Phytoplankton Species Richness Research Articles

Phytoplankton Characteristics in Various Ecosystems of the Dnieper River: Abiotic Factors and Phytoplankton Taxonomic Diversity

The paper deals with comparative analysis of the main abiotic factors and phytoplankton taxonomic characteristics in various ecosystems of the Dnieper River, including the head cascade Kyiv Reservoir and the natural Dnieper estuary. Investigations were carried out in summer seasons of 2014-2020. The studied water bodies differ significantly in their physical, geographic, climatic, hydrological, and hydrochemical characteristics. However, they have some common features: both water bodies are large highly productive lentic ecosystems with similar morphometric parameters. As regards phytoplankton taxonomic diversity, the similarities include the same rank distribution of leading divisions and high species richness of summer phytoplankton. A number of differences has also been observed: a higher share of Bacillariophyta in the reservoir and higher shares of Cyanobacteria and Miozoa in the estuary; higher species richness of phytoplankton in the Dnieper estuary compared to the Kyiv Reservoir; a large number of species, occurring only in one of the studied ecosystems - 75 species in the Kyiv Reservoir and 88 species in the Dnieper estuary. The obtained data can serve as a background for assessing an adverse effect of the Russia's military aggression and arising hazards for the Dnieper ecosystems of Ukraine.

Scenarios of temporal environmental alterations and phytoplankton diversity in a changing bay in the East China Sea

In the context of global change, the stressors of warming and eutrophication have significant ecological implications in coastal waters. In order to examine the diversity of phytoplankton and its relationship with water quality, we conducted a survey of phytoplankton community compositions and their correlation with environmental changes over four seasons in a eutrophic bay located in the East China Sea. Through a systematic analysis, we identified diatoms and dinoflagellates as the primary dominant groups, with the species Skeletonema costatum, Skeletonema marinoi, Biddulphia sinensis, Thalassiosira eccentrica, Leptocylindrus danicus, Coscinodiscus oculus-iridis, Coscinodiscus jonesianus, and Chaetoceros knipowitschi as the most abundant species in all seasons. Significant seasonal alterations were observed in both environmental settings and phytoplankton species richness, dominance, and abundance. The phytoplankton community varied in its response to diverse aquatic environments and was principally affected by temperature, silicic acid concentrations, and suspended solids. Elevated temperatures were found to promote an increase in phytoplankton abundance. However, no clear evidence of diatom and dinoflagellate succession in relation to N:P ratio was observed across seasons. Water quality analysis illustrated that the majority of the study area exhibited a mid-eutrophic with severe organic pollution. The abundance of phytoplankton was significantly influenced by eutrophication and organic pollution. The accelerated warming process related to coastal nuclear power plants and nutrient regime alterations significantly affect the temporal shift of the phytoplankton community. These findings contribute valuable insights into the effects of eutrophic environments on the structure of phytoplankton communities in coastal aquatic systems.

Limnology of the Ndongo stream (South-West Cameroon): wastes management, water physicochemical quality and phytoplankton species richness

Freshwater ecosystems are subject to anthropogenic contaminants. This study aimed at assessing waste management stratagem by the local population and implications on water abiotic variables as well as phytoplankton species richness of the Ndongo stream, South-West Cameroon. For this purpose, 144 structured questionnaires were randomly administered to inhabitants around the stream to assess wastes management practices. Water and phytoplankton analysis was done in three selected sites. The mainstream of inhabitants (67%) dumped wastes in facilities provided by the Buea Council. The sorting of wastes before disposal was not common among respondents (72%). Recycling of wastes was done by only 37.8% of inhabitants. Half of the respondents (50.7%) claimed being ready to contribute financially for waste management while 81.2% said they were aware of the consequences of poor waste management. The main source of domestic water in the area was tap water (89.6%) and the Ndongo stream was mainly utilised for washing clothes (47.9%). Water abiotic variables that exhibited significant spatial trends included conductivity, TDS, velocity, width, depth and flow rate. There was no significant difference in the spatial distribution of temperature, pH, salinity and dissolved oxygen. The phytoplankton community was made of 36 species distributed in 37 families. Taxa such as Lynbya sp., Oscillatoria sp. and Closterium sp. were found in all the sampling sites, making them resident species of the stream. The sampling site at the lower course of the stream had the highest phytoplankton species richness. The highest algal pollution index was found in site 3at the lower course of the stream. Species richness had a positive and non-significant correlation with temperature, conductivity, TDS, salinity, velocity, depth and discharge. Water pH, dissolved oxygen and width had a negative and non-significant correlation with species richness. The local population should be educated on wastes management and its implications on the environment.

Таксономический состав и экологические особенности фитопланктона озера Островито (Псковская область)

Lake Ostrovito is located in the Pskov region and belongs to the basin of the Belyavitsa River, a tributary of the Velikaya River. The lake covers an area of 1.1 km2, with a maximum depth of 16.0 m and presents an important recreational and fishery facility in the Pskov region, constantly experiencing anthropogenic impact due to the close proximity of villages and recreation centers. Monitoring works have been conducted to assess the ecological state of this lake. The aim of the work was to study the species richness, quantitative characteristics and ecological features of phytoplankton of Lake Ostrovito in the autumn period of 2020. The study identified 65 species and intraspecific phytoplankton taxa from 7 phylums. The basis of the floral complex was made up of representatives of the departments Chlorophyta, Bacillariophyta and Cyanobacteria. The analysis of the floral similarity of phytoplankton communities of the studied lake stations using the Sierensen-Chekanovsky index showed their average degree of similarity (from 43.3 to 58.1%). The values of the abundance of autumn phytoplankton varied from 127 thousand cells/l to 488 thousand cells/l (the average number is about 290 thousand cells/l). Phytoplankton biomass ranged from 68.7-110 micrograms/l (average biomass – 96.1 micrograms/l). The average value of the Milius trophic index was 21.1, which indicates an oligotrophic type of reservoir. According to ecological and geographical analysis, freshwater widespread planktonic forms of microalgae predominated in Lake Ostrovito, preferring slightly alkaline waters and indicating moderate pollution of the reservoir.

Mechanistic Models of Trophic Interactions: Opportunities for Species Richness and Challenges for Modern Coexistence Theory.

AbstractMany potential mechanisms promote species coexistence, but we know little about their relative importance. To compare multiple mechanisms, we modeled a two-trophic planktonic food web based on mechanistic species interactions and empirically measured species traits. We simulated thousands of possible communities under realistic and altered interaction strengths to assess the relative importance of three potential drivers of phytoplankton and zooplankton species richness: resource-mediated coexistence mechanisms, predator-prey interactions, and trait trade-offs. Next, we computed niche and fitness differences of competing zooplankton to obtain a deeper understanding of how these mechanisms determine species richness. We found that predator-prey interactions were the most important driver of phytoplankton and zooplankton species richness and that large zooplankton fitness differences were associated with low species richness, but zooplankton niche differences were not associated with species richness. However, for many communities we could not apply modern coexistence theory to compute niche and fitness differences of zooplankton because of conceptual issues with the invasion growth rates arising from trophic interactions. We therefore need to expand modern coexistence theory to fully investigate multitrophic-level communities.

Physical Drivers of Monthly Variation in Phytoplankton Community in the Tidal Freshwater Zone of the Macrotidal Qiantang River Estuary, Eastern China: Implications for Reducing the Risk of Harmful Cyanobacterial Blooms

AbstractThe Qiantang river estuary flows into Hangzhou Bay, on the East China Sea, and has one of the largest tidal bores worldwide. The tidal freshwater zone (TFZ) in this shallow macrotidal estuary is subjected to strong riverine and marine forcings. We investigated monthly variation of phytoplankton and environmental drivers in the upper and lower sections of TFZ during 2016. Large numbers of phytoplankton taxa (422) and genera (161) were identified. Diatoms were dominant in most months, but cyanobacteria abundance reached its greatest in warm months when runoff was low. Surprisingly, relatively high dominances of marine diatom species (e.g., Cyclotella stylorum, Skeletonema, and Thalassiosira) were observed in the TFZ with salinities usually <1 PSU. Microcystis contributed up to 50% to phytoplankton abundance in the upper TFZ in September, consistent with upstream bloom events. Abundances of phytoplankton and cyanobacteria were significantly negatively correlated with monthly runoff and sediment fluxes. Generalized additive models suggested that variation in phytoplankton abundance was largely explained by river flow, temperature and nutrients. Phytoplankton community composition varied significantly across different months and sections. Redundancy analysis indicated that temperature and flow rate explained more variation in phytoplankton community than other variables, but nutrients, Secchi depth and salinity also contributed significantly to the explained variation. Variance partitioning analysis confirmed that phytoplankton variation was largely regulated by physical variables rather than nutrients. These findings highlight the unexpectedly great phytoplankton species richness, dominance of marine diatoms, and physical drivers in the eutrophic macrotidal TFZ under strong tidal forcing.

Effects of Water Stratification and Mixing on Plankton Community Structure in a Floating Solar Power Plant

Plankton community structure play pivotal roles in aquatic ecosystems, influencing their structure, function and services. However, little is known about the effects of water stratification and mixing on the dynamics of aquatic ecosystems. The influence of water stratification and mixing on plankton community structure was studied in the Floating Da Mi Solar Power Plant was done between March 2020 and September 2022, encompassing both dry and rainy seasons. Data from 4 sites were used as a representative example for the study area to conduct a qualitative study. To implement this assessment, the analyses were based on MRC methods and classifications, these improved by the scientific group. The results showed that 86 species of phytoplankton and 23 species of zooplankton were found in the study area. The density of phytoplankton at each site ranged from 279 to 32,282 individuals/sample, while the density of zooplankton at each site fluctuated from 5 to 33 individuals/sample. The calculated values for the diversity index (H’) of phytoplankton and zooplankton fluctuated from medium to quite high levels from 1.55 to 3.69; 1.562.95 respectively. The results also showed that several environmental variables, including temperature, dissolved oxygen, and chlorophyll-a were correlated with species richness, density and diversity index of phytoplankton and zooplankton. The obtained results will be useful for the monitoring of changes of aquatic ecosystem at the study area, in particular the sensitivity of aquatic flora and fauna to changes in environmental variables.

An analysis of interannual data on phytoplankton and zooplankton associations in fluctuating soda lakes

Aquatic ecosystems in arid regions are important and unique habitats for aquatic wildlife and support species biodiversity. Endorheic soda lakes in Central Asia are subject to great fluctuations in its size depending on climatic conditions. Here we present research results covering the last 20 years, including the period from the maximum filling of the Torey lakes (Transbaikalia, Russia) to their aridification and the initial phase of their refilling. Barun-Torey and Zun-Torey lakes are the largest soda lakes in the arid zone with a large water surface area. A unique feature of lakes is the unstable hydrological regime. The reason for the water level change is the periodic filling and drying of lakes due to cyclic climatic changes in humidity and temperature. We aim to determine the response of the plankton communities to environmental change in the Torey lakes over this period. We analysed the interannual variations in phytoplankton and zooplankton species richness, structure and density. We conducted our studies during various phases of the hydrological cycle, including three periods for Zun-Torey Lake (high (1999 and 2003), intermediate (2007, 2011) and low (2014 and 2016) lake levels) and two periods for Barun-Torey (high water level (1999 and 2003) and the initial filling phase (2014, 2016, 2018, 2020, 2021)). Barun-Torey Lake dried up completely in summer 2009 and since 2013 the initial refilling has been observed. Zun-Torey Lake dried up in fall 2017. Changes in water level and water chemistry determined plankton biodiversity transformation. Fluctuations of plankton communities were different for each lake and conformed the phases of the hydrological cycle. We identified four stage changes in plankton associations during the aridification of Zun-Torey Lake, and three stage changes in plankton associations as the water level fell and through the initial refilling phase for Barun-Torey Lake.

Phytoplankton species richness as an ecological indicator in a subtropical, human‐regulated, fragmented river

AbstractSince the serial discontinuity concept (SDC) of rivers is proposed, few studies have tested it in a highly fragmented river ecosystem. In this study, environmental factors, phytoplankton species richness, and SDC predictions were demonstrated along the 13 cascade dams in a subtropical river (China). Our results indicated that among environmental factors, water temperature and transparency have seasonal differences, and river width has spatial differences; total species richness (TSR) increases from upstream to downstream, and distance is the reason for its variation. In addition, TSR also has spatial variations in each cascade dam, with the maximum or minimum value of each cascade section often occurring near the dam. A predictive model was constructed and revealed that seasonal differences in species richness were more significant than spatial differences, which were mainly observed during wet periods. Taken together, these results suggest that the construction of cascading dams enhances spatial differences in phytoplankton species richness, especially during periods of abundant water. In addition, environmental parameters such as water temperature, pH, and DO and TSR all support SDC predictions. In the future, we will continue to investigate this aquatic ecosystem to study more phytoplankton‐related indices affected by the cascade damming, and hope to fully validate the SDC predictions.

Impact of the Construction of New Port Facilities on the Biomass and Species Composition of Phytoplankton in the Neva Estuary (Baltic Sea)

The construction of new port facilities and the creation of new lands is a natural consequence of the rapid growth in the population of ocean coastlines. Despite the fact that such human activity is becoming more and more widespread, its impact on various components of aquatic ecosystems, including phytoplankton, is still poorly understood. The aim of the study was to assess the effect of the large-scale construction of new port facilities on biomass and taxonomic composition of phytoplankton in the Neva Estuary (northeastern Baltic Sea). Studies have shown that digging and displacing large amounts of bottom sediments during these works led to a significant increase in suspended mineral matter and a decrease in water transparency in the estuary. This significantly reduced the species richness and biomass of phytoplankton. However, the analysis of beta diversity did not show significant changes in the phytoplankton community during the periods of port construction and the periods when no works were carried out. The changes mainly concerned rare species, while the occurrence and biomass of dominant and subdominant species changed to a lesser extent. Due to various adaptations, the phytoplankton species common in the estuary are apparently able to survive under prolonged shading and successfully compete with species that are unable to withstand the lack of light for a long time. To correctly take into account the effects of the construction of new port facilities on phytoplankton and, if possible, minimize it, additional studies of the ecology of certain phytoplankton species, their relationships, and physiological responses to various environmental factors are required.

Phytoplankton Community Response to Environmental Factors along a Salinity Gradient in a Seagoing River, Tianjin, China.

A river-estuary ecosystem usually features a distinct salinity gradient and a complex water environment, so it is enormously valuable to study the response mechanism of living organisms to multiple abiotic factors under salinity stress. Phytoplankton, as an important part of aquatic microorganisms, has always been of concern for its crucial place in the aquatic ecosystem. In this study, phytoplankton data and 18 abiotic factors collected from 15 stations in Duliujian River, a seagoing river, were investigated in different seasons. The results showed that the river studied was of a Cyanophyta-dominant type. Salinity (SAL) was the key control factor for phytoplankton species richness, while water temperature (WT) was critical not only for species richness, but also community diversity, and the abundance and biomass of dominant species. Apart from WT, the abundance and biomass of dominant species were also driven by total nitrogen (TN), nitrate (NO3-), pH, and water transparency (SD). Moreover, total dissolved phosphorus (TDP), pH, and chemical oxygen demand (COD) were crucial for community diversity and evenness. The bloom of dominant species positively associated with TDP led to lower diversity and evenness in autumn. In addition, when available nitrogen was limited, Pseudoanabaena sp. could obtain a competitive advantage through the N2 fixation function. Increased available nitrogen concentration could favor the abundance of Chlorella vulgaris to resist the negative effect of WT. The results show that Oscillatoria limosa could serve as an indicator of organic contamination, and nutrient-concentration control must be effective to inhibit Microcystis bloom. This could help managers to formulate conservation measures.

Species Richness, Diversity and Distribution of Phytoplankton in Fertilised Ponds of the Western Highlands Agro-Ecological Zone of Cameroon

In developing countries, advanced aquaculture techniques are still at the embryonic stage. This study was carried out from January to December 2021 in the ponds of the West Cameroon Region and at the Ichthyology and Applied Hydrobiology Research Unit of the University of Dschang with the aim of contributing to a better understanding of species richness and distribution of phytoplankton populations in fertilised ponds. For this purpose, a total of fifteen (15) ponds including 03 in Bamendou (fertilised with cow dung), four in Batié (two fertilised with pig manure and two with wheat bran), one in Dschang (fertilised with chicken manure), four in Fokoué (two fertilised with pig manure and two unfertilised), and three in Foumbot (fertilised with cow dung), were assessed. These ponds were chosen based on the availability of fish farmers and the type of fertiliser administered. Together with water physicochemical properties measurement, phytoplankton sampling was done between 6 a.m. and 8 a.m. on a monthly basis. The results showed that phytoplankton species and genera richness was higher in unfertilised ponds in Fokoué ponds and in animal feed enriched ponds in Batié, respectively. However, the highest family richness was obtained in Dschang receiving chicken manure with a percentage of 88.8% of the total family richness. The species Microcystis aeroginosa exhibited the highest species frequency (57%) out of all the species recorded in the ponds of Batié fertilised with pig manure. The lowest Shannon-Weaver diversity indices and Piélou evenness indices were recorded in the Fokoué ponds independent of the type of fertiliser, and in the Dschang ponds receiving chicken manure. The outputs of this work are better proposals for the production of phytophagous or bulldozer fish, such as carp, in relation to the site and the type of fertilisers in the Western highlands agroecological zone of Cameroon in particular and the world in general.

Environmental factors indirectly reduce phytoplankton community stability via functional diversity

The biodiversity-stability relationship is a fundamental subject of ecological research. Considerable evidence demonstrates that biodiversity can either increase or decrease stability. Most relevant research mainly focuses on grassland and forest ecosystems. The biodiversity-stability relationship in aquatic ecosystems and the underlying mechanisms remain poorly understood. To fill the gap, we conducted a year-long study on the phytoplankton of reservoir ecosystems in the Xiangxi Bay of Three Gorges Reservoir (TGR) to test the following hypotheses: (H1) phytoplankton species richness and functional diversity directly reduce phytoplankton community stability in reservoir ecosystems; (H2) nutrient enrichment and water temperature increasing directly reduce phytoplankton community stability; and (H3) nutrients and water temperature indirectly reduce phytoplankton community stability via biodiversity. The structural equation model (SEM) found that functional diversity (community-weighted means of traits and functional divergence) had significant negative correlations with phytoplankton community stability (p < 0.05), while the species diversity had no significant correlation with phytoplankton community stability (p > 0.05). This finding partially supported the hypothesis H1, which suggested that the functional diversity had a closer tie with stability than the species diversity. SEM did not find any direct effect of environmental factors on phytoplankton community stability, which rejected our hypothesis H2. Instead, SEM found that water temperature and phosphate decreased phytoplankton community stability by increasing the first principal component of the community-weighted means of traits (CWM_PC1), which supported hypothesis H3. Further analysis showed that the increased water temperature and phosphate concentration can promote “r-strategists” species (larger CWM_PC1), which are less resistant to environmental disturbances, therefore decreasing the phytoplankton community stability. Our study highlights the importance of functional diversity in maintaining the relationship between biodiversity and stability in the phytoplankton community, which may provide a mechanistic understanding of the biodiversity-stability relationships in aquatic ecosystems.

Multiple phytoplankton community responses to environmental change in a temperate coastal system: A trait-based approach

The effect of environmental change in structuring the phytoplankton communities of the coastal waters of the Eastern English Channel was investigated by applying a trait-based approach on two decades (1996-2019) of monitoring on diatoms andPhaeocystis. We show that phytoplankton species richness in an unbalanced nutrient supply context was influenced by wind-driven processes, ecological specialization for dissolved inorganic phosphorous, temporal niche differentiation, and a competition-defense and/or a growth-defense trade-off, a coexistence mechanism where weak competitors (i.e., slower growing) are better protected against predation. Under the influence of both environmental perturbations (e.g., wind-driven processes, freshwater influence, unbalanced nutrient levels) and biotic interactions (e.g., competition, predation, facilitation), phytoplankton species exhibited specific survival strategies such as investment on growth, adaptation and tolerance of species to environmental stresses, silicification and resource specialization. These strategies have led to more speciose communities, higher productivity, functional redundancy and stability in the last decade. Our results revealed that the unbalanced nutrient reduction facilitatedPhaeocystisblooms and that anthropogenic climate warming and nitrate reduction may threaten the diatom communities of the eastern English Channel in a near future. Our results provide strong support for biogeographical historical and niche-based processes in structuring the phytoplankton community in this temperate region. The variety of species responses that we characterized in this region may help to better understand future changes in pelagic ecosystems, and can serve as a basis to consider functional approaches for future ecosystem management.

Improvement of Water Quality by Light-Emitting Diode Illumination at the Bottom of a Field Experimental Pond

Remediation of water quality by stimulating algal photosynthesis using light-emitting diodes (LEDs) has attracted attention, but few studies have examined this in outdoor freshwater environments. To understand the effects of LED illumination on water quality, the dissolved oxygen (DO), temperature, pH, and electric conductivity were monitored over 5 months in three depressions with or without a red/blue LED light at the bottom of an experimental pond. The effects of the blue LED on water quality were evident in the period with less rainfall after the change of water quality to an equilibrium state; DO and pH were higher, and EC was lower for the blue LED than for the control. The diel changes of these variables were also lower for the blue LED. The effects of the red LED on DO and pH were also evident, but to a lesser extent compared to those of the blue LED. A vertical mixing of water associated with a nighttime cooling of the surface water was suggested by a rapid DO increase after a temperature decrease in the control. Such internal water circulation and an inflow of water after rainfall might have obscured the LED effects in the rainy period. The bottom water of the blue LED had a higher density and species richness of phytoplankton than that of the control at the end of the experiment. A lower density of phytoplankton and higher nutrient concentrations in the red LED might have been due to a higher density and feeding activity by zooplankton. Our results confirmed the applicability of LED illumination in stimulating algal photosynthesis, and in improving the oxygen condition of the bottom water in freshwater ponds.

Seasonal and spatial occurrence of plankton and environmental variables in Ogun coastal water on the Bight of Benin

The influence of environmental variables on the seasonal and spatial distribution of plankton was studied for 24 months between February 2015 and January 2017 in the marine coastal water of Ogun State, Nigeria. The coastline was stratified into three sampling stations, and surface water samples were collected monthly per station for physico-chemical and plankton analyses. Mean values of physico-chemical parameters were: temperature (28.60±0.27°C), salinity (29.25±0.45‰), pH (7.38±0.07), electrical conductivity (42.13±0.33μS/l), total dissolved solids (29.59±0.30mg/l), dissolved oxygen (6.48±0.07mg/l), phosphate (1.36×10-2±0.39mg/l) and nitrate (2.25×10-2±0.65mg/l). The dominant phytoplankton and zooplankton groups were Diatomaceae (42.06%) and Calanoids (25.42%), respectively. Spatial diversity analysis of plankton in the study area showed that the highest (19, 35) species richness and abundance (5703, 12,452) for phytoplankton and zooplankton, respectively occurred in Site 3. Seasonal species richness of phytoplankton and zooplankton was higher in the wet (27, 40) than the dry (23, 38) season. Canonical correspondence analysis explained 77.8% of the influence of environmental variables on plankton distribution. Water temperature, dissolved oxygen, salinity, phosphate, pH, TDS and nitrate were the most marked factors that affected the distribution and abundance of plankton.

Impact of cyanobacterial bloom intensity on plankton ecosystem functioning measured by eukaryotic phytoplankton and zooplankton indicators

Cyanobacterial blooms are global threats to freshwater ecosystem functioning, human health, and ecoservices. We assessed impacts of cyanobacterial bloom intensity on plankton ecosystem functioning using eukaryotic phytoplankton and zooplankton indicators and associated key physicochemical data collected from four seasons of two years at 24 evenly distributed sites in Lake Taihu that has year-around cyanobacterial blooms. Our analyses involved comparison of four site-groups with different bloom intensities and analyzing all sampling sites together using comparison, hierarchical partitioning analysis, generalized additive mixed model, and structural equation model. We found that cyanobacterial abundance positively associated with TP and temperature (negatively with TN:TP), while phytoplankton positively associated with TN. There was an inverse relation trend between relative abundances of phytoplankton and cyanobacteria, but there was no clear trend between absolute abundances of phytoplankton and cyanobacteria. Rotifers were most dominant when cyanobacteria were unabundant, while cladocerans presented higher abundance when cyanobacteria were in high abundance. Phytoplankton functional richness and species richness negatively and zooplankton functional richness and species richness positively associated with cyanobacterial bloom intensity. Cyanobacterial bloom intensity negatively associated with resource use efficiencies (RUEs) of phytoplankton and rotifers, and positively associated with RUE of cladocerans. Our analytical approach of integrating comparison of site-groups and analyzing all sites together uncovered how cyanobacterial bloom intensity shifted and altered physicochemical and biological conditions and plankton ecosystem functioning, and identified the mechanism and strength of the interactive linkages among physicochemical and biological indicators. Although our results may be different from oligotrophic lakes or reservoirs, our findings provide new insights in understanding the impacts of cyanobacterial bloom intensity on the dynamics of plankton communities and ecosystem functioning for polymictic eutrophic lakes, which may have broad application in enhancing the knowledge of this subject and provides the science base for managing polymictic eutrophic lake water quality and ecosystem functioning.

Predictable shifts in diversity and ecosystem function in phytoplankton communities along coastal salinity continua

AbstractSalinity is a major environmental predictor of phytoplankton species richness and composition. We hypothesize that the variation in phytoplankton richness along coastal salinity gradients is reflected in essential ecosystem functions like resource use efficiency (RUE)—the proportion of limiting resource that is converted into biomass. To test the hypothesis, we analyzed time series of phytoplankton and environmental variables from the Chesapeake Bay and the Baltic Sea. We analyzed the relationship among salinity, diversity, and RUE in bivariate and interaction association, and in structural equation model (SEM)—a form of path analysis to resolve multivariate relationships among interrelated variables. We concluded that the intrusion of marine water will lead to rapid change in species diversity on the fresh side. Despite diversity drop, individual community functions, like RUE, remain relatively resilient, reflecting functional redundancy. We propose that the salinity gradient also reflects trophic complexity, allowing stable resource use at reduced diversity.

Phytoplankton community characteristics and the underlying drivers under organic and conventional agricultural management

为了解不同农业施肥管理方式对水体浮游植物群落的影响，本研究以江苏句容戴庄有机示范村和常规农业管理区池塘浮游植物为对象，分析冬夏两季浮游植物群落特征及相关水环境因子.结果表明：冬季有机和常规农业区域的浮游植物分别检到7门95种和7门111种，夏季分别检到7门102种和6门112种，有机农业区浮游植物由冬季的隐藻-绿藻型向夏季的蓝藻-绿藻型变化，常规农业区从隐藻-绿藻型向蓝藻-硅藻型变化，蓝藻逐渐取代隐藻的优势地位.夏季各池塘浮游植物alpha多样性没有显著的区域差异，但冬季常规农业区浮游植物物种丰富度、蓝藻和裸藻的Shannon-Wiener多样性指数显著较高.指示物种分析显示，谷皮菱形藻（Nitzschia palea）和梅尼小环藻（Cyclotella meneghiniana）为有机农业区指示物种，而梭形裸藻（Euglena acus）、针形纤维藻（Ankistrodesmus acicularis）、肘状针杆藻（Synedra ulna）和狭形纤维藻（Ankistrodesmus angustus）为常规农业区指示物种，此6种藻为中、富营养化藻类，说明水体氮磷营养盐浓度较高，这与周围农田氮磷流失密切相关.Pearson相关性分析表明，有机农业区浮游植物alpha多样性与氮磷浓度的相关性不显著，但常规农业区浮游植物物种丰富度和Pielou均匀度与磷酸盐、总氮、氨氮和pH值显著相关.Mantel检验表明，有机农业区群落相异性仅在冬季受到总氮和氨氮的显著影响；而常规农业区在冬夏季受到氮磷两类营养盐的交替影响.本研究结果初步揭示了有机和常规农业区水体浮游植物群落结构特征及其影响因素，为区域水生生物多样性保护与稻田施肥管理的优化提供科学基础.;In order to explore the effects of different agricultural fertilization management on the phytoplankton community, the phytoplankton community characteristic and water environmental factors were investigated in winter and summer in Daizhuang organic village and conventional farming area of Jurong, Jiangsu Province. Our results showed that the phytoplankton communities were composed of 95 and 111 species of 7 phyla in organic (OFR) and conventional farming regions (CFR) in winter, 102 species of 7 phyla and 112 species of 6 phyla in summer, respectively. The phytoplankton varied from Cryptophyta-Chlorophyta type in winter to Cyanophyta-Chlorophyta type in summer in OFR, and from Cryptophyta-Chlorophyta type to Cyanophyta-Bacillariophyta type in CFR, indicating that Cyanophyta gradually replaced the dominant position of Cryptophyta. There was no significant difference in phytoplankton alpha diversity between organic and conventional farming ponds in summer, but the phytoplankton species richness and Shannon-Wiener diversity of Cyanophyta and Euglenophyta in CFR was significantly higher than that in OFR in winter. The IndVal analysis further revealed that Nitzschia palea and Cyclotella meneghiniana were the indicative species in OFR, while Euglena acus, Ankistrodesmus acicularis, Synedra ulna and Ankistrodesmus angustus were the indicative species in CFR. These algae often occurred in meso-eutrophic waters, indicating that the concentration of nitrogen and phosphorus in water was higher. This may be closely related to the nitrogen and phosphorus runoff. Pearson correlation analysis showed that there was no significant relationship between phytoplankton alpha diversity and environmental factors in two regions, but species richness and Pielou's evenness in CFR were significantly correlated with phosphate, total nitrogen, ammonia nitrogen and pH. Mantel test showed that the community dissimilarity in OFR was only significantly affected by total nitrogen and ammonia nitrogen in winter. While in CFR, community dissimilarity was affected by the alternation of nitrogen and phosphorus nutrients in winter and summer. These findings should be useful for future efforts to recover biodiversity and optimize fertilization management.

Phytoplankton and water quality of some tributaries of the Ob River

Based on the materials of studies of phytoplankton of the tributaries of the Ob (Tom’, Ket’, Vasyugan) in the summer of 2019, the species composition, taxonomic structure, abundance and biomass of phytoplankton were established, the water quality class and trophic status were determined. The basis of the species richness of phytoplankton in the tributaries is created by green algae (Chlorophyta), the parameters of alpha diversity indicate the average complexity of the structure of phytoplanktocenosis. In terms of phytoplankton biomass, the trophic status of the rivers varied from mesotrophic to eutrophic category, the water quality class corresponded to class 3 “satisfactory purity”.