Changes in Algal Species Composition of Alpine Lake Nesamovyte (Eastern Carpathians, Ukraine) from 100 Years Ago to Present

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Benthic Diatom Composition in Coastal Zone of Black Sea, Sasyk Reservoir (Ukraine)

The Sasyk Reservoir is one of the largest seaside reservoirs in Ukraine, artificially maintained as a freshwater area including various floodplain areas. The Reservoir originated from an estuary to now being an almost freshwater reservoir. The diatoms (Bacillariophyta) in benthos were investigated for analyzing the coastal zone diversity of the Black Sea inside the borders of Ukraine. The indicated diatom composition was formed by 97 species (100 infraspecies taxa). Some rare marine and freshwater taxa were noted, as well as three species reported in Ukrainian territory for the first time (Navicula vandamii Schoeman et R.E.M. Archibald, Sellaphora difficillima (Hustedt) C.E. Wetzel, L. Ector et D.G. Mann, and Mastogloia laterostrata Hustedt). The bioindicative characteristics of the diatom composition testified to the freshwater condition of the reservoir. Changes to the salinity level of the Sasyk Reservoir were exposed due to the composition of benthic diatoms. The presence of mesohalobous species (7 taxa) acknowledges conditions that are typical for estuaries and mouths of rivers and reveals the salinity changes in the Sasyk Reservoir. Likewise, the prevailing number of oligohalobous diatoms (61 taxa) reveal presence of freshwater in the reservoir. The implementation of the Polish phytobenthos lake assessment method for the nearby Ukrainian Reservoir was conducted for the first time. The multimetric Diatom Index for lake values varied from 0.39 to 0.76, and revealed alterations in the status over the Sasyk sites, ranging from good, moderate, to poor. Thus, it may be concluded that the current ecological status relating to the composition of benthic diatoms of the reservoir located in the coastal zone of the Black Sea is evaluated as having a moderate status class with some exceptions

Centric diatom diversity in the lower part of the Southern Bug river (Ukraine): the transitional zone at Mykolaiv city

The diversity of centric diatoms is documented for the transitional zone of the lower part of the Southern Bug River (Ukraine) just before entering the Dnipro-Bug Estuary and compared to earlier results from the upstream sampling sites of the same river system. Benthic samples of the following sites were investigated: north of Mykolaiv City (approximately 5 km), in Mykolaiv City (near Varvarivskyi Bridge), and 5 km south of the city. Twenty-four centric diatom taxa belonging to 11 genera were identified, analysed, and documented by scanning electron microscopy (SEM) and light microscopy (LM). Among them, Aulacoseira nivalis is the first report for Ukraine, A. islandica and is the first confirmed record for the studied area since the 1930s. The maximum number of centric diatom taxa found in one station was 21, the minimum 10. Melosira subglobosa was the most common (documented in 57–80% of sites with centric diatoms) and abundant species 7.3–15.7% in relative abundance to all diatom taxa. The discovered diversity of taxa and its comparison with previous results is discussed with regard to the relevance of estuary zones in the research of diatoms

Interactions between Aquatic Plants and Cyanobacterial Blooms in Freshwater Reservoir Ecosystems

Climate change and nutrient pollution are echoed by worldwide increasing trends in the frequency, duration, and toxicity of cyanobacterial (blue-green algal) blooms. Therefore, searching for the best options to mitigate blooms is relevant and timely. Aquatic vascular plants offer a promising solution through biological control. In this study, we use reservoirs regularly affected by intensive blooms (the Kyiv and Kaniv Reservoirs of the Dnipro River, Ukraine) to investigate whether macrophytes may inhibit or reduce the massive development of cyanobacteria. Special attention was paid to plants with floating leaves and free-floating plants since data on their effects on cyanobacteria are controversial. On the basis of field and satellite observations, the spatial distribution of cyanobacterial blooms and aquatic macrophyte patches was assessed. Multispectral images captured by satellites Sentinel-2a (S2A) and Sentinel-2b (S2B) were used. In addition, based on data from field observations, a comparative analysis of phytoplankton and physical and chemical parameters between areas of the reservoirs overgrown and not overgrown by macrophytes was carried out. The obtained results indicate that in macrophyte patches phytoplankton structure differed from that observed in open waters. However, in areas of reservoirs dominated by floating-leaf plants or free-floating plants, a significant decrease in phytoplanktic or cyanobacterial biomass was not observed. This is most likely due to the fact that these macrophytes did not reduce the concentration of biogenic substances to a level that would limit cyanobacterial growth. On the contrary, intensive overgrowth of floating-leaf plants (in particular, Trapa natans) along the river sections of the reservoirs, as well as other factors, contributed to nitrogen and phosphorus enrichment. Therefore, in the face of relevant nutrient supply, these ecological groups of macrophytes (floating-leaf plants and free-floating plants) have not shown statistically significant effectiveness in controlling the process of cyanobacterial blooms in reservoir ecosystems

Diatom Indicators of Fluctuating/Intermittent Discharge from Springs in Two Bavarian Nature Conservation Areas

As a follow-up to the project “Springs in the Bavarian National Parks as Indicators of Climate Change (SpringNPB)”, a standard methodology for using springs as sentinel environments of climate change was transferred to the UNESCO Rhön Biosphere Reserve and other Bavarian middle-elevation mountain ranges. We studied diatoms from fifteen springs selected in the UNESCO Biosphere Reserve (9) and Steigerwald Nature Park (6). A total of 127 species belonging to 40 genera were found sampling 3 microhabitat types (lithic materials, hygrophilous or aquatic vegetation, and surface sediments). The cumulative percentage of endangered species according to the Red List was 41.5%. These very shaded, low–medium conductivity, low-discharge forest springs are fed by small surficial aquifers. As a consequence, the discharge fluctuates widely, and some springs even occasionally fall dry. Our results could contribute to the use of diatoms as indicators of discharge variability/desiccation in springs: springs affected by discharge variability have lower diatom species richness and distinct diatom communities; diatom indicators and metrics can be validated using invertebrates; larger databases will be necessary to identify the most suitable diatom indicators