Phytoplankton Species Composition Research Articles

Impacts of counting protocols for light microscopy on estimates of biodiversity and algal density of phytoplankton

AbstractKnowledge on the biodiversity and abundance of phytoplankton is key for many ecological and societal (e.g., blue growth) questions. Gathering temporal variation and spatial patterns on key indicators requires reliable and standardized protocols on sampling, species identification and counting. Numerous methods are used but consequences for comparing the biodiversity and abundance of phytoplankton of these different techniques are not well known. We evaluated the consequences of different counting protocols using light microscopy (i.e., subsampling transects or wedges within counting chambers) for these indices using samples collected weekly to bi‐weekly (n = 398, 2009–2018) from the Wadden Sea (southern North Sea). Phytoplankton cells were counted (by one person under similar conditions) in a fixed number of viewing fields (58, 70, and 29) at three respective magnifications (10 × 100, 10 × 40, and 10 × 10). Patterns in the spatial distribution of phytoplankton cells varied among species and clustering of cells occurred in more than one‐fifth of the samples. This will induce error in the conversion from counts (per viewing field) to abundance (cells mL−1). Our present effort resulted in a high accuracy (95%) in overall cell abundances. This was not the case for species richness, for example, capturing 90% of all species present in the sample would require an almost threefold increase in effort for the 10 × 40 and 10 × 10 magnifications. We recommend that counting methods be tailored to the main research objectives and that counting protocols should quantify uncertainty as well as potential bias to provide an estimation of the error in phytoplankton abundance and species composition.

A Comparative Study of Phytoplankton Communities and Eutrophication Status in Two Urban Ponds Within Dhaka Metropolis

Changes in physicochemical water quality and plankton biomass over time can clearly indicate the eutrophication status of a water body. Urban ponds are particularly susceptible to cultural and natural eutrophication, making it essential to study their water quality and phytoplankton biomass. This study examined two urban ponds within the University of Dhaka campus: Shahidullah Hall Pond (SH-pond) and Museum Pond (Mu-pond). Common phytoplankton in both ponds included species like Pediastrum simplex, Melosira granulata var. angustata, Synedra nana, Ceratium sp., and Ceratium furcoides, along with zooplankton such as Brachionus sp., Keratella cochlearis, and copepod nauplii. The higher diversity of zooplankton compared to phytoplankton suggests that zooplankton overgrazing has reduced phytoplankton species composition. The study’s results indicate a clear trend of eutrophication in both ponds. Over three decades, SH-pond showed increases in water temperature (4.5°C), alkalinity (0.32 meq/L), dissolved oxygen (6.84 mg/L), soluble reactive phosphorus (21.35 μg/L), nitrate (137.77 μg/L), and chlorophyll-a (23.76 μg/L), with water transparency decreasing by 67 cm. Eutrophication indicators like dissolved oxygen, nitrogen, phosphorus, and phytoplankton biomass (chlorophyll-a) increased by 1.9, 1.82, 2.23, and 2.21 times, respectively, suggesting significant eutrophication in Sh-pond. In contrast, over 26 years, Mu-pond data showed decreases in water temperature (2.66°C), pH (0.18), conductivity (31 μS/cm), silica (12.17 mg/L), and chlorophyll-a (12.4 μg/L), but increases in dissolved oxygen (7.61 mg/L), soluble reactive phosphorus (1.16 μg/L), and nitrate nitrogen (170.75 μg/L). This suggests a slower rate of eutrophication in Mu-pond. Human intervention is a critical factor influencing eutrophication in urban ponds, highlighting the need for effective management systems. Dhaka Univ. J. Biol. Sci. 33(2): 15-26, 2024 (July)

Phytoplankton community structure at the eastern entrance of the Gulf of California during El Niño 2023

This work aims to report the phytoplankton species composition and cell density in the Mazatlán coastal region (eastern entrance of the Gulf of California (GC), Mexico) during the strong El Niño event of 2023. Surface water samples (at 2 m depth) for phytoplankton cell determinations were collected in December of 2023, a month in which the numerical value of the Oceanic Niño Index was 2.0. The results showed a total of 197 species, including 113 diatoms (with a total cell density of 51,444 cells L-1), 76 dinoflagellates (with a total cell density of 31,260 cells L-1), four silicoflagellates (with a total cell density of 420 cells L-1), two cyanobacteria (with a total cell density of 2,020 cells L-1), one Euglenophyta (with a total cell density of 900 cells L-1) and one ciliate (with a total cell density of 7,820 cells L-1). The diatom Dactyliosolen phuketensis (B.G.Sundström) G.R. Hasle, 1996 and the dinoflagellate Gyrodinium fusiforme (Kofoid & Swezy, 1921) presented the highest cell densities with 4,100 and 5,900 cells L-1, respectively, species that have been previously reported in high abundances in Mexican waters in years of warming events, including El Niño. The results presented here contribute to understanding the effects of strong El Niño events on the phytoplankton community structure of the southeastern GC. This topic still needs to be fully addressed. This study also provides an update on the taxonomic lists available for the region of a group of organisms whose nomenclature has been constantly changing in recent years.

Structure of phytoplankton for the coastal waters in the eastern Aniva Bay of the Okhotsk Sea in 2018

Species composition, distribution density and biomass of phytoplankton were surveyed in the coastal area of eastern Aniva Bay in May-October 2018. In total, 297 species and intraspecific taxa of microalgae belonged to Bacillariophyta, Chlorophyta, Cryptophyta, Dinophyta, Euglenophyta, Crysophyta were found. Their total abundance ranged from 14.8 . 103 to 1024.7 . 103 cells/L, biomass was 19.4–324.6 mg/m3. Two peaks in the abundance (in June and October) and five peaks in the biomass (in May, June, September and October) were noted. The bulk of population was formed by diatoms in spring and autumn, and flagellates in summer. A bloom of potentially toxic diatoms of genus Pseudo-nitzschia was registered. In this connection, monitoring of toxic species is necessary for planning and development of aquaculture farms.

Plankton and benthos in Lake Blagodatnoye (Iturup Island) in summer

Lake Blagodatnoye is an oligohaline meromictic reservoir with the two-layer vertical structure — a typical lagoon lake for the southern Far East of Russia. Its upper layer is occupied by fresh water and the lower layer — by brackish water. The greatest warming of water (up to 22 оC) is observed at the lake surface in late July — early August. In total, 274 species are found in phytoplankton of the lake that is the largest number among all surveyed lagoon lakes in the south of Sakhalin-Kuril region. Bacillariophyta form the basis of the phytoplankton species composition (64 % of species). Abundance and biomass of the phytoplankton vary widely from 1.15 . 106 to 160.44 . 106 cells/L and from 0.41 to 6.14 g/m3, respectively. Several peaks are noted in seasonal dynamics of these indices. Zooplankton in the lake includes 25 species. All these species are typical for lagoon lakes in the south of Sakhalin-Kuril region. Wide variations in abundance and biomass are noted for the zooplankton: from 10550 to 99350 ind./m3 and from 47.1 to 231.0 mg/m3, respectively. Two types of species composition are identified in the summer succession of the phytoand zooplankton communities. The phytoplankton groups change at the border between June and July, when temperature at the surface passes the value of 14–16 оC. The key species of the early-summer phytoplankton are Cyanobacteria of genera Aphanocapsa, Chroococcus, Microcystis, Anabaena and Bacillariophyta of the genus Asterionella, whereas Aulacoseira granulata and A. granulata var. angutissima are the most abundant in late summer. For zooplankton, the boundary between the early-summer and late-summer seasons is shifted to middle July when the water temperature rises to 17–18 оC. Rotifera of Asplanchna priodonta, Cladocera of Bosmina sp., younger copepodites of Cyclops and Eurytemora caspica tethysiana dominate in early summer, whereas Bosmina sp. and juveniles of Cyclops — in late summer. Macrozoobenthos in the lake is represented by 25 species of invertebrates. The basis of species diversity is formed by amphibiotic insects. Number of species and total distribution density and biomass of macrozoobenthos mostly declined with the depth: there were 18 species, 370 ± 50 ind./m2, 3.023 ± 0.459 g/m2 in the intertidal zone, 14 species, 580 ± 59 ind./m2, 3.477 ± 0.447 g/m2 in the elittoral zone, and 10 species, 364 ± 36 ind./m2, 2.110 ± 0.248 g/m2 in the profundal zone, and dominant species were changed from Amphipoda Eogammarus barbatus in the intertidal zone to Chironomidae Chironomus dorsalis in the elittoral zone and to Gastropoda Cincinna japonica, Oligochaeta Lumbriculus variegatus and Chironomidae C. dorsalis in the profundal zone. The phytoplankton production in the coastal zone (depth of 0–3 m) was estimated as 552.86 kcal/m2 in June-August. Zooplankton consumed only 0.7 % of this production and produced 767 cal/m2. The production of non-predatory zoobenthos was 8644 cal/m2, with the inputs of 70.2 % for detritus feeders of 70.2 %, 11.8 % for macroalgae feeders, 11.6 % for deposit feeders, 5.8 % for grazers, and 0.6 % for filtered suspension feeders. A part of this production (6.9 %) was transmitted to the feed of carnivorous zoobenthos, so 8286 cal/m2 of the macrozoobenthos production could be used for fish feeding in the coastal zone. The phytoplankton production in the open waters (depth of 3–9 m) was estimated in 2580 kcal/m2. Zooplankton consumed 1.01 % of this production and produced 3578 cal/m2. The production of non-predatory zoobenthos in this zone was 6179 cal/m2 (detritus feeders 68.1 %, deposit feeders 18.8 %, grazers 6.6 %, macroalgae feeders 3.0 %, and filtered suspension feeders 3.5 %). The portion of 12.7 % of this production was transmitted to the feed of carnivorous zoobenthos. The total macrozoobenthos production in the open waters was 5708 cal/m2. The total reserve of food for fish, including zooplankton and benthos, was evaluated in 9286 cal/m2.

Assessing alternative lake management actions for climate change adaptation.

Lake management actions are required to protect lake ecosystems that are being threatened by climate change. Freshwater lakes in semiarid regions are of upmost importance to their region. Simulations of the subtropical Lake Kinneret project that rising temperatures will cause change to phytoplankton species composition, including increased cyanobacteria blooms, endangering lake ecosystem services. Using lake ecosystem models, we examined several management actions under climate change, including two alternatives of desalinated water introduction into the lake, hypolimnetic water withdrawal, watershed management changes and low versus high lake water level. To account for prediction uncertainty, we utilized an ensemble of two 1D hydrodynamic-biogeochemical lake models along with 500 realizations of meteorological conditions. Results suggest that supplying desalinated water for local use, thus releasing more natural waters through the Jordan River, increasing nutrient flow, may reduce cyanobacteria blooms, mitigating climate change effects. However, these results are accompanied by considerable uncertainty.

Microzooplankton and phytoplankton of Ross Sea polynya areas and potential linkage among functional traits

The Ross Sea is characterized by a series of subsystems with different characteristics making it an extremely productive area. To understand whether species composition and functional traits of the plankton community can be used as biological tracers, we have analyzed the composition of phytoplankton and microzooplankton, and their potential relationships, in two different polynyas of the Ross Sea during the austral summer 2017. Sampling activities were carried out near Terra Nova Bay, between Cape Washington and the northern shore of the Drygalski Ice Tongue, and in the South-Central Ross Sea. We investigated the phytoplankton and microzooplankton structure using the phytoplankton body size classes and the tintinnids lorica oral diameter as functional traits, speculating on the relationship between the two plankton communities and their use as biological indicators in a changing Southern Ocean. Our data showed significant differences in terms of plankton composition and related functional traits between the two areas, suggesting the existence of distinct ecological dynamics despite the similar total carbon content. In Terra Nova Bay, heterotrophic dinoflagellates were the most abundant microzooplankton, in association with a large phytoplankton biomass mainly represented by diatoms and nano- and micro-phytoplankton. Tintinnids with large lorica oral diameters were abundant in Central Ross Sea, where phytoplankton was dominated by Phaeocystis antarctica and by the micro size class. Among microzooplankton, Protoperidinium defectum, P. applanatum and P. incertum were the most abundant dinoflagellates species, while Codonellopsis gaussi, C. gaussi forma cylindroconica, Laackmanniella prolongata and Cymatocylis drygalskii were the most abundant tintinnids. The phytoplankton was dominated by diatoms Pseudo-nitzschia subcurvata, Fragilariopsis cylindrus, F. curta and by the haptophyte P. antarctica. Our data indicate that beyond physical and chemical features defining distinct sectors of the Ross Sea, both species composition and functional traits of phytoplankton and microzooplankton represent a valid monitoring tool, especially with the ongoing global warming and its effects on Antarctic food webs.

Phytoplankton composition in Mediterranean confined coastal lagoons: testing the use of ecosystem metabolism for the quantification of community-related variables

Estimations of ecosystem metabolism have rarely been used to quantify productivity in structural reductionist approaches for the description of phytoplankton composition. However, estimations of ecosystem metabolism could contribute to a better understanding of the relationship between phytoplankton composition and ecosystem functioning. To examine this, we investigated the community structure of phytoplankton in a set of Mediterranean coastal lagoons (natural and artificial) during a hydrological cycle to identify the most important environmental variables determining phytoplankton species composition. The focus of the study was on the quantification of productivity-related variables using estimations of ecosystem metabolism, such as different proxies for the estimation of the production-to-biomass ratio and of the relative importance of K- and r-strategies, which are commonly used conceptually but not quantified. Our results demonstrated differences in phytoplankton composition between seasons, due to the dominant hydrological pattern of flooding confinement in the salt marsh, and between lagoons that were caused by different levels of nutrient availability. Moreover, there was a notable decrease in the production/biomass ratio and a prevalence of K-strategists with seasonal succession, as predicted by Margalef’s mandala. Thus, the results showed that estimations of ecosystem metabolism are useful for the higher frequency quantification of important ecological variables, and contribute to a better understanding of planktonic assemblages, and physical and chemical changes, in these fluctuating ecosystems.

Multi-year three-dimensional simulation of seasonal variation in phytoplankton species composition in a large shallow lake

Lake Erie has been negatively impacted by multiple stressors, including nutrient enrichment and climate change, that have exacerbated eutrophication and harmful algal blooms. Management of these long-term water quality problems requires numerical models that can be run over years to decades. The three-dimensional hydrodynamics and biogeochemistry models applied to date, however, have not been tested for continuous runs longer than one year and have not been shown to accurately reproduce seasonal variation in phytoplankton species composition (e.g., the development of harmful algal blooms) over decadal timescales. We simulated the three-dimensional nutrient and phytoplankton concentrations in western Lake Erie continuously from 2002 to 2014. Using a single parameter set, we were able to reproduce both seasonal and inter-annual variation in phytoplankton species composition. The model qualitatively reproduced the observed seasonal succession (i.e., variation in phytoplankton species composition), including the spring diatom bloom and late summer cyanobacterial growth. This study demonstrates that three-dimensional models can be applied for multi-year simulations of nutrients and phytoplankton to inform large lake research and management.

Detection of Autumnal Concentration of Coscinodiscus granii in the Southern Baltic—A Method for In Situ Measurement of Marine Particles

Efficient means for measuring the abundance and species composition of phytoplankton in situ continue to pose a big challenge to scientists. Hitherto, analyses and interpretations have been based mainly on small numbers of data acquired from microscopic examinations of water samples. Hence, information on devices facilitating such measurements is highly desirable. This paper examines the opportunities offered by the LISST-100X instrument for measuring in situ the concentrations and spatially variable biovolumes of a species dominant in the southern Baltic during the autumnal bloom. Microscopic analysis of phytoplankton in water sampled from different locations in the southern Baltic confirmed earlier results, indicating that this bloom was due to the overriding prevalence of one microplankton diatom species—Coscinodiscus granii. Combining the microscopic measurements of C. granii cell sizes with the size distribution ranges employed by the LISST-100X yielded equivalent spherical diameters (EDSs) ranging from 47.4 to 188.0 µm, with maxima in the 78.4–92.6 and 92.6–109 ranges. Comparative analysis of the particle size distribution (PSD) spectra was used to separate the abundance of C. granii from the total suspended particulate matter (SPM). Spatial in situ measurements in 2012 and 2014 of C. granii concentrations in surface waters showed that both its abundance and its percentage contribution to the total SPM were highly variable. Over a distance of several km, these concentrations varied from values close to zero to 0.2 µL L−1 in 2012 and from 0.3 to 0.9 µL L−1 in 2014, whereas the percentage in the total SPM was found to vary locally from a few to c. 50%. The proposed method and results demonstrate the success of the LISST-100X instrument in detecting size and volume concentrations of phytoplankton in size classes ranging from 1.25 to 250 μm. However, the correct interpretation of LISST data requires that the dominant phytoplankton species concentration in the suspensions be large enough for the signal (peak) to be readily visible against the background PSD of other SPM.

Effect of wind–wave conditions on the distribution of the phytoplankton community in the coastal area of the southern Crimea in spring (Black Sea)

Based on the measurement data obtained during the 121th cruise of the RV Professor Vodyanitsky, regularities were established between spatial distribution of quantitative characteristics and phytoplankton species composition, chlorophyll a concentration, and hydrometeorological parameters of the environment on the southern Crimean coast in the spring 2022. Chlorophyll a concentration was compared with satellite observation data of high spatial resolution. In selected areas with different shelf depths, the features of the distribution of phytoplankton indicators under conditions of changing hydrometeorological parameters were studied. The mechanisms of vertical water exchange were described. In coastal waters of the Crimea (Foros–Novy Svet), with intense western wind contributing to Ekman upwelling and low water temperature is a consequence of the upwelling, rather high values of phytoplankton biomass and abundance and chlorophyll a concentration were recorded, which were accompanied by the highest values of oxygen content. In the area of Sudak–Feodosiya, with intense northeastern wind and waves and with quite high water temperature, low dissolved oxygen, low values of phytoplankton biomass and abundance and chlorophyll a concentration were registered. Apparently, in Sevastopol area, Ekman upwelling arises under the effect of northern and northwestern winds. In three regions, dinoflagellate microalgae prevailed in spring 2022 in phytoplankton biomass. Those accounted for 52, 66, 81 % of the total number of species identified in the regions: Foros–Novy Svet, Sudak–Feodosiya, near Sevastopol, respectively. Thus, the main mechanisms were analyzed, which drive spatial distribution of quantitative characteristics and species composition of the phytoplankton community in the Crimean coastal water area with different shelf depths in spring.

Phytoplankton Species Composition in the Turkish Coast of the Aegean Sea between 2014 and 2016

The research was carried out between 2014 and 2016, within the scope of the ‘National Integrated Marine Pollution Monitoring Program,’ in a total of five seasonal cruises at 22 stations along the Turkish coast of the Aegean Sea. A total of 296 phytoplankton species and one subspecies belonging to 12 classes were identified from samples collected during the five seasonal cruises. The highest diversity was observed in the summer of 2015, with 204 species recorded, while the lowest was 137 species in the summer of 2016. Dinoflagellates dominated the species composition, accounting for 51% of the species, followed by diatoms (44%), and other groups (5%). At the genus level, Chaetoceros, Thalassiosira, Bacteriastrum, and Coscinodiscus were the most dominant diatom genus, whereas Protoperidinium, Tripos, Dinophysis, Oxytoxum, and Prorocentrum were dominant among dinoflagellates. Amphisolenia schauinslandii Lemmermann 1899 and Ceratoperidinium margalefii A.R. Loeblich III 1980 were recorded for the first time along the Turkish coast of the Aegean Sea. This study provides a comprehensive assessment of the phytoplankton taxonomic diversity in the region from to 2014-2016.

Phytoplankton species composition as bioindicator in the largest fragmented channel of the Pearl River, China.

To test the serial discontinuity concept (SDC) predictions in a regulated river ecosystem, environmental parameters and phytoplankton community structure were determined in a subtropical river (China) which was regulated by 11 cascade dams. Our results showed that total phosphorus (TP) and silicate during the wet period in several dams supported the SDC predictions. Variations of phytoplankton species composition in several cascade dams, such as Datengxia (DTX) and Changzhou (CZ), also supported the SDC predictions. Moreover, the stations near the dams showed the maximum or minimum values of total species numbers in each cascade segment. Predictive model indicated that the types of phytoplankton decreased in the middle reaches, conforming to SDC predictions. In the whole system of cascading dams, an increase in silicate concentration and phytoplankton communities in the downstream was also consistent with SDC predictions. Therefore, these findings aligned with the SDC predictions in the aspects of both single dam and whole cascade dam system to some extent. In future research, our aim is to further investigate the effects of cascade damming on additional phytoplankton-related indices in this aquatic ecosystem. We hope to gather more comprehensive data to fully validate the SDC predictions.

Joint seasonal dynamics of phytoplankton and zooplankton in the sub-Arctic White Sea

The seasonal succession of phytoplankton species composition and biomass plays a pivotal role in driving the seasonal variations in zooplankton community structure and biomass. Our study focused on the seasonal dynamics of planktonic communities in the Chupa Inlet (Kandalaksha Bay, White Sea) to determine if there are distinct complexes of phyto- and mesozooplankton species associated with different seasons, and whether these complexes are interconnected. Four seasonal groups of phyto- and zooplankton samples were revealed, each characterized by a specific composition of typical species. The winter and spring groups of phytoplankton and zooplankton corresponded to each other in their temporal span. Later in the year, this temporal correspondence was disrupted as early copepodite stages of Calanus glacialis dominated the community briefly in late spring, forming the basis of a separate seasonal group. From July until the end of the study period, warmer-water species constituted the community core, shaping the summer-autumn seasonal group. The role of smaller species in both phyto- and zooplankton communities increased during summer and autumn. The size structure and motility of the phytoplankton were found to significantly influence the seasonal succession of the zooplankton. This apparently contributes to better trophic coupling between phyto- and zooplankton throughout the seasonal cycle.

Biomonitoring of the surface waters of the Volyntsevo reservoir using the fluorimetry method

The article examines the state of the drinking Volyntsevo reservoir and its tributaries in conditions of significant changes in the hydraulic regime and pollution by waste mine waters. The state of algoflora of a water body is considered, the results of studying the species composition of phytoplankton, the content of basic photopigments and photosynthetic activity of microalgae are presented. The study presents the results of the application of the method of fluorimetric assessment of the state of phytoplankton cells as the main bioindicator of the state of the aquatic environment. The research was conducted in the vicinity of Yenakievo for the Volyntsevo reservoir and the Bulavin river. These water bodies are subject to significant man-made impacts: as a result of intensive water use of reservoir resources, there has been a significant decrease in water levels and, as a result, a deterioration in water quality. The conducted studies have shown a significant excess of the permissible standards for the content of magnesium ions, sulfates, total hardness and alkalinity in water samples. The negative impact of surface water pollution on the species composition of algoflora, as well as the photosynthetic activity of phytoplankton cells, has been shown. The obtained materials can serve as a basis for further monitoring of drinking reservoirs in the region. The current situation requires constant monitoring observations aimed at identifying and eliminating all sources of pollution of the studied water bodies.

Temporal phytoplankton dynamics and environmental variables in four Ethiopian soda lakes

We investigated the spatio-temporal dynamics of phytoplankton composition, chlorophyll-a as a proxy for algal biomass, and abundance in relation to environmental parameters in four Ethiopian soda lakes: Arenguade, Beseka, Chittu, and Shala. Triplicate water samples were collected from each lake from January to December 2020, four times in different seasons. Lake Chittu had the highest chlorophyll-a concentration, followed by Lake Arenguade, Beseka and Shala. Chlorophyll-a concentrations generally increased during the post rainy and dry season. The results of LR models are high for lakes Arengude, Beseka and Chittu. Lakes Shala and Beseka had the highest number of phytoplankton taxa, with both taxa composition and abundance dominated by Bacillariophyceae. Cyanoprokaryota, particularly Limnospira fusiformis, predominated in the abundance of Lakes Arenguade and Chittu. Water temperature, Secchi depth, turbidity, electrical conductivity, soluble reactive phosphorus, nitrate and silica significantly influenced the phytoplankton community structure. Long-term trend analysis revealed changes in phytoplankton biomass and lake taxonomic composition. The alteration in phytoplankton biomass and species composition of the lakes could be attributed to three factors: (1) frequent high-velocity explosions conducted for seismological studies in the past. This impact caused a dramatic increase in lake level in the case of Lake Beseka leading to a drop in nutrient concentration; (2) climate change and (3) salt content. Overall, our findings suggest that phytoplankton composition, biomass, and abundance varied according to seasonal fluctuations, emphasizing the possible effects of anthropogenic and natural causes on their community structure.

Features of Fluorescence Profiles and Species Composition of Phytoplankton in the Black Sea and the Sea of Azov

The aim of this work was to study the properties of vertical fluorescence intensity (FI) profiles of phytoplankton pigments (chlorophyll-a, phycocyanin, phycoerythrin, and beta-carotene) using data on the phytoplankton species composition obtained during the cruise 114 of the R/V ‘Professor Vodyanitsky’. The analysis of covariance matrices of phytoplankton pigment FI profiles in the upper 50-meter layer of the Black Sea indicates that the pigment composition of phytoplankton changes with depth, which may be associated with changes in its species composition. At the same time, 80 % variability of phytoplankton pigment FI profiles in the upper 20-meter layer is described by the first eigenvector. It agrees well with direct observations of the phytoplankton species composition, indicating the dominance of one phytoplankton division in the 20-meter layer. In addition, there are regional peculiarities: for example, the average FI values of the phytoplankton pigments in the Sea of Azov are significantly higher than those in the Black Sea, which is associated with a higher concentration of phytoplankton in the Sea of Azov.

Spring phytoplankton of Lake Onego as a trophic resource for deep-water benthos

In the past few years the relict deep-water crustacean Monoporeia affinis (Lindström, 1855) has become less abundant in Lake Onego, Europe’s second largest lake. Further studies are needed, therefore, to better understand the formation of spring phytoplankton as food for deep-water benthos. The aim of the present project was to study the temperature-dependent vertical distribution of phytoplankton in Petrozavodsk Bay of Lake Onego in the spring season. In May 2019, the total abundance, biomass and species composition of phytoplankton were assessed. The transparency and temperature of Onego water were also measured. The median values of phytoplankton’s total abundance and biomass at various growth stages were 1.15–1.67 M cells/l and 1.96–3.12 mg/l, respectively. The above indices were consistent with the long-term maximum growth of phytoplankton in Petrozavodsk Bay in spring and were not markedly different (p<0.05) from those for spring phytoplankton in 1989-2015, indicating the permanent trophic status of Petrozavodsk Bay in the spring season over the past 30 years. A significant difference (p>0.05) in the vertical distribution of phytoplankton, dominated by Aulacoseira islandica (O. Müll.) Sim diatoms, was found between the stations in May 2019. The reproduction of the relict deep-water crustacean M. affinis, taking place simultaneously with the intensive vegetation and the settling of its major food resource, A. islandica, on the bottom, suggests the formation of favourable feeding conditions for deep-water benthos in Petrozavodsk Bay of Lake Onego.

Состав и структура фитопланктона Сылвенско-Чусовского плеса Камского водохранилища (Россия)

Based on the materials from studies of phytoplankton in the SylvenskoChusovsky reach of the Kama Reservoir in July 2020 and 2022, its taxonomic composition, ecological-geographical structure and quantitative indicators were studied. The large marginal Sylvensko-Chusovsky reach of the Kama Reservoir is formed by the confluence of the Sylva and Chusovaya rivers and includes two districts and three sections (See Fig. 1). The mineralization of water throughout the reach varies significantly, from 225 to 1000 mgL-1, which is associated with the influx of river water. In the Sylva River, the average mineralization values in summer are significantly higher (650 mgL-1) than those of the Chusovaya River (250 mgL-1). Precipitation and surface inflow volumes in the study area (July 2020 and 2022) were below long-term averages. The years of research varied significantly in temperature regime: the water temperature of the Sylvensko-Chusovsky reach in 2020 was 30.3 ± 1.6°С, in 2022 – 20.3 ± 0.6°С. As a result of the study, 267 species and intraspecific taxa of algae from 9 departments were identified in the phytoplankton composition of the Sylvensko-Chusovsky reach of the Kama Reservoir. The basis of the species richness was formed by diatoms (36.0%), green (28.5%), golden (12.5%) algae, and cyanoprokaryotes (11.6%); the share of other algae departments totaled 11% (See Table 1). The species composition of phytoplankton differs in various parts of the reach, which is associated with the flow of river waters from the Sylva and Chusovaya rivers into the bays; the degree of floristic similarity according to the Sørensen-Chekanovsky coefficients is low and ranges from 0.41 to 0.68 (See Fig. 2). As a result of the carried-out work, the floristic list of algae of the Sylvensky Bay was replenished by 41%, previously numbering 69 species and varieties from 5 departments (See Fig. 3). In the ecological and geographical aspect, the algal flora of plankton is represented by typically planktonic species, widespread in water bodies of the globe, indifferent to water salinity, living only in fresh water bodies and preferring neutral waters (See Table 2). In Sylvensky Bay, the ecological structure of algocenoses retained its proportions from 2004 to 2022. During the summer low-water period of algal flora, the most significant contribution is made by cyanoprokaryotes, which appear with diatoms and green sea waves (See Fig. 4). Quantitative indicators of phytoplankton development varied significantly: abundance from 0.9 to 85.0 million cellsL-1, biomass from 0.39 to 13.02 mgL-1. Differences in the temperature regime during the years of the study determined the level of phytoplankton development; in 2022, the abundance and biomass values were three times higher compared to the abnormally hot 2020 (See Table 3). Throughout the entire water area, the dominant complex in number is represented mainly by species indicators of anthropogenic eutrophication (Aphanizomenon flos-aquaе, Aphanocapsa holsatica, Aulacoseira granulata, Stephanodiscus binderanus) and there is a massive development of non-heterocyst cyanoprokaryotes (Aphanocapsa holsatica, A. inserta, Anathece clathrata, Planktolyngbya limnetica, A. phanothece bachmannii). Dinophyte algae (Apocalathium aciculiferum, Peridinium cinctum, P. willei, Peridinium sp. and Gymnodinium sp.) played a significant role in the composition of dominant species by biomass, along with diatoms (See Table 4). As a result of the development of smallsized algal species, phytoplankton abundance values have increased more than 20-fold from 2004 to the present, while phytoplankton biomass has increased only twofold. The Shannon species diversity index values (2.96-5.02) indicate a complex structure and high biodiversity of phytoplankton. Higher index values were characteristic of riparian areas in 2022. Simpson's indices, reflecting the degree of expression of dominance of certain species, vary from 0.04 to 0.36 in the Sylvensko-Chusovsky Bay. The decrease of the index in the Chusovsky Bay (0.15 ± 0.03) is associated with a higher diversity of phytoplankton compared to the Sylvensky Bay (0.23 ± 0.05). Based on the composition of structure-forming species and the level of biomass, the trophic status of the Sylvensko-Chusovsky reach is determined as mesotrophic. Since the distribution of phytoplankton across the water area is uneven, the trophic state was assessed from β-oligotrophic in the Sylvensko-Chusovsky area to mesotrophic in the bays in 2020, and from mesotrophic to α-eutrophic level in 2022. The main changes in phytoplankton include a significant increase in the taxonomic diversity of golden algae, an increase in the coenotic role of disazotrophic cyanoprokaryotes and dinophyte algae, which indicates the progressive eutrophication of the waters of the Sylvensko-Chusovsky reach under the combined influence of anthropogenic factors and climate warming.

СТРУКТУРА ВИДОВОГО СОСТАВА СООБЩЕСТВ ФИТОПЛАНКТОНА МАНГРОВЫХ ЭКОСИСТЕМ В ПРИБРЕЖНОЙ ТЕРРИТОРИИ КХАНЬХОА ВЬЕТНАМА

The article presents the results of a study assessing the species diversity and structure of the species composition of phytoplankton communities in the mangrove ecosystems of Dambay, Nha Phu and Tuan Le in Khanh Hoa province. According to the results of the study, 202 species belonging to 199 genus, 69 families and 8 phylum were noted. Among them, phytoplankton species belonging to the Bacillariophyta department dominate, with a total of 149 species belonging to 83 genus, 42 families, which is 74% of the total number of species found. The second place is occupied by the department Miozoa, numbering 31 species belonging to 12 genus and 11 families, which is 15% of the total number of species found. The phylum Euglenozoa, Ochrophyta, Cercozoa and Chlorophyta have a small number of species, only 1-2 species, and are found only in some areas at a particular time of sampling. The structure of the phytoplankton species composition in the three study areas is not very similar. In the mangrove area, Nha Phu has the highest species diversity with 149 species; further follows in the territory of the Dam Bay mangroves, numbering 131 species; and the lowest is in the Tuan Le mangrove area, where there are 101 species. This can be explained by the difference in natural and social conditions of all three study areas.