(s):  
Species Diversity ◽  
High Energy ◽  
Lake Ladoga ◽  
Diatom Assemblages ◽  
Marine Diatoms ◽  
Selective Preservation

The pioneer diatom study of the Early Weichselian (Valdai) sediments in Lake Ladoga basin was performed. The specifics of the diatom assemblages (co-occurrence of ecologically incompatible taxa, poor species diversity, low diatom concentration and selective preservation) suggest that during the Early Weichselian time intense erosion of previously deposited marine Eemian (Mikulino) sediments prevailed, which resulted in re-deposition of marine diatoms. The sedimentation took place in high-energy environments unfavorable for diatom accumulation and preservation.

scholarly journals High Mountain Asian glacier response to climate revealed by multi-temporal satellite observations since the 1960s

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Atanu Bhattacharya ◽  
Tobias Bolch ◽  
Kriti Mukherjee ◽  
Owen King ◽  
Brian Menounos ◽  
...  
Keyword(s):  
Mass Loss ◽  
River Flow ◽  
Tien Shan ◽  
High Mountain ◽  
Glacier Mass Balance ◽  
Temperature And Precipitation ◽  
Multi Temporal ◽  
The 1960S ◽  
Northern Tien Shan

AbstractKnowledge about the long-term response of High Mountain Asian glaciers to climatic variations is paramount because of their important role in sustaining Asian river flow. Here, a satellite-based time series of glacier mass balance for seven climatically different regions across High Mountain Asia since the 1960s shows that glacier mass loss rates have persistently increased at most sites. Regional glacier mass budgets ranged from −0.40 ± 0.07 m w.e.a−1 in Central and Northern Tien Shan to −0.06 ± 0.07 m w.e.a−1 in Eastern Pamir, with considerable temporal and spatial variability. Highest rates of mass loss occurred in Central Himalaya and Northern Tien Shan after 2015 and even in regions where glaciers were previously in balance with climate, such as Eastern Pamir, mass losses prevailed in recent years. An increase in summer temperature explains the long-term trend in mass loss and now appears to drive mass loss even in regions formerly sensitive to both temperature and precipitation.

scholarly journals Ecological Degradation of the Yangtze and Nile Delta-Estuaries in Response to Dam Construction with Special Reference to Monsoonal and Arid Climate Settings

Water ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1145
Author(s):  
Zhongyuan Chen ◽  
Hao Xu ◽  
Yanna Wang
Keyword(s):  
Regime Shift ◽  
Yangtze Estuary ◽  
Anthropogenic Sources ◽  
Arid Climate ◽  
Dam Construction ◽  
Nutrient Inputs ◽  
The Yangtze Estuary ◽  
Ecological Degradation ◽  
Phytoplankton Communities

This study reviews the monsoonal Yangtze and the arid Nile deltas with the objective of understanding how the process–response between river-basin modifications and delta-estuary ecological degradation are interrelated under contrasting hydroclimate dynamics. Our analysis shows that the Yangtze River had a long-term stepwise reduction in sediment and silicate fluxes to estuary due to dam construction since the 1960s, especially after the Three Gorges Dam (TGD) closed in 2003. By contrast, the Nile had a drastic reduction of sediment, freshwater, and silicate fluxes immediately after the construction of the Aswan High Dam (AHD) in 1964. Seasonal rainfall in the mid-lower Yangtze basin (below TGD) complemented riverine materials to its estuary, but little was available to the Nile coast below the AHD in the hyper-arid climate setting. Nitrogen (N) and phosphate (P) fluxes in both river basins have increased because of the overuse of N- and P-fertilizer, land-use changes, urbanization, and industrialization. Nutrient ratios (N:P:Si) in both delta-estuaries was greatly altered, i.e., Yangtze case: 75:1:946 (1960s–1970s), 86:1:272 (1980s–1990s) and 102:1:75 (2000s–2010s); and Nile case: 6:1:32 (1960s–1970s), 8:1:9 (1980s–1990s), and 45:1:22 (2013), in the context of the optimum of Redfield ratio (N:P:Si = 16:1:16). This led to an ecological regime shift evidenced by a long-term change in phytoplankton communities in the Yangtze estuary, where silicious algae tended to lose dominance since the end of the 1990s, when more toxic dinoflagellates began to emerge. In the Nile estuary, such a regime shift was indicated by the post-dam dramatic reduction in zooplankton standing crop and fish landings until the early 2000s when biological recovery occurred due to nutrient inputs from anthropogenic sources. Although the Yangtze had higher human impacts than the Nile in terms of population, industrialization, and fertilizer application, N concentrations in the Nile estuarine waters surpassed the Yangtze in recent decades. However, eutrophication in the Yangtze estuary is much more intensive than in the Nile, leading to the likelihood of its estuarine water becoming more acidic than ever before. Therefore, ecological degradation in both delta-estuaries does not follow a linear trajectory, due not only to different climate dynamics but also to human forcings. The comparative insights of this study should be incorporated into future integrated coastal management of these two important systems.

Environmental and spatial drivers of diatom assemblages in the water column and surface sediment of tropical reservoirs

2019 ◽  
Vol 62 (3) ◽  
pp. 245-257
Author(s):  
Elaine C. R. Bartozek ◽  
Angela M. da Silva-Lehmkuhl ◽  
Irene Gregory-Eaves ◽  
Denise C. Bicudo
Keyword(s):  
Water Column ◽  
Surface Sediment ◽  
Diatom Assemblages ◽  
Tropical Reservoirs

How the Desert got a Past: A History of Quaternary Research in Australia’s Deserts

2014 ◽  
Vol 25 (2) ◽  
pp. 172 ◽  
Author(s):  
Mike Smith
Keyword(s):  
Climate Changes ◽  
Conceptual Space ◽  
The Past ◽  
History Of ◽  
The 1960S

This paper examines how the past of desert landscapes has been interpreted since European explorers and scientists first encountered them. It charts the research that created the conceptual space within which archaeologists and Quaternarists now work. Studies from the 1840s–1960s created the notion of a ‘Great Australian Arid Period'. The 1960s studies of Lake Mungo and the Willandra Lakes by Jim Bowler revealed the cyclical nature of palaeolakes, that changed with climate changes in the Pleistocene, and the complexity of desert pasts. SLEADS and other researchers in the 1980s used thermoluminescence techniques that showed further complexities in desert lands beyond the Willandra particularly through new studies in the Strzelecki and Simpson Dunefields, Lake Eyre, Lake Woods and Lake Gregory. Australian deserts are varied and have very different histories. Far from ‘timeless lands', they have carried detailed information about long-term climate changes on continental scales.

Islamophobia

2019 ◽  
pp. 244-271
Author(s):  
Martin Pugh
Keyword(s):  
The United States ◽  
Islamic State ◽  
Islamic Fundamentalism ◽  
The West ◽  
Small Minority ◽  
Large Numbers ◽  
Proximate Causes ◽  
To Come ◽  
The 1960S

This chapter discusses how, misled by Islamophobic propaganda, Britain and America were unable to come to terms with what they called ‘Islamism’. The origins of what is variously known as Islamism, Islamic fundamentalism, and radical Islamism lie in the 1960s, in the ideas of a handful of Muslims in Pakistan, Egypt, and Iran who believed that Muslims had been led astray from their religion by nationalist movements. Although some Muslims were critical of Western morality and politics, Islamism was not primarily anti-Western: it was essentially a reaction against what were widely seen as the corrupt, authoritarian, and secular regimes that controlled much of the Muslim world. The aim was to evict them, return to a purer form of Islam and re-create an Islamic state. In view of the exaggerated reputation it enjoys in the West, it is worth remembering that this movement has largely been a failure. Yet while fundamentalism appeals to only a small minority, it is also the case that large numbers of Muslims have become aggrieved by the policies of the Western powers. The explanation for this can be found in long-term frustration with the consistently pro-Israeli policy of Britain and the United States over Palestine, in addition to the proximate causes in the shape of two Afghan wars, the genocide in Bosnia, the Rushdie affair, and the first Gulf War in 1990, which made many Muslims see themselves as the victims of Western aggression and interventionism.

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