Diet of European freshwater pearl mussels Margaritifera margaritifera (Mollusca: Bivalvia: Unionoida) in small river (Republic of Karelia, Russia)

The freshwater pearl mussel Margaritifera margaritifera (Linnaeus,1758) is endangered in Europe and is now listed in the Red Data Book of many countries and regions. The diet of the species in the Syskyänjoki River (a tributary of Lake Ladoga) has been studied. The contents of the intestine generally correspond to the composition of seston, and include organic detritus, filamentous and unicellular algae, fragments of invertebrates and macrophyte tissues mixed with silt and sand. The total biomass of the intestinal contents of varied from 0.8 to 30.6 mg per organism (absolutely dry weight). Margaritifera margaritifera consumes a wide range of particles, from 0.5 μm3 (bacteria and unicellular algae) to 200 000 μm3 (fragments of invertebrates and macrophyte tissues). About 90–95% (by volume) of the intestinal contents was consisted by fine organic detritus. The food composition did not differ significantly for mollusks of different sexes and size. In the intestinal contents, 63 taxa of algae were identified. The number of algal species in the content of one intestine varied from 3 to 17, with their abundance from 250 to 9560 cells per organism. The most abundant and constant in the contents of the intestines are unicellular algae. Diatoms are the most diverse, they make up 50.8% of the total number of species.

DYNAMICS OF THE BACTERIOPLANKTON STATE IN THE SHCHUCHIY BAY OF LAKE LADOGA AFTER THE CLOSURE OF THE PRIOZERSKY PULP AND PAPER MILL

Introduction. The Shchuchiy Bay is located in the western part of the skerry area of Lake Ladoga near the town of Priozersk. For almost 20 years, the bay has experienced an anthropogenic impact from the ingress of untreated wastewater from the Priozersk Pulp and Paper Mill (PPM). Systematic microbiological studies of the Shchuchiy Bay ecosystem were started in the middle of the 1970s by the Institute of Limnology of the Russian Academy of Sciences and continued after the PPM closure in 1986. Materials and methods. The ecosystem of the bay was studied in detail during the growing season of 2013–2014; periodic studies were carried out in 2015–2018. Retrospective data were also used for the analysis. Water samples were taken at four stations from the surface horizon. The following microbiological indicators were determined: the abundance of bacterioplankton and the percentages of various morphological types of bacterial cells. Results and discussion. A comparison of the quantitative level of development of the bacterial community in the bay in different periods showed a gradual decrease in the abundance of bacterioplankton as the anthropogenic impact weakened after the closure of the Priozersky PPM from 12.40 million cells ml–1 in 1987 to an average value of 2.62±1.03 million cells ml–1 in 2013–2018. A positive correlation was found between the concentration of bacteria and water temperature. The percentage of rod-shaped microorganisms in the water of the bay also decreased as the anthropogenic impact weakened from 73.4 % in 1987 to 53.1±7.6 % in 2013–2018, which indicated an improvement in water quality. Conclusion. A stable decrease in the abundance of bacteria from the level characteristic of highly polluted and eutrophic water bodies to the level characteristic of mesotrophic and mesotrophic-eutrophic water bodies is a reliable criterion for the restoration of the ecosystem of the Shchuchiy Bay to the state characteristic of similar bays of Lake Ladoga.

Epilithic lichen cover in assessing the quality of the coastal water environment in Karelia

The paper summarizes the data obtained by analyzing the reaction of the coastal epilithic lichen cover tothe chemical parameters of water in reservoirs of different types and uses. The study was carried out on the shores of freshwater bodies (Lake Onega, Lake Ladoga, Lososinka, Suna rivers) with different anthropogenic pressures in the Republicof Karelia. At each place of study, the lichen cover was described at the survey sites (frame 10 x 20 cm) along the transectand water samples were taken for chemical analysis. The aim of the work is to identify indicators of the coastal epilithic lichen cover to indicate the quality of the aquatic environment and assess the state of coastal ecosystems. The lichen flora ofthe surveyed coasts of fresh water bodies has 53 species, the highest species diversity of lichens is characterized by placeswithout obvious sources of pollution – the Kivach reserve (29 species), the shores of Lake Ladoga (27 species) and the Botanical Garden of PetrSU (16 species), and in urban conditions ( Petrozavodsk), a large settlement (Yanishpole) and nearthe pulp and paper industry (Kondopoga), the number of lichen species is much lower (8, 5 and 4). Regression analysisshowed the dependence of the number of lichen species on the registration site on the concentration of phosphorus compounds in water (p < 0.05). A tendency to a decrease in species diversity and a decrease in the total coverage of lichens withan increase in nitrogenous compounds in water was noted. This made it possible to propose the epilithic lichen cover as anobject-indicator of the state of the coastal water environment under conditions of anthropogenic pollution of water bodies.

Current state of bacterial community of Lake Ladoga

The data are presented on a quantitative assessment of the bacterioplankton community of Lake Ladoga and total bacterial numbers dynamic in the period from 2009 to 2019. The trophic state of the lake and water quality in different areas have been characterized by microbiological parameters. Maximum concentrations of microorganisms and highest water temperatures were commonly observed in the shallow coastal area (Volkhov Bay, up to 6.40 ×106 cells ml−1), and minimum – in the deepest part of the lake (ca. 0.45 ×106 cells cm−3). The bacterial abundances correlate with water temperatures both within each year of observations and over the whole study period. The trophic state of the lake expressed by the total bacterial numbers during summer seasons closely matches the state during the first decade of the 21st century. In the period of 2009-2019, the trophic state varied from oligo-mesotrophic in the hypolimnion of deep-water areas to mesotrophic eutrophic in the shallow southern coastal area, which corresponds to the trophic state indicated by chlorophyll-a concentrations. Within the previous decade (2000-2008), the waters of Lake Ladoga were “clean” and “especially clean”, while during the 2017-2019 period, water masses all over the lake can be identified as “especially clean”. From 2017 to 2019 the coccoid forms of bacterial cells prevailed over rod-shaped cells comprising 57.6 ±5.1% (2017), 64.4 ±4.5% (2018), 61.1 ±4.6% (2019), which imply the high quality of the waters.

Laatokka: Suurjärven kiehtova rantahistoria

For the first time worldwide, this collection brings together analyses of the last two centuries of historical change around the shores and drainage basin of Lake Ladoga, Europe’s largest lake. The main focus of the narrative is the Northern Ladoga region, which was a Finnish administrative area between 1812 and 1944. After the Second World War, the entire shoreline of Lake Ladoga was incorporated into the northeast part of Russia’s border region, the Autonomous Republic of Karelia and the Leningrad Province. The main theme uniting this collection is how the relationship between humans and nature is shaped by industrialization and modernization in society. Other key issues include protecting nature and perspectives on particular places and times, which are reflected in the methodological and thematic choices made in this volume. The research framework set by the editor, Professor Maria Lähteenmäki, is the new lakefront history (Finn. uusi rantahistoria), focusing on approaches to environmental, economic and sensory history of lakes. To draw broad conclusions, on the one hand, the multilevel changes on the lakefront cannot be understood without knowledge of the history of the wider drainage basin, and awareness of the geopolitics of the region and the climate changes. On the other hand, the human relationship to natural waters has changed significantly in 200 years. Thinking in terms of economic benefit has gradually given way to principles of sustainable development. Lake Ladoga is also being redefined from a spatial perspective, as nationalist ownership of the region is coupled with global concern about the state of Europe’s largest lake.

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

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.