Phytoplankton Parameters Research Articles

Phytoplankton morphological traits and biomass outline community dynamics in a coastal ecosystem (Gulf of Trieste, Adriatic Sea)

AbstractTrait-based ecology has recently gained increasing importance in phytoplankton research. In particular, the taxonomic and morphological traits, such as size and shape of phytoplankton cells, can help to unveil the ecological processes and their drivers in the pelagic domain. Our study aims to shed light on the trophodynamics of phytoplankton communities in a coastal ecosystem in the northern Adriatic Sea (Gulf of Trieste) using data on individual traits such as biomass, size and shape of phytoplankton taxa during a one-year study. The phytoplankton parameters were investigated at the levels of the whole community, groups, and individual cells, analysing also the probability distributions of biomass and size of the latter level. The results showed good agreement between abundance and biomass data, as well as individual size and biomass with differences partly explained by cell shapes. We have emphasized the role of the local freshwater source in bottom-up control, alternating with top-down control of phytoplankton dynamics through taxonomic and morphological diversity. The predominant bimodal and non-power law distribution, especially during and around the biomass peaks, confirmed the importance of nano- and microphytoplankton size classes and the role of blooms in destabilizing the trophic webs. We suggest that the analyses of distribution types of individual cell size and biomass can be appropriate to spot ecological processes driving to unconstrained phytoplankton proliferation or to periods of trophic web stability.

WATERHYPERNET: a prototype network of automated in situ measurements of hyperspectral water reflectance for satellite validation and water quality monitoring

This paper describes a prototype network of automated in situ measurements of hyperspectral water reflectance suitable for satellite validation and water quality monitoring. Radiometric validation of satellite-derived water reflectance is essential to ensure that only reliable data, e.g., for estimating water quality parameters such as chlorophyll a concentration, reach end-users. Analysis of the differences between satellite and in situ water reflectance measurements, particularly unmasked outliers, can provide recommendations on where satellite data processing algorithms need to be improved. In a massively multi-mission context, including Newspace constellations, hyperspectral missions and missions with broad spectral bands not designed for “water colour”, the advantage of hyperspectral over multispectral in situ measurements is clear. Two hyperspectral measurement systems, PANTHYR (based on the mature TRIOS/RAMSES radiometer) and HYPSTAR® (a newly designed radiometer), have been integrated here in the WATERHYPERNET network with SI-traceable calibration and characterisation. The systems have common data acquisition protocol, data processing and quality control. The choice of validation site and viewing geometry and installation considerations are described in detail. Three demonstration cases are described: 1. PANTHYR data from two sites are used to validate Sentinel-2/MSI (A&B); 2. HYPSTAR® data at six sites are used to validate Sentinel-3/OLCI (A&B); 3. PANTHYR and HYPSTAR® data in Belgian North Sea waters are used to monitor phytoplankton parameters, including Phaeocystis globosa, over two 5 month periods. Conclusion are drawn regarding the quality of Sentinel-2/MSI and Sentinel-3/OLCI data, including indications where improvements could be made. For example, a positive bias (mean difference) is found for ACOLITE_DSF processing of Sentinel-2 in clear waters (Acqua Alta) and clues are provided on how to improve this processing. The utility of these in situ measurements, even without accompanying hyperspectral satellite data, is demonstrated for phytoplankton monitoring. The future evolution of the WATERHYPERNET network is outlined, including geographical expansion, improvements to hardware reliability and to the measurement method (including uncertainty estimation) and plans for daily distribution of near real-time data.

Long-Term Dynamics of Phytoplankton Parameters and Water Temperature in the Area of Sevastopol (Black Sea)

Long-Term Dynamics of Phytoplankton Parameters and Water Temperature in the Area of Sevastopol (Black Sea)

Environmental factors controlling seasonal and spatial variability of zooplankton in thermokarst lakes along a permafrost gradient of Western Siberia

Humic thermokarst lakes of permafrost peatlands in Western Siberia Lowland (WSL) are major environmental controllers of carbon and nutrient storage in inland waters and greenhouse gases emissions to the atmosphere in the subarctic. In contrast to sizable former research devoted to hydrochemical and hydrobiological (phytoplankton) composition, zooplankton communities of these thermokarst lakes and thaw ponds remain poorly understood, especially along the latitudinal gradient, which is a perfect predictor of permafrost zones. To fill this gap, 69 thermokarst lakes of the WSL were sampled using unprecedented spatial coverage, from continuous to sporadic permafrost zone, in order to assess zooplankton (Cladocera, Copepoda, Rotifera) diversity and abundance across three main open water physiological seasons (spring, summer and autumn). We aimed at assessing the relationship of environmental factors (water column hydrochemistry, nutrients, and phytoplankton parameters) with the abundance and diversity of zooplankton. A total of 74 zooplankton species and taxa were detected, with an average eight taxa per lake/pond. Species richness increased towards the north and reached the maximum in the continuous permafrost zone with 13 species found in this zone only. In contrast, the number of species per waterbody decreased towards the north, which was mainly associated with a decrease in the number of cladocerans. Abundance and diversity of specific zooplankton groups strongly varied across the seasons and permafrost zones. Among the main environmental controllers, Redundancy Analysis revealed that water temperature, lake area, depth, pH, Dissolved Inorganic and Organic Carbon and CO2 concentrations were closely related to zooplankton abundance. Cladocerans were positively related to water temperature during all seasons. Copepods were positively related to depth and lake water pH in all seasons. Rotifers were related to different factors in each season, but were most strongly associated with DOC, depth, CH4, phytoplankton and cladoceran abundance. Under climate warming scenario, considering water temperature increase and permafrost boundary shift northward, one can expect an increase in the diversity and abundance of cladocerans towards the north which can lead to partial disappearance of copepods, especially rare calanoid species.

Evaluation of three contrasting models in estimating primary production from ocean color remote sensing using long-term time-series data at oceanic and coastal sites

Accurate estimates of depth-integrated Net Primary Production (NPP, mg C m−2 d−1) and the creation of a robust climate data record of NPP for the global oceans are essential goals of the ocean color remote sensing community. Here, we take advantage of in situ NPP measurements from three long-term time-series sites, the HOT (Hawaii Ocean Time-series), BATS (Bermuda Atlantic Time-series Study) and CARIACO (Ocean Time-Series Program from the Cariaco basin), spanning over 30 years to evaluate three contrasting models in estimating NPP from ocean color remote sensing. These models for NPP estimation include the Absorption-based Model (AbPM), which relies on phytoplankton absorption coefficient, the Vertically Generalized Production Model (VGPM), which centers on chlorophyll-a concentration, and the Carbon-based Productivity Model (CbPM) centering on phytoplankton carbon. In addition to the accuracy of NPP estimation from these models, we laid great emphasis on evaluating their skills in capturing the monthly to seasonal variations and interannual trends in NPP at the three sites. Comparison with in situ NPP at all three long-term sites (∼20 years) showed that AbPM yielded the highest coefficient of determination (R2 = 0.67) and the lowest uncertainties (Bias = 0.03 and unbiased root mean square difference = 0.17). Seasonal and interannual variations apparent in the in situ NPP time-series records were best captured by AbPM. These results showcase the robust capabilities of AbPM and its superiority for global carbon cycling and climate change studies, largely because it takes into account optical and photosynthetic parameters of local phytoplankton.

INFLUENCE OF ATMOSPHERIC PRECIPITATION AND SURFACE RUNOFF ON PHYTOPLANKTON CHARACTERISTICS IN THE NORTHERN PART OF THE BLACK SEA

The joint dynamics of the Black Sea phytoplankton parameters (primary production, specific growth rate, biomass) and the amount of precipitation over the period from 1998 to 2015 was studied in coastal areas and the open coast of the northern part of the Black Sea. The analysis used satellite data (SG) (GPCPMON) GPCP Version 3.2, TRMM TMPA (3B42RT), as well as SeaWiFS from 1998 to 2010, MODIS-Aqua from 2002 to 2015 and MODIS-Terra from 2000 to 2015. Phytoplankton indicators were calculated according to 46 КОВАЛЕВА, СУСЛИН LOMONOSOV GEOGRAPHY JOURNAL. 2023. VOL. 78. NO. 4 the models developed earlier by the authors. The average monthly values of all considered values were evaluated, as well as bi-weekly and daily values for atmospheric precipitation. As a result of the study, it was revealed that the role of atmospheric precipitation for the variability of phytoplankton characteristics is not significant in vast water areas over long time intervals, and it could be neglected. In some cases in the presence of large rivers and coastal runoff it increases up to 30% in the offshore areas. There was also a more noticeable effect of atmospheric precipitation on the biological productivity of phytoplankton in small, limited water areas over short time intervals. According to our data during the 18-year period there was a more noticeable correlation between the specific growth rate and precipitation in winter than in other seasons for the open coast of the Black Sea. The correlation of biomass and primary production with atmospheric precipitation is less pronounced. The specific growth rate correlated more than other studied phytoplankton indicators with the amount of precipitation. In three districts, an increase in the amount of precipitation relative to the previous level with monthly averages above 0,6 mm/day led to an increase in the specific growth rate, or maintained it at the same level. The increase in the specific growth rate was not the same everywhere and was not proportional to the amount of atmospheric precipitation. This indicates the influence of many factors on phytoplankton characteristics; however, precipitation could have an additional stimulating role.

An evaluation of long-term physical and hydrochemical measurements at the Sylt Roads Marine Observatory (1973–2019), Wadden Sea, North Sea

Abstract. The Sylt Roads pelagic time series covers physical and hydrochemical parameters at five neighboring stations in the Sylt–Rømø bight, Wadden Sea, North Sea. Since the beginning of the time series in 1973, sea surface temperature (SST), salinity, ammonium, nitrite, nitrate, and soluble reactive phosphorus (SRP) have been measured twice a week. The other parameters were introduced later (dissolved silicate (Si) since 1974, pH since 1979, dissolved organic nitrogen (DON) since 1996, dissolved organic phosphorus (DOP) since 2001, chlorophyll a since 1979, and suspended particulate matter (SPM) since 1975), and in the case of dissolved oxygen, were already discontinued (1979–1983). In the years 1977, 1978, and 1983, no sampling took place. Since the start of the continuous sampling in 1984, the sea surface temperature in the bight has risen by +1.11 ∘C, with the highest increases during the autumn months, while the pH and salinity decreased by 0.23 and 0.33 units, respectively. Summer and autumn salinities are generally significantly elevated compared to spring and winter conditions. Dissolved nutrients (ammonium, nitrite, nitrate, and SRP) have displayed periods of intense eutrophication (1973–1998) and de-eutrophication since 1999. Silicate has shown significantly higher winter levels since 1999. Interestingly, phytoplankton parameters did not mirror these large changes in nutrient concentrations, as a seasonal comparison of the two eutrophication periods showed no significant differences with regard to chlorophyll a. This phenomenon might be triggered by an important switch in nutrient limitation during the time series. With regard to nutrients, the phytoplankton was probably primarily limited by silicate until 1998, while, since 1999, the SRP limitation has become increasingly important. All data are available in Rick et al. (2017b–e, 2020a–o) from https://doi.org/10.1594/PANGAEA.150032, https://doi.org/10.1594/PANGAEA.873549, https://doi.org/10.1594/PANGAEA.873545, https://doi.org/10.1594/PANGAEA.873547, https://doi.org/10.1594/PANGAEA.918018, https://doi.org/10.1594/PANGAEA.918032, https://doi.org/10.1594/PANGAEA.918027, https://doi.org/10.1594/PANGAEA.918023, https://doi.org/10.1594/PANGAEA.918033, https://doi.org/10.1594/PANGAEA.918028, https://doi.org/10.1594/PANGAEA.918024, https://doi.org/10.1594/PANGAEA.918034, https://doi.org/10.1594/PANGAEA.918029, https://doi.org/10.1594/PANGAEA.918025, https://doi.org/10.1594/PANGAEA.918035, https://doi.org/10.1594/PANGAEA.918030, https://doi.org/10.1594/PANGAEA.918026, https://doi.org/10.1594/PANGAEA.918036, and https://doi.org/10.1594/PANGAEA.918031.

Acclimation by diverse phytoplankton species determines oceanic carbon to nitrogen ratios

AbstractThe carbon to nitrogen (CN) ratio of phytoplankton connects the carbon and nitrogen cycles in the ocean. Any variation in this ratio under climate change will alter the amount of carbon fixed by photosynthesis, and ultimately the amount sequestered in the ocean. However, a consistent mechanistic explanation remains lacking for observed species‐specific variations in phytoplankton CN ratios. We show that acclimation to ambient environmental conditions explains the observed variation of phytoplankton CN ratios by incorporating phytoplankton acclimation theory based on a resource allocation trade‐off between carbon vs. nitrogen acquisition capacity into a three‐dimensional marine ecosystem model. Inter‐specific differences in CN ratio and its sensitivity are caused by inter‐specific differences in Droop's minimum nitrogen cell quota. Our model, constrained by observed phytoplankton parameters, shows that the global mean phytoplankton CN ratio is greater than the canonical Redfield ratio, as suggested previously based on regional in situ observations.

Evaluation of Mangrove Water Quality in Pancer Cengkrong, Trenggalek and Sine, Tulungagung, East Java, Indonesia Using Phytoplankton as Bioindicators

Highlight Research Anthropogenic factors are the main cause of damage to mangrove ecosystems Restoration is a method for ecosystem restoration Restoration success is seen from the physical, chemical, and biological parameters Phytoplankton is a bioindicator of water quality The abundance of mangroves can explain the state of an ecosystem Abstract Mangrove ecosystems in Sine and Pancer Cengkrong had degraded due to land-use change and restoration has been carried out over a few year on the damaged location. This study was conducted to evaluate water quality of mangrove ecosystems at both locations based on physical, chemical and phytoplankton parameters as bioindicators. The evaluation of Cengkrong Mangrove was carried out at 4 different locations based on different periode of restoration, namely restoration of 2008-2009, 2013-2014, natural mangroves, and 2005 succession mangroves, whereas there was only one sampling site at Sine mangrove namely 1998-2008 restoration. The physico-chemical parameters measured include water temperature, air temperature, conductivity, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), salinity, nitrate, and orthophosphate. Phytoplankton data was used to measure, trophic diatom index (TDI) as an indicator of water nutrition status, and pollution tolerant value (%PTV) as an indicator of organic pollution. The results showed that the water quality at all the study locations met the Indonesian Ministry of Environment Regulation No 51/2004, except nitrate and phosphate. Based on the TDI index, mangrove in Sine, Cengkrong 2013-2014 restoration, and 2005 succession mangroves were categorized as hyper-eutrophic, natural Cengkrong mangroves were categorized as eutrophic, and 2008-2009 restored Cengkrong mangroves were categorized as meso-eutrophic. Based on the %PTV index, in the Sine mangrove, 2013-2014 Cengkrong restoration, and 2005 succession mangroves were classified as high levels of organic matter pollution, while in the Cengkrong 2008-2009 restoration and natural Cengkrong were classified as a moderate level of organic pollution.

Identification and determination of optimum growth condition with respect to selected environmental parameters for open sea cultivation of Gracillaria edulis in Andaman water

Gracilaria edulis is one of India's most widely cultivated seaweeds. Pilot scale cultivation of Gracilaria edulis was initiated at Andaman, India for the first time. In the present study attempt has been made to identify how different water quality parameters influence the growth. Total 11 physicochemical parameters and 9 microbiological parameters, as well as chlorophyll and zooplankton, phytoplankton parameters were studied for two different seasons to evaluate which parameters influence seaweed growth. Six (nitrate, nitrite, ammonia, silicate, chlorophyll, photosynthetic active radiation) have a positive impact on seaweed growth, while some of the bacterial species showed negative impact. Lowess 3D curve fit model showed pH range from 7.59 to 7.82, N/P ratio of 2.046, rainfall 23.85–24 mm, and Photosynthetic active radiation of 376.6 W/m2 are optimum for Gracillaria growth. This model can be applied to future mass culture.

Noctiluca Scintillans Distribution Largely Regulated by Phytoplankton Biomass in the East China Sea and Southern Yellow Sea

Noctiluca scintillans feeds on a large number of phytoplankton, including diatoms and dinoflagellates, and frequently forms a red tide in the East China Sea (ECS) and southern Yellow Sea (SYS). However, the spatiotemporal distribution pattern, controlling factors, and long-term change of N. scintillans in the ECS and SYS remain unclear. In the present study, we collected N. scintillans samples from the ECS and SYS throughout the four seasons of 2011. We sampled phytoplankton and environmental parameters simultaneously. The depth-integrated abundance (DIA) of N. scintillans was the highest and lowest in summer and winter, respectively. N. scintillans is distributed abundantly in eutrophic coastal waters and the Changjiang Estuary, which are characterized by high concentrations of phytoplankton and chlorophyll-a. A Spearman correlation test demonstrated that its DIA in the upper 30-m water column was generally more significantly associated with phytoplankton abundance and chlorophyll-a concentration than with temperature and salinity. The results of the generalized additive models revealed that chlorophyll-a concentration explained more of the variation in N. scintillans abundance than temperature and salinity throughout the year, particularly in warm seasons. These findings indicate that the seasonal and spatial changes of N. scintillans are largely regulated by phytoplankton biomass. Compared with the historical data from 1959 and 2002, the abundance of N. scintillans in the Changjiang Estuary increased considerably in 2011 with increasing phytoplankton abundance resulting from accelerated eutrophication and warming. These results clarify the controlling factors, red-tide formation mechanism, and changing trends associated with the N. scintillans in the ECS and SYS.

Особливості формування й функціонування фітопланктону малих водосховищ

Regularities of phytoplankton formation and functioning of small reservoirs are established. <i>Chlorophyta</i> (32.7% of the total list of species) and <i>Bacillariophyta</i> (24.6%) were found to be predominant in species richness. Cyanobacteria species have been found to increase as the area and volume of reservoirs increase, and <i>Euglenozoa</i> is ahead of them in smaller bodies of water. The main abiotic parameters that determine the changes in the structural parameters of phytoplankton of the studied reservoirs are determined. The main differences in the structural and functional characteristics of phytoplankton of small reservoirs built on Polissya rivers in comparison with large Dnieper and Volga ones have been clarified.

Community Structure of Eukaryotic Phytoplankton in Wetland of Golmud River and Its Lower Reaches and Relative Environmental Factors

Identification of the community structure of phytoplankton is an important link in studying the structure and function of aquatic ecosystems. However, research on the community structure of phytoplankton in the Golmud area is very scarce at present. To explore the composition of phytoplankton in the Golmud area, eukaryotic phytoplankton and environmental parameters were sampled in September 2020. The composition and diversity of the eukaryotic phytoplankton community were determined by microscopic observation and Illumina high-throughput sequencing technology. The results showed that a total of 40 species of eukaryotic phytoplankton from 4 phyla were identified by microscopic observation, and 154 species of eukaryotic phytoplankton from 7 phyla were obtained by high-throughput sequencing, mainly Bacillariophyta and Chlorophyta. The dominant species were Dunaliella sp., Teleaulax sp., Parvodinium mixtum, and Lindavia radiosa. The eukaryotic phytoplankton density in summer was 0.09–12.08 × 105 cells/L, the total biomass was 0.002–0.55 mg/L, and the concentration of chlorophyll-a was 0.00–0.91 μg/L. Multiple α diversity indices showed that the diversity of water in different salinities was in the order of freshwater > brackish > saline. The β diversity results showed that the eukaryotic phytoplankton community composition was more similar in water with the same salinity. The redundancy analysis results of water with different salinities showed that environmental factors susc as salinity, total phosphorus concentration, and dissolved oxygen affected the eukaryotic phytoplankton community structure, among which salinity had the greatest influence.

Preliminary Assessment of Ecological Status of the Siversky Donets River Basin (Ukraine) Based on Phytoplankton Parameters and Its Verification by Other Biological Data

The river basin of Siversky Donets is of great scientific interest since this river runs through a territory with heavy industry (in particular, coal mining, chemical processing and metal industries). Within the basin, rivers of different sizes were explored (small, medium, large and extra-large) that flow through siliceous and calcareous rocks on the same elevation (lowland—below 200 m a.s.l.). Phytoplankton, as one of the Biological Quality Element, was used to perform the assessment of ecological status of the water bodies within the Siversky Donets river basin in 2019. The state monitoring program based on the updated approaches has been implemented in the river basin for the first time. The composition of phytoplankton species in the basin comprised 167 species (168 intraspecies taxa), mainly Bacillariophyta (63%) and Chlorophyta (22%) with the presence of other species (Cyanobacteria, Charophyta, Chrysophyta, Dinophyta and Euglenophyta). High species diversity and divisions amount are a distinctive property of the smaller rivers, while the bigger rivers show lower number of divisions. The “bloom” events, which are important ecological factors, were not detected in the Siversky Donets river basin. Algal species composition in plankton samples of the basin was identified and series of ecological parameters, such as habitat preferences, temperature, pH, salinity, oxygenation and organic water pollution according to Watanabe and Sládeček’s index of saprobity (S) trophic state and nitrogen uptake metabolism were analyzed. The ecological conclusions were also verified by a canonical correspondence analysis (CCA). The significance of the Canonical Correspondence Analysis (CCA) results was estimated of by a Monte-Carlo permutation test. The high concentrations of inorganic phosphorus compounds (permanganate index (CODMn)) and nitrite ions favored the diversity of Chlorophyta and Cyanobacteria diversity correlated with the levels of bicarbonate and CODMn. High diversity of diatoms was facilitated by the total amount of dissolved solids and chemical oxygen demand (COD). It was found that low water quality could be associated with conditions leading to predominant growth of the mentioned groups of algae. According to the analysis, the highest water quality was characterized by balanced phytoplankton composition and optimal values of the environmental variables. The sites with reference conditions are proposed for future monitoring.

A modelling approach to simulate Chlorophyta and Cyanobacteria biomasses based on historical data of a Brazilian urban reservoir

A process-based model was used to simulate a hindcast based on the worst historical water quality condition of a tropical urban reservoir. Paranoá Lake is located in Brasília-DF, Brazil, and went through intense eutrophication in the 70s and 90s, with an important cyanobacterial bloom event in 1978. The parameters of phytoplankton were calibrated, focusing on the group of Chlorophyta (green algae) and Cyanobacteria (blue-green algae) at four depths (1, 10, 15 and 20m). The results indicated that the model was able to reproduce the Cyanobacteria biomass in comparison with the observations (RMSE=22-29.10-3 mgC L-1). On the other hand, the simulated Chlorophyta biomass showed good agreement with the observed data only in the bottom layer (RMSE=29. 10-3 mgC L-1 at 20m). In the hindcast simulation, the model was able to predict a significant increase in cyanobacterial biomass facing a water quality deterioration. In the meantime, the simulated Chlorophyta biomass decreased, which may indicate the phytoplankton group succession in response to the environmental conditions.

Hydrobiological and ichthyological features of the Shirokovsky Reservoir

The characteristic of Shirokovsky Reservoir by communities of phytoplankton, zooplankton, benthic invertebrates, and fish is given. It is the first investigation of the reservoir since the building time of 1948. All levels of the ecosystem are impoverished as species compositions as functional groups. A considerable part of all communities is presented by riverine oxyphilous species. Any invasion species of algae, invertebrates, and fish haven’t registered. The maximal species richness and quantitative parameters of phytoplankton have been registered in the upper riverine part of the reservoir and were determined by Bacillariophyta (primarily centric species). The zooplankton complexes’ dominants were Bosmina longirostris, Daphnia galeata, and Mesocyclops leuckarti. Maximal quantity of zooplankton has been shown in the middle part of the waterbody. The species of oligochaetes Limnodrilus hoffmeisteri and chironomids Parakiefferiella coronata were the most important in benthic communities’ structure. Benthofauna species richness and quantity of benthic invertebrates have been maximal in the lower part of the reservoir. The most common fish species at the current period are dace, perch, and Siberian roach. The fish quantity has been the richest in the middle part of the reservoir with lots of shallow areas. Assessing the quantitative values, the Shirokovsky Reservoir was classified as an oligotrophic waterbody at present.

The State of the Planktonic and Benthic Components of the Ecosystem of the Golden Horn Bay (Peter the Great Bay, Sea of Japan) in the Area of the Coal Terminal

Monitoring study of the state of the planktonic and benthic components of the ecosystem of the Golden Horn bay, Peter the Great Bay of the Sea of Japan in the area of the coal terminal was carried out in the autumn of 2020. Phytoplankton in the studied area was characterized by a depleted species composition. In September 2020, phytoplankton bloom was noted at the monitoring points, due to the massive development of diatom microalgae of the Chaethoceros genus, which accounted for 90% of the total phytoplankton. In November, the amount of phytoplankton was an order of magnitude lower, and the role of dinophytic algae increased in the community. Changes in the species composition and quantitative parameters of phytoplankton correspond to the seasonal dynamics in the eastern part of the Amursky bay, which is subject of anthropogenic pollution. Based on the study carried out, it can be concluded that the activities of the coal terminal in the Golden Horn bay had no effect on the structure of communities and, in general, there was no over-normative effect on the state of aquatic biological resources.

Assessment of the Trophic State of a Small Plain Reservoir during Different Periods of Its Existence (a Case Study of the Penza Reservoir on the Sura River)

The present study provides comparative characterization of the contents of nutrients and organic matter and quantitative parameters of phytoplankton of the Sura (Penza) reservoir during 1984–1992 and 2016–2019. At present, the content of phosphates has increased by 3 times while the concentration of mineral nitrogen has remained unchanged. The seasonal dynamics of phosphorus and mineral nitrogen are different: the maximum phosphate concentrations are observed in summer and autumn, but nitrogen is the highest during the flood period. At the present time, phosphorus is mainly generated in intra-reservoir processes. Nitrates were the predominant form of mineral nitrogen in 2016–2019, and their spring maximum suggests predominant intake with the flood flow. The ratio of the mineral forms of nitrogen and phosphorus indicates that, at the present time, phosphorus is not the element that limits the development of algae. In certain periods (summer 2017–2018), a significant negative relationship was observed between the algal biomass and the total iron content in water (r = -0.81, p = 0.016). No Cyanoprocaryota “blooms” have been observed in recent years. In 2019, the abundance of Cyanoprocaryota increased, but in some regions, biomass was no more than 2.18–2.42 mg/dm3. In 2019, the dominant Cyanoprocaryota group did not contain Microcystis aeruginosa (Kütz.), but a new species was identified – Planktothrix agardhii (Gom.) Anagn. et Kom., which is resistant to low light and the low nitrogen to phosphorus ratio. The proportion of readily oxidized organic matter in the total organic matter, both at the end of the 20th century and recently, characterizes the reservoir as stably eutrophic, although the quantitative characteristics of phytoplankton in recent years indicate declining trophic status

Phytoplankton of the delta of the Mekong River during the dry season

Human activity has disturbed the functioning of river ecosystems all around the globe. The current global climatic fluctuations and local anthropogenic impact lead to rearrangement in the structure and functioning of aquatic communities. One of the most important components of aquatic ecosystems is phytoplankton as the main primary producer of the organic matter, the basis for trophic relations and indicator of changes in the environment. This article presents the first results of a study concerning the peculiarities of quantitative distribution of biomass and species composition of phytoplankton in the delta of the Mekong River at the beginning of the dry season (December of 2018). Diatoms dominated according to biomass practically in all the stations of selection of samples. The total biomass of phytoplankton on average accounted for 0.049 ± 0.007 mg/L at the abundance of 40 ± 7 103 ind./L. In practically all the studied plots, according to biomass, the dominating diatoms were first of all Aulacoseira granulata, A. islandica, Cyclotella meneghiniana, Cyclotella spp., and Oxyneis binalis. Among Chlorophyta, most often we found Chlorella sp. and Scenedesmus quadricauda, but their biomass was insignificant. We determined statistically significant correlation relationships between biomass of phytoplankton and hydrological parameters. Based on the Spearman’s rank correlation coefficient, we determined negative relations between the total biomass of phytoplankton with salinity and pH. Positive correlation was seen between the biomass of diatoms and turbidity, and also between the temperature and the biomass of chlorophytes and Dinophyta. The biomass of golden algae (Chrysophyceae) and Dinophyta positively correlated with the mineralization. Quantitative regression analysis confirmed the close relationship between the total biomass of phytoplankton, hydrophysical and hydrochemical parameters. Besides the importance of scientific data on biological diversity and ecology of plankton algae, the results we obtained are necessary for organizing biological monitoring in the delta of the Mekong River in the future.

Influence of Temperature and Water Level on the Phytoplankton in the Estuarine Zone of the Rybinsk Reservoir Tributary

The structural parameters of phytoplankton in the estuarine region of a small tributary (Ild River) were studied in 2009–2011 and compared with the adjacent sections of the free-flowing section of the river and the pelagic zone of the Rybinsk Reservoir. Phytoplankton of the mouth estuarine region of the Ild River is characterized by high floristic and specific richness, biomass and coenotic diversity. With an increase in water temperature and a decrease in the water level in the reservoir, an increase in floristic richness, biomass, and the degree of similarity of the ratio of large taxonomic groups of algal communities of ecotone and border zones were observed in the mouth area of the tributary.