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Background: Algae play important roles in urban river ecosystems and are the cornerstones of most water quality monitoring programs. Thus, a better understanding of algal community dynamics is needed to support sustainable management of water resources in urban rivers. Results: In this study, we quantified the seasonal variations in planktonic and periphytic algal community structure in the highly urban Fenhe River and identified environmental factors affecting algal community structure and diversity. We monitored planktonic (drifting) and periphytic (attached) algal communities in the Taiyuan section of the Fenhe River over one year. The results indicated that Cyanophyta was the dominant phylum in both communities, followed by Bacillariophyta and Chlorophyta. Significant differences were observed in the composition of the planktonic and periphytic algal communities. In particular, the periphytic algal community was more diverse than the planktonic community. Water temperature and pH were the main environmental factors affecting planktonic and periphytic algal community structure, respectively, while nutrients were the most significant factor affecting planktonic and periphytic algal diversity. Ecological modeling indicated that the variations in the algal communities of the Fenhe River are mainly driven by stochastic processes. A co-occurrence network developed for the communities displayed positive interactions between the planktonic and periphytic algae. Conclusions: These findings deepen our understanding of the seasonal interaction between planktonic and periphytic algae and the driving factors affecting community structure in the Fenhe River. They also provide a theoretical basis for the managing and protecting water resources in urban river ecosystems. [ABSTRACT FROM AUTHOR]

Water scarcity and pollution pose a threat to the sustainable development of cities and society. Therefore, it is crucial to analyze the hydrochemical characteristics and carbon dynamics of water-deficient areas. Taking the Taiyuan section of Fenhe River as the research object, we systematically explored the hydrochemical characteristics of surface water and its evolutionary processes, as well as the ecological effect of algal carbonic anhydrase in carbon cycle using the hydrochemical evolution method and correlation analysis. The ternary diagram demonstrates that the main water chemical type in Fenhe River was SO42−·Cl−-Na+. The Gibbs and end-member diagrams of each ion display that the chemical composition of surface water was mainly controlled by silicate decomposition. The chemical ions originated mainly from dissolution of some minerals, such as plagioclase, halite, dolomite, calcite, and gypsum. The diatoms had a lower CO2 requirement because they exhibited a higher abundance at a lower partial pressure of CO2 (pCO2). However, high CO2 concentration had a positive effect on cyanobacteria, which reduced the active transport of HCO3−, saved the energy needed for this part of active transport, and indirectly improved the overall photosynthetic efficiency of algae. Carbonic anhydrase (CA) activity was significantly negatively correlated with pCO2 and positively correlated with HCO3− concentration, indicating that CA in water promoted the conversion of CO2 to HCO3−. The HCO3− generated from this process continued to participate in the erosion of silicate rocks, sequestering CO2 in the form of CaCO3, which has a non-negligible impact on the carbon sink in the Fenhe River. These consequences may have important implications for the biogeochemical cycling occurring in urban water. [ABSTRACT FROM AUTHOR]

The newly described chrysophyte, Mallomonas vietnamica, is reported for the first time in China from specimens collected in Guizhou Province, SW China. The morphological characteristics were studied using light and scanning electron microscopy. The species was described based on morphological characteristics, including cell size, scale size, dome, V-rib, and bristles. Subsequently, molecular sequencing of M. vietnamica was conducted and a phylogenetic tree was constructed based on concatenated SSU, LSU, and rbcL sequences. The phylogenetic tree led us to suggest raising a new section named Uncatusipedae for this species. This study provides new molecular data from the genus Mallomonas and enriches our understanding of the species diversity and geographical distribution of the genus Mallomonas in China. [ABSTRACT FROM AUTHOR]

We describe a new species of Discostella from Guiyang based on light and scanning electron microscopic observations, as well as molecular analysis. This species is morphologically distinguished from other species by a relatively smooth and slightly recessed central area with marginal striae of unequal lengths forked near the margin. Marginal fultoportulae and a single rimoportula are situated between every two costae or on the costae. Both morphological characters and the concatenated data of rbcL and SSU rDNA indicate that Discostella guiyangensis is a unique and new species. According to divergence time estimation analysis, Discostella guiyangensis is the oldest species among the Discostella species sequenced currently. In addition, we complement molecular data of Discostella asterocostata and Discostella stelligera. [ABSTRACT FROM AUTHOR]

The community structure and co-occurrence pattern of eukaryotic algae in Yuncheng Salt Lake were analyzed based on marker gene analysis of the 18S rRNA V4 region to understand the species composition and their synergistic adaptations to the environmental factors in different salinity waters. The results showed indicated that the overall algal composition of Yuncheng Salt Lake showed a Chlorophyta-Pyrrophyta-Bacillariophyta type structure. Chlorophyta showed an absolute advantage in all salinity waters. In addition, Cryptophyta dominated in the least saline waters; Pyrrophyta and Bacillariophyta were the dominant phyla in the waters with salinity ranging from 13.2 to 18%. Picochlorum, Nannochloris, Ulva, and Tetraselmis of Chlorophyta, Biecheleria and Oxyrrhis of Pyrrophyta, Halamphora, Psammothidium, and Navicula of Bacillariophyta, Guillardia and Rhodomonas of Cryptophyta were not observed in previous surveys of the Yuncheng Salt Lake, suggesting that the algae are undergoing a constant turnover as the water environment of the Salt Lake continues to change. The network diagram demonstrated that the algae were strongly influenced by salinity, NO3−, and pH, changes in these environmental factors would lead to changes in the algal community structure, thus affecting the stability of the network structure. [ABSTRACT FROM AUTHOR]

The marine and freshwater Hildenbrandia samples were collected from diverse locations of China and Japan, and morphological characterization and molecular phylogenetic analysis were conducted on these samples. Morphological measurements of freshwater specimens were consistent with the results of H. jigongshanensis, whereas cell dimensions of marine specimens were slightly larger than those of widely distributed H. rubra and H. crouanii. Phylogenetic trees based on rbcL, psbA and UPA sequences were consistent. Freshwater specimens collected in this study formed an independent clade with H. jigongshanensis supported by high values. Species attribution was confirmed further by the similar ITS2 secondary structures among the samples of H. jigongshanensis. It was found that the intraspecific divergence of rbcL gene in H. jigongshanensis was smaller than other two freshwater species H. rivularis and H. angolensis. Phylogenetic trees showed that marine specimens in this study grouped together with H. rubra samples of North America, and were different with the H. rubra samples of Europe. Combining the comparison results of CBC numbers in ITS2 secondary structure, we propose the marine samples collected in this study to be a new species Hildenbrandia qingdaoensis sp. nov. The separation of the marine and freshwater specimens was supported by the rbcL, UPA and psbA phylogeny as well as ITS2 secondary structure inference. Biogeographical reconstruction showed the ancestor of freshwater Hildenbrandia might derive from South America and dispersed from North America to Europe and then to Asian countries, which needs to be verified further with more samples and molecular evidences from South America. [ABSTRACT FROM AUTHOR]

Makinoella Okada is a genus of coccoid green algae belonging to the family Oocystaceae with typical morphological characteristics. Reports to date included only one type species. Since the genus is rarely reported, there is a lack of taxonomic research. In this study, 17 strains of this genus were collected from several different places in China, and their taxonomic studies were conducted based on morphological and molecular phylogenetic analysis. The phylogenetic results based on the analysis of ITS, chloroplast genes rbcL and tufA showed that the genus was divided into two branches. One of the branches comprised newly collected algae. Compensatory base changes (CBCs) and hemi-compensatory base changes (hemi-CBCs) within the secondary structure of the ITS-2 confirmed the branches as two species. Compared with the type species of Makinoella tosaensis, the cell size of this new branch was only about 50%, and included 2–4 colonial cells. Therefore, based on the smaller cell size, simpler colony composition, independent phylogenetic position and CBCs and hemi-CBCs, we suggest that the new clade should be designated as a new taxon of Makinoella, namely Makinoella parva. Among the four molecular markers using in this study, the rbcL and newly introduced ITS are recommended for species separation, which can help further studies to revise the species and generic concepts of the family. [ABSTRACT FROM AUTHOR]

Hildenbrandia is an early diverged lineage in Florideophyceae, Rhodophyta. The species diversity of this genus is still unresolved due to the simple morphology and limited molecular information. The mitochondrial genome of freshwater H. jigongshanensis was determined in this study. The freshwater H. jigongshanensis had a larger mitochondrial genome than the marine H. rubra and GC content was higher. Collinear alignment structure was observed between the mitochondrial genomes of H. jigongshanensis and H. rubra, except for one block that was encoded on the complement strand. More introns were found in mitochondrial genome of H. jigongshanensis than in H. rubra, and H. jigongshanensis shares the common feature with Bangiophyceae that two introns were distributed in cox1. Comparison of mitochondrial genome organization suggests that H. jigongshanensis preserves characters that could be hypothetically more similar to the ancestor of Bangiophyceae and Florideophyceae, which differ with previous studies based on chloroplast, and nuclear markers. More mitochondrial genomes and phylogenetic analyses combing nuclear, chloroplast and mitochondrial genomes are needed to clarify this discrepancy. Mitochondrion-based phylogeny in this study resulted in better solution at both the deep and recent derived nodes than single-gene phylogenies. Most protein-coding genes between H. jigongshanensis and H. rubra were identical except atp8, which was present in H. jigongshanensis while absent from H. rubra. This finding follows the trend that high Ka/Ks ratio genes are more frequently lost than low Ka/Ks ratio ones in red algae. [ABSTRACT FROM AUTHOR]

Dunaliella salina is a classic halophilic alga. However, its molecular mechanisms in response to high salinity at the post transcriptional level remain unknown. A unique halophilic alga strain, DS-CN1, was screened from four D. salina strains via cell biological, physiological, and biochemical methods. High-throughput sequencing of small RNAs (sRNAs) of DS-CN1 in culture medium containing 3.42-mol/L NaCl (SS group) or 0.05-mol/L NaCl (CO group) was performed on the BGISEQ-500 platform. The annotation and sequences of D. salina sRNAs were profiled. Altogether, 44 novel salt stress-responsive microRNAs (miRNAs) with a relatively high C content, with the majority of them being 24 nt in length, were identified and characterized in DS-CN1. Twenty-one differentially expressed miRNAs (DEMs) in SS and CO were screened via bioinformatic analysis. A total of 319 putative salt stress-related genes targeted (104 overlapping genes) by novel miRNAs in this alga were screened based on our previous transcriptome sequencing research. Furthermore, these target genes were classified and enriched by GO and KEGG pathway analysis. Moreover, 5 novel DEMs (dsa-mir3, dsa-mir16, dsa-mir17, and dsa-mir26 were significantly upregulated, and dsa-mir40 was significantly downregulated) and their corresponding 10 target genes involved in the 6 significantly enriched metabolic pathways were verified by quantitative real-time PCR. Next, their regulatory relationships were comprehensively analyzed. Lastly, a unique salt stress response metabolic network was constructed based on the novel DEM-target gene pairs. Taken together, our results suggest that 44 novel salt stress-responsive microRNAs were identified, and 4 of them might play important roles in D. salina upon salinity stress and contribute to clarify its distinctive halophilic feature. Our study will shed light on the regulatory mechanisms of salt stress responses. [ABSTRACT FROM AUTHOR]

Batrachospermaceae is an important group of freshwater red algae. Available data of the latitude, longitude, and environmental factors on Batrachospermaceae distribution in Asia were analyzed to understand the geographical distribution of Batrachospermaceae genera in Asia. Statistical analyses, including one-way ANOVA, correlation analysis, stepwise regression analysis, principal component analysis, and linear discriminant analysis were conducted to characterize variation in geographical distribution and growth environment. Results reveal high variation in geographical distribution and growth environment among different Batrachospermaceae genera in Asia. Specifically, correlations between latitude and all environmental factors exclusive of altitude are significant, and longitude is significantly correlated with all environmental factors except for average relative humidity. The geographical distribution and growth environment of different Batrachospermaceae genera significantly differed. Altitude, maximum temperature, average temperature, minimum temperature, average relative humidity, average wind speed, maximum wind speed, and atmospheric pressure all contributed to explaining differences in the geographical distribution of Batrachospermaceae genera. Combining the results of correlation analysis, stepwise regression analysis, and principal component analysis, all environmental factors contributed to the different geographical distribution of Batrachospermum, Paludicola, Sheathia, Sirodotia, and Remainder (the rest), all environmental factors but atmospheric pressure contributed to the different geographical distribution of Kumanoa, and all environmental factors but average wind speed and maximum wind speed contributed to the different geographical distribution of Virescentia. However, the correlation between these significantly related environmental factors and taxa is not necessarily causative, and many other environmental factors, such as temperature, pH, conductivity, shading, current velocity, dissolved oxygen, hardness, substrata types, and nutrients etc., are likely to have an important impact on the geographical distribution of taxa, which is an important topic for future research. [ABSTRACT FROM AUTHOR]

We detailed the valve morphology of five new species of diatom genus Nupela from wetwall communities in Yunnan Province, China, with light and scanning electron microscope. The five new species demonstrate great variability within the genus, as three of them are biraphid and two are monoraphid. In addition, variation was noted in the structure of internal proximal raphe ends, with some species having anchor-shaped ends and other species have hooked ends. The genus Nupela has grown considerably in 30 years since it was first proposed, going from a monotypic genus to over 85 taxa. Diagnosis of the genus is based on the presence of an external covering over the areolae. We discussed the systematic placement of Nupela within the naviculoid diatoms. Yunnan Province appears to harbor many endemic diatom taxa, and many regions of the province have yet to be studied. [ABSTRACT FROM AUTHOR]

Microorganisms play a key role in aquatic ecosystems. Recent studies show that keystone taxa in microbial community could change the community structure and function. However, most previous studies focus on abundant taxa but neglected low abundant ones. To clarify the seasonal variation of bacterial and microalgal communities and understand their synergistic adaptation to different environmental factors, we studied the bacterial and eukaryotic phytoplankton communities in Fenhe River that runs through Taiyuan City, central China, and their seasonal co-occurrence patterns using 16S and 18S rDNA sequencing. Results indicate that positive interaction of eukaryotic phytoplankton network was more active than negative one except winter, indicating that the cooperation (symbiotic phenomenon in which phytoplankton are interdependent and mutually beneficial) among them could improve the adaption of microbial community to the local environmental changes and maintain the stability of microbial network. The main genera that identified as keystone taxa in bacterial network were Salinivibrio and Sphingopyxis of Proteobacteria and they could respond to the variation of nitrite and make use of it, while those that identified as keystone taxa in eukaryotic phytoplankton network were Pseudoschroederia and Nannochloris, and they were more susceptible to nitrate and phosphate. Mychonastes and Cryptomonas were closely related to water temperature. However, the loss of the co-occurrence by environmental factor changes affected the stability of network structure. This study provided a reference for analyzing relationship between bacteria and eukaryotic phytoplankton and revealing potential importance of keystone taxa in similar ecological domains in carbon, nitrogen, and phosphorus dynamics. [ABSTRACT FROM AUTHOR]

The most prominent biological characteristic of Porphyridium purpureum is their unique extracellular sulfated polysaccharides that plays an important protective role against salt stress. Adaptation to stress is associated with metabolic adjustments. However, the molecular mechanisms underlying such metabolic changes remain elusive. This study presents the first transcriptome profiling of P. purpureum. A total of 8 019 assembled transcripts were identified, annotated, and classified into different biological categories and pathways based on a BLAST analysis against various databases. The in-depth analysis revealed that many of the differentially expressed genes in P. purpureum under salinities of 68 and 0 involved polysaccharide metabolism. A comparison of the gene expression levels under different salinities revealed that the polysaccharide synthetic pathway was significantly upregulated under the 68 salinity condition. The increased expression of the FBP, pfkA, CS, pgm, USP, UGP2, galE, and MPI transcripts in the polysaccharide synthetic pathway and the increase in ATP2 and ATP6 transcripts in the energy metabolic pathway revealed the molecular mechanism of high-salt adaptation. This sequencing dataset and analysis could serve as a valuable resource to study the mechanisms involved in abiotic stress tolerance in Rhodophyta. [ABSTRACT FROM AUTHOR]

Species of the red algal order Acrochaetiales mostly inhabit marine environments, with only two freshwater taxa Audouinella and Ottia. A new genus and species are described for freshwater red alga Pauciramus yunnanensis from Ailao Mountain, Yunnan, China. It is closely related to Ottia and a new order Ottiales was proposed for these genera. Pauciramus has unique combination of morphological characteristics including the following: plants caespitose and densely pulvinate, slender uniseriate filaments with well-developed rhizoids, rarely branched, cylindrical vegetative cell with a single, ribbon-shaped and parietal chloroplast, reproduction by tetrasporangia, and dense sporangial branchlet only at the upper portion of filaments. Phylogenetic analysis of sequence data from the plastid ribulose-1,5-bisphosphate carboxylase-oxygenase large-subunit (rbcL), small subunit gene of the ribosomal cistron (SSU) and barcode region near the 5′ end of the mitochondrial cytochrome oxidase subunit I (COI-5P) indicated that: the new taxon, P. yunnanensis, was in a well-supported clade with Ottia meiospora, and this clade was sister to order Palmariales and Acrochaetiales. To adhere to the principle of monophyly, a new freshwater order Ottiales including Ottia and Pauciramus is proposed. Despite the high sequence interspecific divergences and obvious morphological differences between genera Ottia and Pauciramus, seems impractical to establish a new family for a monospecific genus. Therefore, we temporarily classified Pauciramus into the family Ottiaceae, and made necessary revisions to the description to accommodate this genus. [ABSTRACT FROM AUTHOR]

Phytoplankton are not only the main bearer of the nitrogen cycle, but also a key link driving nitrogen cycle. However, most phytoplankton cannot directly use N2, and they must uptake nitrogenous nutrients (ammonium, nitrate, and urea) to meet their photosynthesis needs. We examined the uptake characteristics of several nitrogenous substrates using stable isotope technique and identified the potential nitrogen transformations in the Fenhe River. Results revealed that spring phytoplankton community composed of mainly Fragilaria, Ulothrix, Microcystis, and Synedra. Urea can meet the spring partial nitrogen requirement of phytoplankton. The large uptake rate of urea depended on urease, chlorophyll a, and nitrate concentrations as shown in random forest models. Cyanobacteria explained more than 42.8% of the total abundance at all sites in summer. Upstream was dominated by Actinastrum, and Chlorella was relevant in the downstream section. The uptake rates of ammonium were higher than those of nitrate and urea. In addition, the random forest model demonstrated that ammonium, urease, and dissolved oxygen (DO) were the major contributors to the ammonium uptake rates. Ammonium was taken up preferentially in autumn and phytoplankton (Cyclotella, Chlorella, and Pseudanabaena) appeared to be able to respond to changes in nitrogen forms by adjusting their community composition. Structural equation models demonstrated that temperature-induced changes in DO directly affected the transformations of different forms of nitrogen. At the same time, dissolved organic carbon can directly act on nutrients and then indirectly affect enzyme activity. There were great differences in the positive and negative effects of different paths in the process of nitrate reduction to nitrite and then reduction to ammonium in time and space. These findings provide a better understanding of the underlying mechanism of nitrogen uptake and the influences of interaction between environmental variables on nitrogen transformations in urban river ecosystems. [ABSTRACT FROM AUTHOR]

Background: Salinity is an essential abiotic stress in plants. Dunaliella is a genus of high-salt-tolerant microalgae. The present study aimed to compare the characterizations of D. bioculata and D. quartolecta at different levels and investigate novel genes response to salt stress. Methods and results: High chlorophyll contents were detected in D. bioculata on the 35th d of salt stress, while high lipid and carotenoid contents were detected in D. quartolecta via morphological and biochemical analyses. Physiological analysis showed that D. quartolecta cells had a smaller increase in osmotic potential, a smaller decrease in the Na+/K+ ratio and photochemical efficiency (Fv/Fm), and a lower relative conductivity than D. bioculata cells. The genomic lengths of D. quartolecta and D. bioculata were 396,013,629 bp (scaffold N50 = 1954 bp) and 427,667,563 bp (scaffold N50 = 3093 bp) via high-throughput sequencing and de novo assembly, respectively. Altogether, 25,751 and 26,620 genes were predicted in their genomes by annotation analysis with various biodatabases. The D. bioculata genome showed more segmental duplication events via collinearity analysis. More single nucleotide polymorphisms and insertion-deletion variants were detected in the D. bioculata genome. Both algae, which showed a close phylogenetic relationship, may undergo positive selection via bioinformatics analysis. A total of 382 and 85 novel genes were screened in D. bioculata and D. quartolecta, with 138 and 51 enriched KEGG pathways, respectively. Unlike the novel genes adh1, hprA and serA, the relative expression of livF and phbB in D. bioculata was markedly downregulated as salinity increased, as determined by qPCR analysis. The relative expression of leuB, asd, pstC and proA in D. quartolecta was markedly upregulated with the same salinity increase. Conclusion: Dunaliella quartolecta is more halophilic than D. bioculata, with more effective responses to high salt stress based on the multiphase comparative data. [ABSTRACT FROM AUTHOR]

The genus Sheathia consists of over 20 species primarily distributed in Asia, Europe, Oceania, North America, and Africa. However, the origin and evolution of this genus remain unclear. Two gametophyte stage specimens (SAS18052 and SAS18523) and two "Chantransia" stage specimens (YTS19161 and YTS19017) were collected from Shanxi and Henan Provinces in China, respectively. Based on morphological data, isolates YTS19161 and YTS19017 were similar to Audouinella pygmaea, whereas the morphological characteristics of SAS18052 and SAS18523 were in good agreement with the circumscription description of S. longipedicellata. Molecular sequences of rbcL, COI-5P, and psbA were used to investigate the phylogenetic, evolutionary, and biogeographic origin of the genus Sheathia. The three molecular markers supported that the two gametophyte stage specimens belong to S. longipedicellata, while the isolates YTS19161 and YTS19017 were the "Chantransia" of S. longipedicellata. Ancestral area reconstruction and divergence time estimation speculated that Sheathia originated in North America, a portion of the Pangaea at approximately 328.07–184.73 million years ago (Ma). Our relaxed molecular clock analysis suggests that the Florideophyceae diverged approximately 741.04 (894.36–631.70) Ma. The major divergences in this class involved the emergence of Nemaliophycidae [ca. 662.01 (779.83–580.51) Ma], and the split of orders Batrachospermales and Thoreales [ca. 456.10 (552.80–367.88) Ma]. [ABSTRACT FROM AUTHOR]

Environment-friendly sound measures with high algal growth inhibition efficiency are required to control and eliminate CyanoHABs. This study examined the effects of protopine on growth, gene expression, and antioxidant system of the M. aeruginosa TY001 and explored possible damage mechanism. The results revealed that higher concentrations of protopine seriously inhibited the growth of M. aeruginosa. Quantitative real-time PCR analysis showed downregulated expression of stress response genes (prx and fabZ), and DNA repair gene (recA) on days 3 and 5. The activities of antioxidant enzymes were also decreased markedly, including superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Additionally, protopine stress can significantly increase the malondialdehyde (MDA) level in cells. In conclusion, oxidative damage and DNA damage are the main mechanisms of protopine inhibition on M. aeruginosa TY001. Our studies provide evidence that alkaloid compounds such as protopine may have a potential use value as components of aquatic management strategies. [ABSTRACT FROM AUTHOR]

The allelochemical 5,4′-dihydroxyflavone (DHF) exerts a strong inhibitory effect against Microcystis aeruginosa TY001. In this study, the effects of DHF on growth, full photosynthetic performance, gene expression, and the antioxidant system of M. aeruginosa were examined to explore the possible damage mechanism. Quantitative real-time polymerase chain reaction analysis revealed downregulated expression of prx and fabZ, two photosynthesis-related genes (psaB and psbA), and a DNA repair gene (recA) on days 3 and 5. The levels of antioxidant enzymes also decreased, including superoxide dismutase, catalase, and peroxidase. Additionally, DHF significantly increased malondialdehyde and reactive oxygen species levels in cells. In conclusion, inhibited photosynthesis and oxidative damage were the main mechanisms by which DHF inhibited M. aeruginosa TY001. This study provides evidence that polyphenolic compounds, such as DHF, may be effective components of aquatic management strategies. [ABSTRACT FROM AUTHOR]

The seasonal and spatial eukaryotic phytoplankton composition in the Fenhe River was investigated based on the 18S rDNA V4 region. The relationship between phytoplankton functional groups and environmental factors was explored to effectively capture the responses of these taxa to environmental gradients and their effects on ecosystem function. Our results indicated that the Chlorophyta and Bacillariophyta had higher relative abundance than other taxa, and their diversity and richness indices in spring were higher than those in other seasons. The linear discriminant analysis effect size (LEfSe) analyses detected that the potential seasonal biomarkers included Desmodesmus, Cyclotella, Pseudoschroederia, Discostella, Scenedesmus, Monoraphidium, and Nannochloropsis; the spatial biomarkers included Amphora, Neochloris, Hindakia, Pseudomuriella, Coccomyxa, Chloroidium, Scherffelia, Chromochloris, and Scotinosphaera. The systemic evolution and distribution characteristics of the first 50 representative sequences showed that the dominant genus included Desmodesmus in spring, Pseudopediastrum in summer, Mychonastes in autumn, and Monoraphidium in winter. Main seasonal variation of phytoplankton functional groups was as follows: spring (J + F + C + X1) → summer (J + F + X1 + X2) → autumn (J + F + X1 + C) → winter (X1 + J + B + X2). Pearson correlation, redundancy analysis, and variance partitioning analysis showed temperature and phosphate were the determining factors causing the changes of phytoplankton functional groups and community composition in the Fenhe River. [ABSTRACT FROM AUTHOR]

Salt stress is an abiotic stress to plants in especially saline lakes. Dunaliella, a halophilic microalga distributed throughout salt lakes and seas, can respond to different salinity stresses by regulating the expression of some genes. However, these genes and their function and biological processes involved remain unclear. Profiling these salt-stress-related genes in a high-salt-tolerant Dunaliella species will help clarify the salt tolerance machinery of Dunaliella. Three D. salina_YC salt-stress groups were tested under low (0.51 mol/L), moderate (1.03 mol/L), and high (3.42 mol/L) NaCl concentrations and one control group under very low (0.05 mol/L) NaCl concentration and 3 transcriptome results that were deep sequenced and de novo assembled were obtained per group. Twelve high-quality RNA-seq libraries with 46 585 upregulated and 47 805 downregulated unigenes were found. Relative to the control, 188 common differentially expressed genes (DEGs) were screened and divided into four clusters in expression pattern. Fifteen of them annotated in the significant enriched Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were validated via qPCR. Their qPCR-based relative expression patterns were similar to their RNA-seq-based patterns. Two significant DEGs, the geranylgeranyl diphosphate synthase coding gene (1 876 bp cDNA) and diacylglycerol O-acyltransferase coding gene (2 968 bp cDNA), were cloned and analyzed in silico. The total lipid content, superoxide dismutase specific activity, and beta, carotene content of D. salina_YC increased gradually with increasing salinity. In addition, the expression of 11 validated genes involved in fatty acid biosynthesis/degradation, active oxygen or carotenoid metabolisms showed significant changes. In addition, algal photochemical efficiency was diminished with increasing salinity, as well as the expression of 4 photosynthesis-related genes. These results could help clarify the molecular mechanisms underlying D. salina responses to the Yuncheng Salt Lake environment and lay a foundation for further utilization of this algal resource. [ABSTRACT FROM AUTHOR]

The genus Neglectella Vodenicarov & Benderliev has a morphology similar to the well-known genus Oocystis, except for the numerous chloroplasts stacked in the surface layer of the cell. Neglectella subsequently experienced complex taxonomy changes with members being transferred in and out, and five species are now accepted. In this study, a new alga with morphology corresponding to this genus was collected in China and successfully cultured in laboratory. Morphological observations in light microscopy and transmission electronic microscopy (TEM) and phylogenetic analyses revealed that it is a new species, described here as Neglectella glomerata sp. nov. It differed from other Neglectella species due to a morphological difference in its unique mucilaginous colony with a large number of cells, multiple pyrenoids in each chloroplast, smaller cell size, and more elongated cell shape. Phylogenetic analyses placed this alga in the subfamily Eremosphaeroideae of the family Oocystaceae and showed its close relationship with Neglectella peisonis. Further morphological comparisons combined with phylogenetic results revealed three different morphological types in Neglectella. The new type represented by our new species may represent a transitional morphology in intermediate taxonomic position between the other two types. The diversity of morphological types in Neglectella suggests that further unknown species of this genus are likely to be discovered in the future. More collections and DNA sequence data will be needed in the future for this genus. [ABSTRACT FROM AUTHOR]

Virescentia guangxiensis, a new species of Virescentia from Guangxi, South China, is described and illustrated based on morphological observations and phylogenetic analysis. This species was distinguished morphologically from other species by the presence of special expansion cells with a variable shape, obovoid, spherical, pear-shaped, located in the penultimate cells of primary or secondary fascicles, rarely terminal on primary fascicles, as well as by small whorls (250–350-µm wide) and short primary fascicles (5–7 cell stories). Phylogenetic analysis of molecular data from the rbcL and COI-5P loci supported the separation of the proposed new species from other species in the genus Virescentia. This is the first species of the order Batrachospermales reported in Guangxi and the second species of the genus Virescentia reported in China. This study expands the known species diversity and geographical distribution of freshwater Rhodophyta in China. [ABSTRACT FROM AUTHOR]

Twelve putative "Chantransia" isolates were collected from six locations across Hubei, Shanxi, Guizhou, and Henan Provinces in China. Their morphological characters were evaluated via the Ward's method of hierarchical cluster analysis in SPSS software to classify phylogenetic relationships among the isolates. The morphological data revealed that isolate HN31 (called group "MALL") was distinct from the other specimens being macroscopic with large vegetative cells and monosporangia (>20 µm in diameter). The 11 other isolates were grouped into three clusters, corresponding to the species Audouinella tenella, A. hermannii, and A. pygmaea. The morphological "Chantransia" stage of the species, reportedly belonging to the orders Batrachospermales, Thoreales, and the phylogenetically distant genus Audouinella, are very similar, resulting in the difficulty to distinguish them based just on morphology. Therefore, molecular analysis of rbcL, UPA, and COI-5P was conducted to infer the phylogenetic position of all isolates in this study. All "A. tenella" and "A. hermannii" sequences belong to order Batrachospermales, while the isolate HN31 was the "Chantransia" of Thorea hispida. The six other specimens varied morphologically, but they were within the circumscription of "A. pygmaea". All three molecular markers show that all "pygmaea" isolates also represent the "Chantransia" of T. hispida. Furthermore, results from this investigation proposed a new species—Sheathia qinyuanensis, corresponding to the isolates QY1 and QY2. [ABSTRACT FROM AUTHOR]

We report on eight species of the freshwater diatom genus Gomphonema from aquatic habitats from the Yuntai Mountains of Henan Province, China. This work represents the first detailed descriptions of the freshwater diatoms from this centrally-located province in China. Of the eight taxa considered, five are new to science and another is given a "cf." designation. Four of the eight species are similar in morphological features to other, "classical" species, with external areolar occlusions forming C-shaped openings. Another species is astigmate, and has distinct siliceous papillae located marginally on the exterior of the valves; this morphology has not been recognized previously for the genus. Two of the species have internal areolar and stigma occlusions. The diversity of morphological types of species in Gomphonema may relate to the ecosystems, with more diverse ecosystems harboring greater diversity of these morphological groups of Gomphonema. [ABSTRACT FROM AUTHOR]

Large-scale, inter-basin water diversion projects have been developed to relieve water scarcity crisis and water pollution problems. Environmental status and ecosystem impacts are largely unknown for the Wanjiazhai Yellow River Diversion Project (YRDP-WJZ), a water body critical in northern China. In the current study, twelve hydrochemical indices (including Mn, Cu, Zn, Hg, Pb, NH3-N, COD-Mn, DO, BOD5, COD, TP, and TN) were collected from 2008 to 2017 based on multiple analytical approaches to understand environmental status and ecological risks. Human health risk and threats to aquatic organisms from heavy metals were assessed. Heavy metals have no regular spatial distribution. Biochemical parameters and nutrients pollute seriously in midstream and downstream, respectively. Hydrochemical indices suggested high levels of pollution in the midstream section. Water quality improved downstream of the Fenhe Reservoir, but total nitrogen and total phosphorus in the downstream section increased in recent years. The Canadian Council of Ministers of the Environment Water Quality Index (CWQI) suggested midstream water quality was poor in general, and 80% of annual calculations had a marginal grade. For aquatic organisms, ecological risks of Cu and Zn were high. For local residents, drinking water was generally safe, but continued monitoring is critical due to ongoing threats to water quality in these areas. [ABSTRACT FROM AUTHOR]

The phytoplankton (internal driving forces) and environmental variables that affect complex biochemical reactions (external driving forces) play an important role in regulating photosynthetic carbon fixation. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) exists in various phytoplankton species and is an important enzyme in the photosynthetic process. To investigate the phytoplankton composition (internal driving forces), we selected the functional gene of the Rubisco large subunit (rbcL) as the target gene for this study. Phytoplankton gross primary productivity was measured using light and dark biological oxygen demand bottles to assess the carbon sequestration potential. The fundamental environmental indicators were determined to analyze the mechanisms that drive the carbon fixation process. The correlation results indicated that green algae were only controlled by nitrate, and that diatoms were positively correlated with phosphate. The cluster analysis results demonstrated that nitrite was the major driver controlling phytoplankton primary productivity. During the wet seasons (spring and summer), the contribution of the planktonic community respiration to the carbon sequestration potential was higher than net primary productivity (NPP), followed by dissolved organic carbon and nitrate. During the dry season (autumn), NPP, total nitrogen, and nitrite ranked highest in terms of carbon sequestration potential. The contributions of green algae and diatoms to the carbon sequestration potential were temporally higher than those of cyanobacteria. The maximum carbon sequestration potential occurred during autumn because of diatom production and the function of phosphate, whereas the minimum carbon sequestration potential occurred in summer. Spatially, the upstream carbon sequestration potential was higher compared with downstream because of the effect (contribution) of cyanobacteria (Phormidium), diatoms (Surirella solea and Thalassiosira pseudonana), and environmental variable (nitrite). These findings provide a better understanding of the underlying mechanisms of phytoplankton productivity and the influences of environmental variables on carbon sequestration in urban river ecosystems. [ABSTRACT FROM AUTHOR]

Five common used green algae species, Chlorella vulgaris, Chlorococcum sp. GD, Parachlorella kessleri TY, Scenedesmus obliquus, and Scenedesmus quadricauda, were evaluated for their growth and nitrogen removal properties when being cultivated in synthetic wastewater with ammonium and nitrate as nitrogen sources. The five microalgae could adapt wastewater with different kinds of nitrogen sources, but the growth potential and nitrogen removal ability were species-dependent. Parachlorella kessleri TY cultivated in wastewater with ammonium and nitrate had higher biomass concentration of 2750 and 2765 mg L−1, respectively, compared to C. vulgaris, S. obliquus, and S. quadricauda. Chlorococcum sp. GD in wastewater with nitrate had the highest biomass concentration of 3095 mg L−1. Although all microalgae showed a good removal efficiency of nitrogen (ammonium: 85.30-97.03%; nitrate: 100%) after 7 days of cultivation, Chlorococcum sp. GD and P. kessleri TY removed 85-90.24% of ammonium and 100% of nitrate within 2-3 days, which was faster than the other three microalgae. It was also found that the growth and pollutant removal of microalgae in wastewater with nitrate was superior to those of microalgae in wastewater with ammonium. This was caused by the inhibitory effect of the low pH when microalgae were cultivated in wastewater with ammonium as the nitrogen source. Based on the results above, the growth and nitrogen removal was closely related to the microalgal species and the pH of the wastewater. [ABSTRACT FROM AUTHOR]

Arthrospira (Spirulina) platensis extract (APE) was used as a natural antioxidant in Chinese-style sausage during storage at 4 °C for 18 days. As compared to control, we examined the effect of APE on physical, chemical, microbiological, and sensory qualities of sausages, as well as on change in pH, color, thiobarbituric value (TBARS), volatile basic nitrogen (VBN), and total viable counts of mesophilic and psychrotrophic bacteria. The sensory qualities including color, aroma, taste, texture, and overall acceptability were evaluated. It was found that APE sausages displayed lower changes in pH, lightness (L*), redness (a*), yellowness (b*), TBARS value, and sensory attributes than control. However, there was no significant difference in VBN and microbiological status between APE and control sausages. Successful inhibition of lipid oxidation in samples was possible with the incorporation of APE in the refrigerated Chinese-style sausages. Our results suggest that the incorporation of APE into Chinese-style pork sausages enhance the antioxidant and maintains product quality. [ABSTRACT FROM AUTHOR]

Two chrysophytes, associated with mosses in Shanxi Province, China, were isolated from Haplocladium strictulum (Card.) Reim, and Timmiella anomala. Both of the Chrysophytes were successfully cultivated under axenic conditions. Morphological observations indicated that the two isolated Chrysophytes belong to the genus Poterioochromonas. However, no loricae or scales were detected around the cells. Based on phylogenetic analyses of SSU rRNA and COI genes, the two isolates were closely related, if not identical to P. malhamensis. It suggested that the loss of ability of these isolates of P. malhamensis to form a lorica may be related to living in association with mosses. The bryophyte may replace the role of the lorica on the algal cells by providing a protected micro-environment. As a result, the algae associated with these bryophytes lose their loricae which allows more light penetration for photosynthesis. [ABSTRACT FROM AUTHOR]

Removing phenol from wastewater has become a major challenge of international concern. Phytoremediation is a novel and eco-friendly method and is attracting an increasing amount of attention for treating phenol in wastewater. We studied the ability of Polygonum orientale, which is frequently present around water bodies and in wetlands in China, to phytoremediate phenol. We determined the inhibition concentration for phenol on P. orientale using emergency toxicology experiments and morphological observations. Isothermal and kinetic models were created to assess the adsorption process involved in phenol removal. Comparison tests in sterile conditions demonstrated that metabolic removal was the main way in which the phenol concentrations were decreased, and removal by adsorption played a smaller role. An orthogonal test was performed to determine the optimum conditions under which P. orientale will remove phenol, and these were found to be an initial phenol concentration of 5 mg L, 100 % natural light, and a 13-day treatment time. These results provide a theoretical basis for increasing our understanding of the mechanisms involved in the removal of phenol by P. orientale and will help in developing its application in the greening of urban areas to provide both phytoremediation and esthetic landscaping. [ABSTRACT FROM AUTHOR]

We prepared an ethanol extract from Laminaria japonica, and obtained five fractions from the extract using various solvents. We investigated the antibacterial activities of the fractions against Clavibacter michiganensis subsp. sepedonicus (Spieckermann & Kotthoff) Davis et al., the causal agent of bacterial ring rot of potato (BRR). Among all the fractions, the petroleum ether fraction showed the strongest ( P < 0.05) antibacterial activity against C. michiganensis subsp. sepedonicus. We analyzed the petroleum ether fraction to detect the components with antibacterial activity, and identified 24 compounds. The main constituents of the petroleum ether extract were esters (35.28 %) and acids (44.84 %). Cell membrane permeability assays, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed that the petroleum ether fraction caused drastic ultrastructural changes in the cells of the pathogen. The petroleum ether fraction caused envelope disruption, cell deformation, the separation of the cell wall from the cell membrane, and the formation of vacuoles. These results clearly indicate that the petroleum ether fraction obtained from L. japonica shows strong antibacterial activity against the causal agent of BRR. [ABSTRACT FROM AUTHOR]

Batrachospermum arcuatum Kylin is typically dioecious, although some monoecious specimens have been collected from four locations in North China. In this study, B. arcuatum populations, including monoecious and dioecious thalli, were collected from seven stream segments. The nuclear DNA internal transcribed spacer (ITS) region was sequenced for the seven populations, and a phylogenetic tree was constructed using Bayesian inference to assess intraspecific relationships. A haplotype network was also created. The ITS region in B. arcuatum from North China comprised 822-853 bp, with 10 haplotypes detected from the seven locations. The results of this study support the inclusion of monoecious individuals in the species B. arcuatum. [ABSTRACT FROM AUTHOR]

Macroalgae have received much attention for heavy metal removal in treatment of domestic wastewater. In this report, the uptake capacity of a common freshwater green alga, Cladophora fracta, for heavy metal ions (copper, zinc, cadmium, and mercury) was evaluated. The equilibrium adsorption capacities were 2.388 mg Cu, 1.623 mg Zn, 0.240 mg Cd, and 0.228 mg Hg per gram of living algae at 18°C and pH 5.0. The removal efficiency for Cu, Zn, Cd, and Hg were 99, 85, 97, and 98%, respectively. Greater removal efficiency was achieved when the concentrations of metal ions were at very low level. The results indicated that living algae are suitable for removal and recovery of heavy metal ions from aqueous solutions and can be a potential tool to treat industrial wastewater. [ABSTRACT FROM AUTHOR]

The phenology of Chara vulgaris was studied. The specimens were collected four times from April 2004 to January 2005 (one sampling per season). The water temperature, pH, dissolved oxygen, specific conductance, maximum width and maximum depth were monitored at every sampling time. Eighteen main morphological characteristics of the Chara vulgaris were also observed and measured under the microscope. The results showed that all the environmental factors had different seasonal patterns and some of the morphological characteristics had significant fluctuations, indicating differences in their seasonality. At the same time, some morphological characteristics were affected by the environmental parameters to some extent and the effect was primarily exhibited in its vegetative proportions; there was little effect on the sexual reproductive characteristics. Therefore, the relatively stable sexual reproductive characteristics can be used to identify the species. [ABSTRACT FROM AUTHOR]

Understanding the relative impact sizes of environmental factors and nutrients on the high annual variation of phytoplankton abundance in eutrophic rivers is important for aquatic ecosystem management efforts. In this study, we used phytoplankton dynamic datasets in the eutrophic Fenhe River to show the variations and drivers of phytoplankton abundance under complex, fluctuating environmental conditions during 2012–2017. The temporal and spatial variations of nutrients in the river depicted that the total phosphorus (TP) concentration was higher in the wet season and in downstream. There were increases in total nitrogen (TN) concentration in the normal season and in upstream. The structural equation model (SEM) showed that the phytoplankton abundance increased during the wet season despite the decrease in the TN:TP ratio and was reduced upstream due to the highest TN:TP ratio. Among the environmental variables, water temperature (WT) was an important predictor and positively correlated temporally and spatially to phytoplankton. The interaction of nutrients with the phytoplankton community at different temperature levels indicated that different phytoplankton groups have different nutrient requirements. We can conclude that enhances in temperature and TP concentration will significantly increase phytoplankton abundance and dominance of cyanobacteria and green algae in the future, whereas there was insignificant effect on diatoms. These data indicated that temperature and TP content were the important abiotic factors influencing the phytoplankton growth of the water body, which could provide a reference for the evaluation of environmental alterations in the future. [ABSTRACT FROM AUTHOR]

In this paper, the algal cell density of cyanobacteria, green algae, and diatoms and their responses to the hydrochemical factors were analyzed to reveal the structural characteristics of water quality in an urban river. A total of nine sampling sites from upstream to downstream was explored in our study. At each site, the density of algae was identified every week during the wet season (June-October) from 2012 to 2017, and in situ detection was used for the relative 11 hydrochemical variables. The temporal and spatial characteristics of 14 variables were analyzed using a heatmap coupled with the cluster analysis method. The trend of each parameter was analyzed using the smoothing method with locally weighted regression. The nonmetric multidimensional scaling method was employed to detect the temporal and spatial similarities among algae along hydrochemical gradients. The responses of algal density to hydrochemical variables were analyzed using a redundancy analysis. The results showed that the water temperature (Wtemp), pH, dissolved oxygen (DO), cyanobacteria, and diatoms exhibited significant declining trends, and significant increasing trends were shown in the permanganate index, chemical oxygen demand, total nitrogen, ammonia nitrogen, and total phosphorus; the cyanobacteria exhibited certain differences with green algae and diatoms in summer and the downstream areas of the river. The temporal-spatial homogeneity of algal to hydrochemical variables showed the key influencing factors of Wtemp for cyanobacteria density, chlorophyll for green algae density, DO, and pH for diatoms. The results presented here are valuable for deepening our understanding of river ecosystem evaluations and effective environmental management, as well as an important reference for the sustainable development of aquatic biological resources. [ABSTRACT FROM AUTHOR]

1,4-Dichlorobenzene (1,4-DCB) is a common organic contaminant in water. To determine the effects of this contaminant on photosynthesis in the freshwater alga Chlorella pyrenoidosa, algal cells were treated with 1,4-DCB at different concentrations for various times, and their photosynthetic pigment contents and chlorophyll fluorescence traits were analyzed. The results showed that 1,4-DCB exerted toxic effects on photosynthesis in C. pyrenoidosa, especially at concentrations exceeding 10 mg/L. The inhibitory effects of 1,4-DCB were time- and concentration-dependent. After treatment with 1,4-DCB (≥10 mg/L), the contents of photosynthetic pigments decreased significantly, the photosystem II reaction center was irreversibly damaged, and the quantum yield of photosystem II decreased significantly. Also, there were sharp decreases in the efficiency of photosynthetic electron transport and energy conversion. Photosystem II became overloaded as the amount of excitation energy distributed to it increased. All of these events weakened the photochemical reaction, and ultimately led to serious inhibition of photosynthesis. [ABSTRACT FROM AUTHOR]