Search Results (121)

Artificial reservoirs in arid regions provide unique ecological environments for studying the spatial and functional dynamics of plankton communities under the combined stressors of climate change and anthropogenic activities. This study conducted a systematic investigation of the phytoplankton community structure and its environmental drivers in 17 artificial reservoirs in the Ili region of Xinjiang in August and October 2024. The Ili region is located in the temperate continental arid zone of northwestern China. A total of 209 phytoplankton species were identified, with Bacillariophyta, Chlorophyta, and Cyanobacteria comprising over 92% of the community, indicating an oligarchic dominance pattern. The decoupling between numerical dominance (diatoms) and biomass dominance (cyanobacteria) revealed functional differentiation and ecological complementarity among major taxa. Through multivariate analyses, including Mantel tests, principal component analysis (PCA), and redundancy analysis (RDA), we found that phytoplankton community structures at different ecological levels responded distinctly to environmental gradients. Oxidation-reduction potential (ORP), dissolved oxygen (DO), and mineralization parameters (EC, TDS) were key drivers of morphological operational taxonomic unit (MOTU). In contrast, dominant species (SP) were more responsive to salinity and pH. A seasonal analysis demonstrated significant shifts in correlation structures between summer and autumn, reflecting the regulatory influence of the climate on redox conditions and nutrient solubility. Machine learning using the random forest model effectively identified core taxa (e.g., MOTU1 and SP1) with strong discriminatory power, confirming their potential as bioindicators for water quality assessments and the early warning of ecological shifts. These core taxa exhibited wide spatial distribution and stable dominance, while localized dominant species showed high sensitivity to site-specific environmental conditions. Our findings underscore the need to integrate taxonomic resolution with functional and spatial analyses to reveal ecological response mechanisms in arid-zone reservoirs. This study provides a scientific foundation for environmental monitoring, water resource management, and resilience assessments in climate-sensitive freshwater ecosystems. Full article

Land use composition, water level fluctuations (WLFs), and biogeographical factors are recognized as key drivers of phytoplankton dynamics in reservoir ecosystems. This two-year study presents the first assessment of the combined effects of catchment land use, WLFs, and geographical distance on phytoplankton biomass and community composition across twelve Mediterranean reservoirs in Cyprus, which serve primarily for drinking water supply and irrigation. The results show that higher phytoplankton biomass was recorded in reservoirs whose catchments had >30% coverage by developed land (urban and agricultural), suggesting that increased anthropogenic pressures may lead to nutrient enrichment and elevated productivity. However, despite elevated biomass, no consistent spatial patterns were observed in phytoplankton community composition. The geographical distance between reservoirs had only a minor effect on species distribution, implying that other factors—such as water residence time or hydrological variability—play a more prominent role in shaping community structure. Phytoplankton biomass maxima were most often recorded during periods of elevated water levels and were typically dominated by Chlorophyta, Dinoflagellata, Bacillariophyta, and Charophyta. The pronounced temporal variability in species composition across all reservoirs points to a highly dynamic system, where environmental fluctuations strongly influence community assembly. This study provides the first comprehensive data on phytoplankton in Cyprus reservoirs, highlighting the importance of land use and hydrological regulation for water quality management in similar settings. Importantly, this baseline dataset can support the implementation of the Water Framework Directive (WFD) by contributing to the definition of ecological status classes, establishing reference conditions, and guiding future monitoring and assessment efforts. Expanding such datasets through coordinated, basin-wide monitoring initiatives is essential to improve our understanding of phytoplankton dynamics and their role in ecosystem functioning under the pressures of climate change and intensified land use in this Mediterranean “hot spot”. Full article

Phytoplankton are essential indicators of aquatic ecosystem health. Traditional phytoplankton detection methods using microscopy struggle to identify species with small particle sizes or unclear morphological characteristics. In contrast, molecular methods have high accuracy but struggle to simultaneously detect prokaryotic and eukaryotic organisms due to primer specificity. As algal blooms can be caused by both prokaryotes and eukaryotes, methods that can detect both are required. This study used both microscopic detection and high-throughput sequencing methods to analyze phytoplankton in seagoing waters in eastern coastal China. Two high-throughput sequencing primers targeting 16S rDNA for prokaryotes and 18S rDNA for eukaryotes were used, and the results were compared with those of microscopic analysis. Microscopy identified 230 phytoplankton species across 73 genera, mainly belonging to Bacillariophyta, Chlorophyta, Euglenophyta, Cyanophyta, Dinophyta, and Chrysophyta. Twenty-four species across 16 sampling stations exceeded 1 million cells/L. High-throughput sequencing yielded 8642 prokaryotic and 7375 eukaryotic operational taxonomic units, with 432 identified as phytoplankton. Chlorophyta and Bacillariophyta had the highest species richness, accounting for 34% and 17%, respectively. High-throughput sequencing detected more species than microscopic detection but relied on gene reference databases and provided only the relative abundance of species based on operational taxonomic unit counts. Full article

Phytoplankton serve as crucial producers in marine ecosystems, and their community composition and populations’ dispersion directly or indirectly influence the productivity of marine waters via the trophic cascade effect within the food chain. A survey was undertaken in September 2021 and March, April, and November 2022 to examine the phytoplankton structure and the environmental variables influencing ecological niche differentiation in the waters of Tahe Bay in Lushun, Dalian city, China. The findings indicated that there are 83 species representing forty-one genera and six phyla, with an annual mean abundance of 22.13 × 10⁴ ind·m⁻³, predominantly represented by Bacillariophyta (65 species, constituting 78.31% of the total species). The phytoplankton richness indices varied from 0.83 to 4.99, diversity indices ranged from 2.03 to 2.80, and evenness indices spanned from 0.28 to 0.84. Pearson’s correlation between phytoplankton abundance and community diversity with environmental parameters, including water temperature, salinity, pH, DO, NH₃-N, and NO₃-N, was substantial in Tahe Bay’s waters. The dominant species, comprising 20 species across three phyla, primarily include broad-niche species, with Paralia sulcata being the most prevalent species, except during summer. The extent of ecological niche overlap among the dominant species varied by season, exhibiting 40.0% severe overlap in September 2021, 100.0% severe overlap in March 2022, 93.0% severe overlap in April 2022, and 58.0% severe overlap in November 2022. The findings of redundancy analysis (RDA) and canonical correspondence analysis (CCA) revealed that COD, water temperature, NO₃-N, DIP, NO₂-N, and NH₃-N are the primary environmental variables influencing the ecological niche differentiation of dominant species of phytoplankton. The results of the study elucidate the alteration rules of dominant species and the stability of the community structure of the phytoplankton community in this sea area, thereby offering a theoretical foundation for the scientific assessment of the ecological health of the area and the sustainable utilization of marine biological resources. Full article

To evaluate the change trends of plankton in inland saline–alkaline water bodies, this study investigated the ecological restoration and rational development of saline–alkaline lakes in northwest China. From June to October 2023, phytoplankton communities in a high-salinity lake in Alar City, Xinjiang, were analyzed using standard survey methods for inland natural waters. Biodiversity indices were calculated, and redundancy analysis (RDA), Spearman’s correlation analysis, and Mantel test were carried out to assess the functional community structure of phytoplankton and its environmental drivers. In total, 115 phytoplankton taxa belonging to seven phyla were identified. The densities ranged from 23.76 × 10⁵ to 53.54 × 10⁷ cells/L. Bacillariophyta and Cyanophyta were the dominant phyla, accounting for 41.7% and 27.8% of the total taxa, respectively. The dominant species included Microcystis spp., Merismopedia sp., Cyclotella meneghiniana, and other algae. Spearman correlation analysis revealed that salinity, water temperature (WT), Na⁺, TDS, HCO₃⁻, Cl⁻, and K⁺ were key environmental factors significantly influencing phytoplankton community structure. Mantel tests confirmed that salinity (SAL), TDS, DO, and major ions (K⁺, Na⁺, CO₃²⁻) served as key determinants of spatiotemporal phytoplankton community distribution (p < 0.05). RDA results indicated that WT, TDS, alkalinity (ALK), pH, salinity, and Na⁺ were the key factors driving seasonal variations in phytoplankton communities. Notably, decreasing salinity and ion concentrations stabilized the phytoplankton community structure, maintaining high-diversity indices. This highlights the positive impact of ecological restoration measures, such as fisheries-based alkalinity control and systematic environmental management, on the health of saline–alkaline lake ecosystems. These findings provide important insights for the sustainable development of saline–alkaline fisheries and the conservation of aquatic biodiversity in arid regions. Full article

This study reports two novel species, Gogorevia contracta sp. nov. and G. recticentralis sp. nov., which were isolated from freshwater environments in South Korea. Using an integrative taxonomic approach, we conducted morphological analyses using light microscopy and scanning electron microscopy, along with molecular phylogenetic investigations using SSU rRNA and rbcL gene sequences. Phylogenetic reconstructions highlighted the distinct characteristics of both species, confirming their classification within the genus Gogorevia and elucidating their evolutionary relationships. Morphologically, G. contracta was characterized by a bow-tie-shaped central area and circular depressions in the rapheless valve, whereas G. recticentralis exhibited a rectangular-to-wedge-shaped central area with parallel striae near the center of the raphe valve. Our findings highlighted the ecological significance of Gogorevia species and suggested their potential role as bioindicators of water quality in relatively unpolluted freshwater systems. Over the past decade, our research has focused on the taxonomic and ecological study of diatoms in the Han River system and identified 136 species, including nine newly described taxa. The findings of the present study contribute to a growing understanding of Gogorevia diversity, underscore the importance of region-specific diatom indices, and support the integration of morphological and molecular methods into diatom systematics. Full article

Liangzi Lake, a typical shallow lake in the middle reaches of the Yangtze River, is important for water resource and biodiversity conservation. With the development of urbanization, anthropogenic activities have posed serious threats to the water quality and biodiversity of Liangzi Lake. To assess the aquatic ecosystem health of Liangzi Lake, the structure, the environmental response, and the interactions of plankton were investigated in 2022 and 2023. The results indicated that water temperature was a pivotal factor regulating plankton dynamics, with the assemblage patterns predominantly shaped by the phytoplankton species, which were Bacillariophyta in spring and Chlorophyta in summer. In terms of the phytoplankton, dissolved oxygen and the N:P ratio significantly affect cyanobacteria distribution. The high biomass and abundance of cyanobacteria in summer highlight the potential risk of harmful algal blooms. In contrast to the phytoplankton, the zooplankton exhibited enhanced resilience to changes in the surrounding environment. Rotifera was the dominant group in summer in terms of both abundance and biomass. Most core genera of plankton were jointly identified by eDNA metabarcoding and microscopical analysis, and eDNA metabarcoding had advantages in revealing a higher diversity. However, some taxa among rotifers such as Liliferotrocha were only identified using microscopical analysis. Therefore, a combination of both the methods is recommended to better understand the structuring mechanisms of plankton assemblages in lake ecosystems. Full article

In this work, the toxicity level of nano- and microparticles obtained by underwater welding was assessed. The toxicity of nano- and microparticles obtained by underwater welding was evaluated on three types of marine microalgae: Heterosigma akashiwo (Ochrophyta), Porphyridium purpureum (Rhodophyta), and Attheya ussuriensis (Bacillariophyta). The aim was to study the environmental risks associated with the ingress of micro- and nanoparticles of metal oxides into the marine environment. Water samples containing suspensions from wet welding and cutting processes were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) to determine heavy metal concentrations. Biotesting included evaluation of growth inhibition, cell size change, and membrane potential of microalgae using flow cytometry. The results showed that samples APL-1 and APL-2 (flux-cored wire) were the most toxic, causing concentration-dependent growth inhibition of H. akashiwo and A. ussuriensis (p < 0.0001) as well as membrane depolarization. For P. purpureum, ELc and ELw (coated electrodes) samples stimulated growth, indicating species-specific responses. The stability of the nanoparticles and their bioavailability were found to play a key role in the mechanisms of toxicity. The study highlights the need to control the composition of materials for underwater welding and to develop environmentally friendly technologies. The data obtained are important for predicting the long-term effects of pollution of marine ecosystems by substances formed during underwater welding. Full article

The phytoplankton communities in lakes change seasonally within competitive areas, referred to as seasonal succession, which results in high compositional diversity if conditions remain stable. However, glacial lakes are generally far from human and terrestrial influences due to their location so very few species can be identified and large changes in phytoplankton composition cannot be anticipated. Nonetheless, molecular techniques, as well as classical methods, help us to determine the existence of different species. Additionally, these techniques allow us to evaluate the ecology of glacial lakes from different perspectives with developing technology. Horseshoe Island is located in the area known as Marguerite Bay on the Peninsula region in western Antarctica. This study was carried out to determine phytoplankton genome biodiversity by using the metagenomic analysis method used in 18S rRNA, 16S rRNA, and 23S rRNA gene analyses. 16S rRNA and 23S rRNA gene analyses revealed that bacteria belong to broadly distributed Cyanobacteria taxa, whereas 18S rRNA gene analysis revealed other eukaryotic phytoplankton groups. This method was used for the first time for Horseshoe Island lakes (Col 1, Col 2, Skua, and Zano), and species belonging to Cyanobacteria, Chlorophyta, Ochrophyta, and Bacillariophyta were identified. As a result, the phytoplankton genomic diversity of shallow and oligotrophic glacial lakes was determined, and benthic algal species were also identified in the water samples. These results indicate that benthic algae associated with the sediment can also contribute to aquatic phytoplankton communities in addition to oligotrophic lake phytoplankton biodiversity. Cyanobacterial biodiversity can also be recognized as a sentinel by which to monitor adaptation responses to climate change in this rapidly warming region. Full article

Thermomineral springs are unique aquatic habitats characterized by high temperatures or mineral-rich water and often host specialized microbial communities. In Serbia, these springs represent an important but under-researched ecological resource whose diverse physicochemical properties are shaped by their geological context. In this study, the physical and chemical properties of Serbian thermomineral springs and their relationship with phototrophic communities in different substrates are investigated. Phototrophic biofilms were categorized into fully submerged and splash zone biofilms, with the former showing higher primary production. Cyanobacteria, Chlorophyta, and Bacillariophyta were recorded, with Bacillariophyta being the predominant division in terms of diversity, followed by Cyanobacteria. Among Cyanobacteria, coccoid forms like Aphanocapsa, Chroococcus, Gloeocapsa and Synechococcus dominated splash zones, while trichal forms such as Leptolyngbya, Oscillatoria and Pseudanabaena were abundant in submerged biofilms, forming thick mats. Unique cyanobacterial taxa, including Desertifilum, Elainella, Geitlerinema, Nodosilinea and Wilmottia, were identified through molecular analysis, underscoring the springs’ potential as habitats for specialized phototrophs. Diatom communities, dominated by Nitzschia and Navicula, exhibited site-specific species influenced by microenvironmental parameters. Statistical analysis revealed ammonia, total nitrogen, and organic carbon as key factors shaping community composition. This study enhances the understanding of these ecosystems, emphasizing their conservation importance and potential for biotechnological applications. Full article

The dynamic changes in plateau river ecosystems and the driving mechanisms of environmental factors have garnered significant attention. Phytoplankton, a core component of aquatic ecosystems, can directly reflect changes in the aquatic environment. This study focuses on the phytoplankton in the Lhasa River Basin, including the riverbed from the source to the river mouth, five largest tributaries, and two adjacent wetlands. We analyzed the spatial and temporal variation characteristics of phytoplankton and explored the environmental driving mechanisms based on four field surveys conducted between September 2019 and March 2021. Results showed that a total of 127 species of phytoplankton from six algal phyla were identified, including Cyanobacteria. Among these, Bacillariophyta was the dominant group, accounting for 41.7% of the identified species. Spatially, phytoplankton diversity showed a decreasing trend from upstream to downstream while temporally peaking in spring and autumn. Redundancy analysis revealed that upstream phytoplankton were driven by total hardness and altitude, midstream by pH and potassium ions, and downstream by nitrate and ammonium nitrogen. Classification and regression tree analysis showed total hardness, magnesium ions, and nitrite were key factors influencing phytoplankton abundance, diversity, and evenness. This study highlights the ecological dynamics and driving mechanisms of phytoplankton communities in the Lhasa River, demonstrating their high sensitivity to environmental factors. These findings could help to establish phytoplankton as critical indicators of aquatic ecosystem health and provide scientific guidance for the conservation and management of the plateau river ecosystems. Full article

Freshwater reservoirs serve as vital water sources for numerous residential areas. However, the excessive presence of nutrients, such as nitrogen and phosphorus, stimulates rapid algal proliferation, leading to the occurrence of algal blooms. To prevent this phenomenon, it is imperative to conduct regular ecological surveys aimed at assessing water quality and monitoring the dynamic composition of aquatic biological communities within the reservoir’s ecosystem. In this study, seasonal changes in water quality parameters and the spatial and temporal distribution of planktonic algae at 14 sampling sites in the Danjiangkou reservoir were analyzed. A total of 136 taxonomic units of planktonic algae were identified, belonging to 8 phyla, 41 families, and 88 genera, with the dominant algae belonging to the phyla Chlorophyta, Bacillariophyta, and Cyanophyta. The order of abundance of the algae was summer > autumn > spring > winter and Hanku > Intake > Danku > Outflow. WT, pH, DO, COD_Mn, and Chl a were the primary drivers influencing the changes in the planktonic algal community within the reservoir. Two dominant algae, Chlamydomonas debaryana and Scenedesmus quadricauda, were isolated and cultured indoors to simulate the growth behaviors of algae in the Danjiangkou reservoir. The results show that the growth of C. debaryana was severely limited by the temperature, light, and nutrient concentration, whereas the growth of S. quadricauda was slightly affected under different temperature and light conditions and could occur at low concentrations of nitrogen and phosphorus nutrients. With excess nutrient levels, excessive proliferation of S. quadricauda could potentially cause algal blooms. This study examined the growth characteristics of the dominant algae in the Danjiangkou reservoir under laboratory conditions and delved into their interdependencies with environmental factors, aiming to furnish a theoretical and experimental foundation for investigating algal community dynamics and preventing algal blooms within the freshwater reservoir. Full article

Yap diatoms—from freshwater streams through estuaries and mangroves to the marine coral reefs—had been sampled in 1988 and 2014 and a few species from the 1988 collections described in a 2009 report. The present paper documents 168 new records, including seven new species, mostly from coral reef habitats, but including some interesting new species from mangroves, and incorporates records published in taxonomic papers. In addition, 44 Mastogloia records were published separately, bringing the taxon total to 245. In the present paper, 32 records are new for Micronesia, while many others are species described from neighboring Guam in the past 15 years. The total represents probably less than one-quarter of the species present on the reef because many specimens of Navicula, Nitzschia, Amphora, etc., have so far been identified only to genus. Floristic studies of benthic diatoms are limited partly by the shortage of taxonomic studies, and we present the taxa for which we can make reasonable arguments for identification, supporting light microscopy with scanning electron micrographs whenever possible. New taxa include Ehrenbergiopsis gen. nov. for Ehrenbergiulva hauckii; Biddulphiella cuniculopsis sp. nov.; Campylodiscus tatreauae sp. nov.; Cymatoneis belauensis from Palau and Cymatoneis yapensis from Yap; Diploneis denticulata sp. nov.; Entomoneis yudinii sp. nov.; and Nitzschia pseudohybridopsis sp. nov. Interesting new records include: Achnanthes cf. brevipes; Actinocyclus decussatus; Caloneis ophiocephala; Licmophora cf. hastata; Lyrella cf. rudiformis; and an unidentified cymatosiroid. One sediment sample included the remains of a planktonic community with Chaetoceros peruvianus, Skeletonema grevillei, Thalassiothrix gibberula and two species of Lioloma, rarely seen in the oligotrophic waters of Micronesia. Full article

To explore how environmental factors affect the structure of plankton in urban rivers, we analyzed the Caowangjing River, an urban river that passes through Wuxi, to survey the water environmental factors and plankton population in different seasons. We identified 103 phytoplankton species belonging to eight phyla, with Chlorophyta, Bacillariophyta, and Cyanobacteria being the dominant groups. A total of 45 zooplankton species belonged to three classes, with Rotifera being the dominant class. Phytoplankton density was highest in the autumn, followed by the spring, and the lowest in the summer. Phytoplankton biomass, along with zooplankton density and biomass, exhibited seasonal declines. The average values of the Shannon–Wiener index, Pielou’s evenness index, and Margalef richness index were 3.58 ± 0.50, 0.72 ± 0.76, and 2.03 ± 0.31, respectively, indicating the Caowangjing River was mildly polluted based on a water quality evaluation. Redundancy analysis showed that turbidity, water temperature, and ammonia nitrogen are the key factors of phytoplankton community distribution, while water temperature, the permanganate index, and ammonia nitrogen are the key factors of zooplankton community distribution. Full article

Salt marshes support high biodiversity and provide essential ecosystem services, yet are increasingly threatened by climate change, reduced freshwater input, and human activities. This pilot study examined the physico-chemical characteristics and biodiversity of the Palud salt marsh in Istria, Croatia, during July 2021, focusing on phytoplankton, zooplankton, and macrozoobenthos communities across different habitats. The results show that while parameters like water temperature and pH remained stable, dissolved oxygen and nutrient levels fluctuated significantly. Water depth decreased due to drought and tidal oscillations, affecting salinity and nutrient concentrations. Phytoplankton communities were dominated by Bacillariophyta, with Cryptophyta, particularly Cryptomonas sp., having the highest abundance. Zooplankton communities were dominated by Rotifera, especially Brachionus plicatilis, while the macrozoobenthos communities were dominated by Ostracoda, with some variation in gastropod and chironomid abundance across sites. These findings indicate the dynamic nature of plankton and benthos communities in response to changing water levels in the Palud marsh. This study highlights the need for targeted conservation strategies to preserve the ecological integrity of Mediterranean salt marshes. Sustainable management practices must account for water level fluctuations, the role of aquatic vegetation, and the resilience of these ecosystems, emphasizing their importance in supporting biodiversity and ecosystem services in the face of environmental change. Full article