Structural and Functional Organization of Phytoepiphyton of the Dnieper Reservoirs and Factors Influencing Its Development. Report 1. Role of Some Hydrophysical Factors

The paper considers the present-day taxonomic and ecological diversity, spatial patterns of phytoplankton and algae on the interface of two phases: water – substratum (microphytobenthos and phytoepiphyton) in the most typical biotopes of Kaniv Reservoir in summer seasons of 2017–2022. 301 species (311 intraspecific taxa) of algae have been identified from 142 genera, 75 families, 44 orders, 15 classes and 8 phyla. At the phyla level Bacillariophyta, Chlorophyta and Cyanobacteria dominated. The highest number of species and infraspecific taxa – 143 (146) have been found in microphytobenthos. The highest diversity at the level of genera (98), families (57), orders (37), classes (11) and phyla (7) was observed for the phytoplankton. The phytoplankton was dominated by Chlorophyta and Bacillariophyta, the microphytobenthos and phytoepiphyton – by Bacillariophyta. The highest level of species similarity has been recorded between the algal communities at the interface of two phases: water – substratum, the highest dissimilarity – between phytoplankton and phytoepiphyton. According to geographic distribution cosmopolite species prevail, according to saprobity – χ-ο- and β-mesosaprobic organisms, according to salinity preferences – indifferent species, according to pH preferences – alcalifilic species. According to biotopic preference typically planktonic and eurytopic forms dominate the phytoplankton, and benthic and eurytopic forms dominate the microphytobenthos and phytoepiphyton. Comparing the present-day findings with the retrospective data has not shown any significant changes in the phytoplankton and the microphytobenthos structures. As before, Chlorophyta, Bacillariophyta and, to a lesser extent, Cyanobacteria continue to dominate in phytoplankton, and Bacillariophyta and Chlorophyta – in microphytobenthos. It is explained by natural internal processes prevailing in Kaniv Reservoir, relatively stable level of human impact, and constant algal flow from Kyiv Reservoirs and tributaries. Nowadays phytoplankton, microphytobenthos and phytoepiphyton are distinguished by high taxonomic diversity and play an important role in Kaniv Reservoir biodiversity.

Section: вступunclassified

Section: матеріали та методиunclassified

Present-day characteristics of phytoplankton, microphytobenthos and phytoepiphyton of the Kaniv reservoir

Shcherbak,

Semeniuk,

Davydov

et al. 2023

“…Встановлено (Semenyuk, Shcherbak, 2016;Shcherbak et al, 2022), що при зростанні літньої температури води від 24,0 °С і вище (у наших дослідженнях -до 27,8 °С) у дніпровському фітопланктоні спостерігається більш інтенсивна вегетація Cyanobacteria (роди Dolichospermum (Anabaena), Microcystis, Oscillatoria) і пригнічення розвитку Bacillariophyta (роди Aulacoseira, Cyclotella, Melosira, Stephanodiscus), що, відповідно, впливає на загальні величини чисельності та біомаси водоростевих угруповань.…”

Section: результати та обговоренняunclassified

Present-day characteristics of phytoplankton, microphytobenthos and phytoepiphyton of the Kaniv Reservoir

Shcherbak,

Semeniuk,

Davydov

et al. 2023

The paper studies quantitative diversity and dominant complexes of phytoplankton, microphytobenthos and phytoepiphyton in lotic and lentic biotopes within the Kaniv Reservoir in summer seasons of 2017–2022, considers their association with some abiotic variables, assesses the trophic state, information diversity according to Shannon’s index and water quality. The cell count of planktonic algae varied within 2780–124155 thous. cells · dm–3, biomass – 0.631–11.636 mg · dm–3, benthic algae – 390–13874 thous. cells · 10 cm–2 and 0.162–2.651 mg mg · 10 cm–2, epiphytic algae – 50–680 thous. cells mg · 10 cm–2 and 0.050–1.679 mg · 10 cm–2 respectively. In lotic biotopes the phytoplankton cell count was higher than in lentic biotopes due to algal inflow from the Kyiv Reservoir and tributaries. The structural organization of phytoplankton and microphytobenthos is represented by oligodominant complexes of Cyanobacteria – Bacillariophyta and Bacillariophyta – Cyanobacteria respectively, and phytoepiphyton – by monodominant complex of Bacillariophyta. The necessity to distinguish dominant complexes according to cell count and biomass has been proven. The dominant complexes of algal communities clearly divide into three clusters (for plankton, benthos and epiphyton), and each of them – into two clusters (for lotic and lentic biotopes). The Sorensen similarity between phytoplankton and microphytobenthos was higher than between phytoplankton and phytoepiphyton, which can be explained by sedimentation of planktonic forms on the bottom under different ecological conditions. High cell count and biomass, diverse dominant complex of algal communities depend upon some abiotic variables (solar radiation, photic layer thickness, water temperature in summer, nutrient content). According to phytoplankton the trophic state of the Kaniv Reservoir is assessed as eutrophic–polytrophic, and according to contour algal communities – as oligo-mesotrophic–mesotrophic. This difference complies with the “alternative stable states” theory. That is, in summer the water reservoir is in “turbid state”, when planktonic Cyanobacteria grow intensively, screen the water surface and suppress the photosynthesis of benthic and epiphytic algal communities. The water quality of the Kaniv Reservoir is within the 1st–3rd classes (clean–satisfactory clean waters), there are no point of diffuse sources of water pollution, which mainly coincides with retrospective data.

“…Важливим компонентом автотрофної ланки водойм-охолоджувачів атомних електростанцій (ВО АЕС) є мікроскопічні водорості фітообростань (фітоперифітон). Відомо, що в таксономічному складі фітоперифітону провідне місце належить Bacillariophyta, які в основному представлені пеннатними формами (Кulikovskiy et al, 2016;Semenyuk, Shcherbak, 2016;Shcherbak et al, 2019). Висока різноманітність діатомей пояснюється тим, що незалежно від типу, походження та періоду експлуатації водойми-охолоджувача, в ньому представлена велика кількість твердих субстратів -від облицювання скидних каналів (підігрітих вод), водозабірних каналів (охолоджених вод, що надходять із джерел водозабору), різних дамб, відкосів до вищої водної рослинності.…”

Section: вступunclassified

“…Проби водоростей відбирали з кам'яних і деревних субстратів на станціях спостереження, розташованих у північно-східній, північно-західній, південно-східній і південно-західній частинах водойми (Shcherbak et al, 2018). Таксономічний склад водоростей визначали під світловим мікроскопом МББ-1А з окуляром 7, імерсійним об'єктивом 90 (Semenyuk, Shcherbak, 2016).…”

Section: матеріали та методиunclassified

Dynamics of periphytic Bacillariophyta at different stages of operation of the Chornobyl Nuclear Power Plant cooling pond (Ukraine)

Shcherbak¹,

Генкал²,

Semenyuk³

2021

The paper deals with the long-term dynamics of taxonomic composition of diatom periphyton in the Chornobyl nuclear power plant cooling pond (ChNPP cooling pond) at different stages of its operation: before the accident, after the accident and during the present period. The dominant complex of diatoms was marked by the highest diversity in the period after the accident, due to water temperature decreasing and new habitats appearing. The large-scale water-level drawdown in the present period caused the water table to reduce, and the habitats became less diverse. Owing to this, the number of dominant species decreased. Studying the present-day taxonomic composition of periphytic algae in the ChNPP cooling pond by way of light microscopy and scanning electron microscopy made it possible to identify 141 diatom species, represented by 143 infraspecific taxa, from 45 genera, 20 families, 12 orders and 3 classes. 14 species and infraspecific taxa of diatoms from genera Amphora, Cocconeis, Gomphonema, Hippodonta, Karayevia, Navicula, Placoneis, Planothidium, Psammothidium, Sellaphora are new for Ukrainian flora. High contamination of the ChNPP cooling pond with man-made radionuclides 90Sr, 137Cs and the large-scale water-level drawdown did not cause a significant degradation of diatom periphyton, which, in new ecological conditions, is distinguished by high taxonomic diversity and spatial heterogeneity.