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Bloom of the potentially toxic cyanobacterium P. rubescens : seasonal distribution and possible drivers of its proliferation in the Vrutci reservoir (Serbia)

Ponjavić Ana Blagojević, Kostić Dušan, Marjanović Prvoslav, Trbojević Ivana, Popović Sladana, Predojević Dragana, Simić Gordana Subakov

Oceanological and Hydrobiological Studies

2019

Vol. 48, No. 4

316--327

Planktothrix rubescens is a filamentous cyanobacterium with a worldwide distribution in lakes and reservoirs of varying size and morphology. The objective of this study was to identify the population dynamics and the major drivers of P. rubescens blooms. Samples for qualitative and quantitative analysis of phytoplankton were collected every month in 2014 and 2015 from stationary depths, while the main physical parameters were measured in situ along the water column. Samples for chemical analysis were collected below the surface, at mid-depth (metalimnion) and near the bottom. In the periods of thermal stratification, P. rubescens formed the maximum biomass in the metalimnion, however, its volume-weighted biomass reached the maximum value in the winter mixing period (4.40 mm3 l−1). Changes in the P. rubescens population in the reservoir were related to changes in the measured environmental parameters. Significant physical, hydrological, meteorological and chemical parameters were distinguished based on the multivariate analysis. The variable associated with water-level fluctuations showed the highest positive correlation with P. rubescens biomass. We conclude that it is necessary to establish water quality monitoring and prevent excessive water-level fluctuations to ensure a high quality of water supplies from the reservoir.

Dynamika wahań poziomu wody na zdegradowanych torfowiskach bałtyckich

Duda F., Woźniak E., Jereczek-Korzeniewska K., Cieśliński R.

Przegląd Geologiczny

2017

Vol. 65, nr 8

526--532

Baltic-type raised bog (dome-shaped) is a type of peatbog with predominant atmospheric water supply and a convex shape, known as the dome. In Poland, 72 Baltic peatbogs have been distinguished, with various degrees of transformation, in the coastal zone and lake districts of the South Baltic Sea. None of them has natural water conditions. Their common name indicates significant similarities due to water supply conditions. However, due to the differences in morphology, both primary and secondary (resulting from the different course and scale of anthropogenic transformations), they may be expected to show some variability within the subtype. The aim of the paper is to present the diversity of water-level fluctuations in degraded Baltic raised bogs. An attempt was made to answer the question how strong the diversity of fluctuations is, both within each object and between two objects situated close to each other. Moreover, speed and value of the response of water level to atmospheric precipitation were analysed. The spatial scope of the paper covers two Baltic raised bogs in the lower part of the Łeba River valley: Czarne Bagno and £ebskie Bagno. To answer the questions asked, the results of measurements of water level and precipitation on the peat bogs were used. The study found that both the bogs show high dynamics in the variation of groundwater level. Lowering of the water level on both peatlands has always been recorded in the summer months, whilst its increase, which lasted until spring, has been observed in autumn. The water retention amount and water level on the peatlands were influenced primarily by precipitation. Extreme meteorological conditions that make it less conspicuous is the variation resulting from factors such as location in different parts of the bog, or type of degradation.

The Holocene sedimentation history of Lake Vortsjärv, central Estonia

Raukas A., Tavast E.

Geological Quarterly

2002

Vol. 46, No 2

199-206

Lake Vortsjärv is one of the biggest lakes in Eastern Europe and possesses a complex geological history. Bottom deposits consist mostly of fine sand and silt, accompanied with sapropel (up to 9 m thick) and lake marl (up to 8 m thick). In places, especially in the northern part where the bottom deposits are absent, varved clay or till are exposed in the lake basin. In the southern part of the lake the deposits are much thicker, indicating a gradual rise of water-level. Like the majority of lakes in the Northern Hemisphere, Lake Vortsjärv possesses a more open eastern and a more swampy and overgrown western bank. Shore types and the lithological composition of shore sediments are varied and highly controlled by the bedrock and glacial deposits. Long-shore transport of sediments is limited. The mineral composition of bottom sediments shows great qualitative and quantitative variability which relates to the grain-size and petrography of the parent deposits. Organic-rich sapropel can be used in agriculture and evidently also for medicinal purposes.