Diversity Patterns of Eukaryotic Phytoplankton in the Medog Section of the Yarlung Zangbo River.

As one of the important biodiversity conservation areas in China, the ecosystem in the lower reaches of the Yarlung Zangbo River is fragile, and is particularly sensitive to global changes. To reveal the diversity pattern of phytoplankton, the metabarcode sequencing was employed in the Medog section of the lower reaches of the Yarlung Zangbo River during autumn 2019 in present study. The phytoplankton assemblies can be significantly divided into the main stem and the tributaries; there are significant differences in the phytoplankton biomass, alpha and beta diversity between the main stem and the tributaries. While both the main stem and the tributaries are affected by dispersal limitation, the phytoplankton assemblages in the entire lower reaches are primarily influenced by heterogeneous selection. Community dissimilarity and assembly process were significantly correlated with turbidity, electrical conductivity, and nitrogen nutrition. The tributaries were the main source of the increase in phytoplankton diversity in the lower reaches of the Yarlung Zangbo River. Such diversity pattern of phytoplankton in the lower reach may be caused by the special habitat in Medog, that is, the excessive flow velocity, and the significant spatial heterogeneity in physical and chemical factors between stem and tributaries. Based on the results and conclusions obtained in present study, continuous long-term monitoring is essential to assess and quantify the impact of global changes on phytoplankton.

Reassessment of suitable markers for taxonomy of Chaetophorales (Chlorophyceae, Chlorophyta) based on chloroplast genomes.

Filamentous green algae Chaetophorales present numerous taxonomic problems as many other green algae. Phylogenetic analyses based on nuclear genes have limited solutions. Studies with appropriate chloroplast molecular markers may solve this problems; however, suitable molecular markers for the order Chaetophorales are still unknown. In this study, 50 chloroplast genomes of Chlorophyceae, including 15 of Chaetophorales, were subjected to single protein-coding gene phylogenetic analyses, and substitution rate and evolutionary rate assays, and PCR amplification verification was conducted to screen the suitable molecular markers. Phylogenetic analyses of three chloroplast representative genes (psaB, tufA, and rbcL) amplified from 124 strains of Chaetophorales showed that phylogenetic relationships were not improved by increasing the number of samples, implying that the genes themselves, rather than limited samples, were the reason for the unsupported Topology I. Seven genes (atpF, atpI, ccsA, cemA, chlB, psbB, and rpl2) with robust support were selected to be the most suitable molecular markers for phylogenetic analyses of Chaetophorales, and the concatenated seven genes could replace the time-consuming and labor-intensive phylogenetic analyses based on chloroplast genome to some extent. To further solve the taxonomic problems of Chaetophorales, suitable chloroplast markers combined with more taxon-rich approach could be helpful and efficient.

Watanabeales ord. nov. and twelve novel species of Trebouxiophyceae (Chlorophyta).

The Trebouxiophyceae include Chlorellales, Prasiolales, Trebouxiales, Microthamniales, and numerous members for which taxonomic locations have not been determined. The Watanabea clade is a group in the Trebouxiophyceae of Chlorella-like taxa, which are predominantly solitary and terrestrial. With the increase in descriptions of new species within the Watanabea clade in recent years, it is necessary to define the boundary and taxonomic status of the clade. In this study, nineteen strains of terrestrial algae collected from China were investigated based on molecular and morphological data, involving phylogenetic analyses, light and electron microscopy, and ITS-2 secondary structures. These 19 strains were described as five known species and 12 novel ones. Based on the consistent topological structures of the phylogenetic analyses for three taxonomic levels (the core Chorophyta, Trebouxiophyceae based on 18S sequences, Watanabeales and Symbiochloris based on 18S, 5.8S, ITS2 and rbcL gene sequences) and common morphological characteristics, especially the key phenotypic feature of unequally sized autospores, the Watanabea clade was defined as a new order, Watanabeales ord. nov., with one family, Watanabeaceae fam. nov. The boundary of Watanabeales was delineated and included the genera Chloroidium, Calidiella, Jaagichlorella, Kalinella, Massjukichlorella, Mysteriochloris, Polulichloris, Phyllosiphon, Watanabea, and Viridiella. Symbiochloris did not belong to Watanabeales according to the phylogenetic analyses and the reproduction by equal-sized autospores, aplanospores, or zoospores. The Watanabeales were separated into four groups during the phylogenetic analyses, but no regular differences in habitats or morphology could be used as the morphological basis to split Watanabeales into the four groups.

Taxonomic scheme of the order Chaetophorales (Chlorophyceae, Chlorophyta) based on chloroplast genomes.

BACKGROUND: Order Chaetophorales currently includes six families, namely Schizomeridaceae, Aphanochaetaceae, Barrancaceae, Uronemataceae, Fritschiellaceae, and Chaetophoraceae. The phylogenetic relationships of Chaetophorales have been inferred primarily based on short and less informative rDNA sequences. This study aimed to phylogenetically reconstruct order Chaetophorales and determine the taxonomic scheme, and to further understand the evolution of order Chaetophorales. RESULTS: In the present study, seven complete and five fragmentary chloroplast genomes were harvested. Phylogenomic and comparative genomic analysis were performed to determine the taxonomic scheme within Chaetophorales. Consequently, Oedogoniales was found to be a sister to a clade linking Chaetophorales and Chaetopeltidales. Schizomeriaceae, and Aphanochaetaceae clustered into a well-resolved basal clade in Chaetophorales, inconsistent with the results of phylogenetic analysis based on rDNA sequences. Comparative genomic analyses revealed that the chloroplast genomes of Schizomeriaceae and Aphanochaetaceae were highly conserved and homologous, highlighting the closest relationship in this order. Germination types of zoospores precisely correlated with the phylogenetic relationships. CONCLUSIONS: chloroplast genome structure analyses, synteny analyses, and zoospore germination analyses were concurrent with phylogenetic analyses based on the chloroplast genome, and all of them robustly determined the unique taxonomic scheme of Chaetophorales and the relationships of Oedogoniales, Chaetophorales, and Chaetopeltidales.

Four New Members of Foliicolous Green Algae Within the Watanabea Clade (Trebouxiophyceae, Chlorophyta) from China.

Members of the Watanabea clade of Trebouxiophyceae are genetically diverse and widely distributed in all kinds of habitats, especially in most terrestrial habitats. Ten new strains of terrestrial algae isolated from the tropical rainforest in China, and four published strains were investigated in this study. Morphological observation and molecular phylogenetic analyses based on the 18S, ITS, rbcL, and tufA genes were used to identify the new strains. Four previously described species were reinvestigated to supplement molecular data and autospores' morphological photographs. The phylogenetic analyses based on 18S only, the concatenated dataset of 18S and ITS, as well as the concatenated dataset of rbcL and tufA, showed the same phylogenetic positions and relationships of these new strains. According to the phylogenetic analysis and morphological comparisons results, we described these 10 strains as four new members within the Watanabea clade, Polulichloris yunnanensis sp. nov., Polulichloris ovale sp. nov., Massjukichlorella orientale sp. nov., and Massjukichlorella minus sp. nov., and two known species, Massjukichlorella epiphytica, and Mysteriochloris nanningensis. Additionally, we provide strong evidence proving that Phyllosiphon, Mysteriochloris, Polulichloris, and Desertella all reproduce through unequal sized autospores.

Chlorocladiella gen. nov. (Pithophoraceae, Cladophorales, Chlorophyta), Including Four New Species From Various Freshwater Habitats in China.

Samples of Pithophoraceae, collected in diverse freshwater and damp terrestrial habitats from tropical and subtropical China, were characterized morphologically and ultrastructurally, and their phylogenetic position was determined based on nuclear ribosomal DNA sequences. Our phylogenetic analysis resolved a novel lineage of Pithophoraceae, sister to Aegagropilopsis. Based on our phylogenetic results, morphological observations and comparative rDNA ITS2 secondary structure analysis, we propose Chlorocladiella gen. nov., characterized by a well-developed system of prostrate filaments, and describe four new species, C. cochlea sp. nov., C. erecta sp. nov., C. medogensis sp. nov., and C. pisformis sp. nov. Two species were found growing on damp soil, which is an unusual habitat for cladophoralean green algae, indicating that the diversity of Cladophorales in terrestrial habitats may be greater than currently recognized.

Molecular phylogeny and taxonomy of the genus Chaetophora (Chlorophyceae, Chlorophyta), including descriptions of Chaetophoropsis aershanensis gen. et sp. nov.

The broadly defined genus Chaetophora consisted of species with minute, uniseriate branching filaments enveloped in soft or firm mucilage forming macroscopic growths that are spherical, hemispherical, and tubercular or arbuscular, growing epiphytically on freshwater aquatic plants and other submerged surfaces in standing or fast-flowing water. Recent molecular analyses clearly showed that this genus was polyphyletic. In this study, eight strains of Chaetophora and three strains of Stigeoclonium were identified and successfully cultured. In combination with the morphological data, a concatenated data set of four markers (18S + 5.8S + ITS2+ partial 28S rDNA) was also used to determine their taxonomic relationships and phylogenetic positions. The molecular analysis resolved the broadly defined Chaetophora to at least two genera. Species with a globose thallus of genus Chaetophora formed a separate monophyletic clade, which clearly separated from, a type of lobe-form Chaetophora species. Therefore, we propose to erect a new genus, Chaetophoropsis, which includes all globose species of the Chaetophora. Chaetophoropsis aershanensis was determined to be a new species, based on its special characteristic of profuse long rhizoids. Stigeoclonium polyrhizum, as the closest relative to Chaetophoropsis, revealed its distant relationships to other species of Stigeoclonium. A globose thallus with a thick, soft mucilage matrix, and special rhizoidal branches lent further support to the placement of S. polyrhizum in the genus Chaetophoropsis and had the closest relationship to C. aershanensis. Taxonomic diversity was proven by distinctive morphological differences and by phylogenetic divergence in the broadly defined Chaetophora identified herein.

Morphology and molecular phylogeny of coccoid green algae Coelastrella sensu lato (Scenedesmaceae, Sphaeropeales), including the description of three new species and two new varieties.

The genus Coelastrella was established by Chodat (Bull. Soc. Bot. Geneve, 13 [1922] 66), and was characterized as being unicellular or in few-celled aggregations with many longitudinal ribs on the cell wall. Many species of this genus showed strong ability to accumulate carotenoids and oils, so they have recently attracted much attention from researchers due to its potential applicability in the energy and food industries. In this study, a total of 23 strains of Coelastrella were sampled from China, and three new species and two new varieties were described: C. thermophila sp. nov., C. yingshanensis sp. nov., C. tenuitheca sp. nov., C. thermophila var. globulina var. nov., C. rubescens var. oocystiformis var. nov. Besides 18S rDNA and ITS2 sequences, we have newly sequenced the tufA gene marker for this taxon. Phylogenetic analysis combined with morphological studies revealed four morphotypes within the Coelastrella sensu lato clade, which contained the morphotype of original Coelastrella, original Scotiellopsis, Asterarcys, and morphotype of C. vacuolata and C. tenuitheca sp. nov. The relationships between morphological differences and phylogenic diversity based on different markers were discussed. Our results support that 18S rDNA was too conserved to be used a species-specific or even a genus-specific marker in this clade. The topology of tufA gene-based phylogenetic tree had a better match with the morphological findings.

Classification of planctonema-like algae, including a new genus Planctonemopsis gen. nov., a new species Planctonema gelatinosum sp. nov. and a reinstated genus Psephonema (Trebouxiophyceae, Chlorophyta).

Planctonema-like species consist of planktonic green algae and are found throughout the world. Their characteristic morphology, which includes short and slender filaments consisting of side-by-side or distant cylindrical cells enclosed in a fine and hyaline sheath, makes them easily distinguishable. To date, Planctonema lauterbornii was the only taxon accepted for this group. However, descriptions from different materials have revealed notable morphological differences, including the presence/absence of a pyrenoid, a mucilage sheath and an apical thickening of the cell wall. In this study, six strains of Planctonema-like species were identified and successfully cultured in the laboratory. We used a molecular approach to determine their taxonomic relationships and phylogenetic positions. The molecular analysis resolved them to at least three genera. The genus Planctonema was positioned in Trebouxiophyceae as an incertae sedis taxon that is closely related to Oocystaceae and was divided into two species. Planctonema gelatinosum was determined to be a new species with approximately twice the width and a thicker mucilage sheath, which differentiated it from the type species Planctonema lauterbornii. The genus Psephonema was reinstated based on 1.5-2 times length-width ratio than Planctonema and the big difference on the rbcL cpDNA gene marker and an intron insertion in the 18S rDNA. A new genus, Planctonemopsis, which represents the pyrenoid-present strains among the Planctonema-like species, was established. Planctonemopsis was positioned within Oocystaceae as a new clade and is distantly related to the other two genera. Taxonomic diversity was proven by distinctive morphological differences and phylogenetic divergence in the Planctonema-like group identified herein.

Lakes-scale pattern of eukaryotic phytoplankton diversity and assembly process shaped by electrical conductivity in central Qinghai-Tibet Plateau.

Phytoplankton are the main primary producers in aquatic ecosystems and play an important role in food web and geochemical cycles. Its diversity, community structure, and assembly process are influenced by several factors. Alpine lake ecosystems are relatively weak and extremely sensitive to global climate change. However, the impact of climate change on phytoplankton in Qinghai-Tibet Plateau lakes and their responses are still unclear. In this study, we analyzed the diversity, environmental drivers, and assembly process of phytoplankton community in the central QTP lakes. The phytoplankton of these lakes can be primarily distinguished into freshwater and brackish types, with significant differences in species diversity and community dissimilarity. Both shared nearly same key environmental factors that significantly affecting phytoplankton such as EC, and brackish lakes were also positively correlative with TN. Stochastic process was predominant in phytoplankton assembly. Additionally, freshwater and brackish lakes were dominated by dispersal limitation and heterogeneous selection respectively. Alpine lakes had significant EC thresholds, and their diversity and assembly processes changed significantly around the thresholds. The present findings have important implications for understanding and predicting the response of lake phytoplankton communities to climate change and for making decisions to protect the ecological resources of alpine lakes.

Morphology and Molecular Phylogeny of the Genus Stigeoclonium (Chaetophorales, Chlorophyta) from China, Including Descriptions of the Pseudostigeoclonium gen. nov.

Stigeoclonium is a genus of green algae that is widely distributed in freshwater habitats around the world. The genus comprises species with variously developed prostrates and erect systems of uniseriate branched filaments and grows attached to a wide range of different surfaces. It holds significant promise for applications in water quality indicators, sewage treatment, and the development of high-value-added products. Nevertheless, our comprehension of Stigeoclonium remains unclear and perplexing, particularly regarding its fundamental systematic taxonomy. Recent molecular analyses have revealed that the morphologically well-defined genus Stigeoclonium is polyphyletic and requires taxonomic revision. Phylogenetic analysis based on a single molecular marker and limited samples is insufficient to address the polyphyletic nature of Stigeoclonium. In the present study, 34 out of 45 strains of Stigeoclonium were newly acquired from China. Alongside the morphological data, a concatenated dataset of three markers (18S rDNA + ITS2 + tufA) was utilized to determine their molecular phylogeny. The phylogenetic analysis successfully resolved the broadly defined Stigeoclonium into three robustly supported clades (Stigeoclonim tenue clade, S. farctum clade, and S. helveticum clade). The morphological characteristics assessment results showed that the cell type of the main axis-producing branch, considered a crucial morphological characteristic of the Stigeoclonium taxonomy, did not accurately reflect the real phylogeny of the genus. A new taxonomical classification of the genus Stigeoclonium was proposed based on zoospores' germination types, which aligned well with the phylogenetic topologies. Species where zoospores showed erect germination (S. helveticum clade) formed a distinct monophyletic clade, clearly separated from the other two clades, with zoospores showing prostrate germination or pseudo-erect germination. Consequently, a new genus, Pseudostigeoclonium gen. nov., is suggested to include all species in the broadly defined Stigeoclonium with zoospores with erect germination. The taxonomic diversity is supported by distinctive morphological differences and phylogenetic divergence within the broadly defined Stigeoclonium identified in this study. Further evaluation of the genus Stigeoclonium is necessary, especially via examining additional specimens and re-evaluating morphological characters under precisely defined laboratory conditions.

Phyllosphere eukaryotic microalgal communities in rainforests: Drivers and diversity.

Phyllosphere algae are common in tropical rainforests, forming visible biofilms or spots on plant leaf surfaces. However, knowledge of phyllosphere algal diversity and the environmental factors that drive that diversity is limited. The aim of this study is to identify the environmental factors that drive phyllosphere algal community composition and diversity in rainforests. For this purpose, we used single molecule real-time sequencing of full-length 18S rDNA to characterize the composition of phyllosphere microalgal communities growing on four host tree species (Ficus tikoua, Caryota mitis, Arenga pinnata, and Musa acuminata) common to three types of forest over four months at the Xishuangbanna Tropical Botanical Garden, Yunnan Province, China. Environmental 18S rDNA sequences revealed that the green algae orders Watanabeales and Trentepohliales were dominant in almost all algal communities and that phyllosphere algal species richness and biomass were lower in planted forest than in primeval and reserve rainforest. In addition, algal community composition differed significantly between planted forest and primeval rainforest. We also found that algal communities were affected by soluble reactive phosphorous, total nitrogen, and ammonium contents. Our findings indicate that algal community structure is significantly related to forest type and host tree species. Furthermore, this study is the first to identify environmental factors that affect phyllosphere algal communities, significantly contributing to future taxonomic research, especially for the green algae orders Watanabeales and Trentepohliales. This research also serves as an important reference for molecular diversity analysis of algae in other specific habitats, such as epiphytic algae and soil algae.

Seven newly sequenced chloroplast genomes from the order Watanabeales (Trebouxiophyceae, Chlorophyta): Phylogenetic and comparative analysis.

The little-known order Watanabeales currently includes 10 genera with Chlorella-like species that reproduce by unequal-sized autospores and are predominantly solitary or terrestrial. The taxonomic scheme of Watanabeales has only been primarily inferred by short and less informative rDNA phylogenetic analysis. In the present study, seven newly sequenced genomes and one reported chloroplast genome representing the existing major branches of Watanabeales were harvested to phylogenetically reconstruct this order and to further understand its evolution. All chloroplast genomes of Watanabeales ranging from 133 to 274 kb were circular mapping and lacked a quadripartite structure. The chloroplast genome size, GC content, number of introns, and length of intergenic region proportion of the Watanabeales showed consistent trends, with Calidiella yingdensis D201 and Kalinella pachyderma 2601 having the lowest and highest values, respectively, echoing the positive correlation between organismal size and genome size. Phylogenetic analysis of Watanabeales based on 76 protein-coding genes coupled with the establishment of various complex analytical methods determined the unique robust taxonomic scheme which was incongruent with rDNA. Comparative genomic analyses revealed that the chloroplast genomes of Watanabeales accounted for numerous complex rearrangements and inversions which indicated high cryptic diversity. Substitution rate estimation indicated that the chloroplast genomes of Watanabeales were under purifying selection and similar evolutionary pressure and supported the view that genus Symbiochloris should be excluded from Watanabeales. Our results enrich the chloroplast genome resources of Watanabeales, clarify the phylogenetic status of species within this order, and provide more reference information for subsequent taxonomic and phylogenetic study.

Phylotranscriptomic and Evolutionary Analyses of the Green Algal Order Chaetophorales (Chlorophyceae, Chlorophyta).

Considering the phylogenetic differences in the taxonomic framework of the Chaetophorales as determined by the use of nuclear molecular markers or chloroplast genes, the current study was the first to use phylotranscriptomic analyses comparing the transcriptomes of 12 Chaetophorales algal species. The results showed that a total of 240,133 gene families and 143 single-copy orthogroups were identified. Based on the single-copy orthogroups, supergene analysis and the coalescent-based approach were adopted to perform phylotranscriptomic analysis of the Chaetophorales. The phylogenetic relationships of most species were consistent with those of phylogenetic analyses based on the chloroplast genome data rather than nuclear molecular markers. The Schizomeriaceae and the Aphanochaetaceae clustered into a well-resolved basal clade in the Chaetophorales by either strategy. Evolutionary analyses of divergence time and substitution rate also revealed that the closest relationships existed between the Schizomeriaceae and Aphanochaetaceae. All species in the Chaetophorales exhibited a large number of expanded and contracted gene families, in particular the common ancestor of the Schizomeriaceae and Aphanochaetaceae. The only terrestrial alga, Fritschiella tuberosa, had the greatest number of expanded gene families, which were associated with increased fatty acid biosynthesis. Phylotranscriptomic and evolutionary analyses all robustly identified the unique taxonomic relationship of Chaetophorales consistent with chloroplast genome data, proving the advantages of high-throughput data in phylogeny.

Taxonomic study of a novel terrestrial alga, Spongiosarcinopsisqinghaiensis sp. nov. (Protosiphonaceae, Chlorophyta), from the Qinghai-Tibet Plateau.

There is only one species of Spongiosarcinopsis in the literature currently. It was found in gray soil in Russia for the first time. According to molecular data analysis results, the isolated algal strain is most closely related to Spongiosarcinopsisterrestris. Unlike Spongiosarcinopsisterrestris, the isolated strain was found on soil surfaces at high altitudes, the young vegetative cell is spherical, vegetative cells are relatively large, and pyrenoids are generally fewer. In view of such morphological differences, phylogenetic analysis results, and comparison of ITS2 secondary structure and ultrastructure, the strain isolated in the present study was proposed to be a novel species.

Morphology and Molecular Phylogeny of Genus Oedogonium (Oedogoniales, Chlorophyta) from China.

Oedogoniales comprises the three genera Oedogonium, Oedocladium, and Bulbochaete, which include more than 600 described species. The classification of Oedogoniaceae is currently based on morphology, and the complicated morphological characteristics make species identification difficult, with the limited molecular data also restricting the phylogenetic analysis. In the present study, we collected 47 Oedogonium specimens from China and sequenced 18S rDNA, ITS2, ITS (ITS1 + 5.8S + ITS2), and rbcL sequences to conduct phylogenetic analyses. We selected nine morphological characteristics, most of which were considered important in traditional systematics, for comparison with the molecular phylogeny results. All the topologies based on different datasets showed similar results; Oedogonium was a paraphyletic group, and Oedocladium and Bulbochaete clustered with Oedogonium. The morphological characteristics matching the phylogenetic results showed that the types of sexual differentiation, characteristics of the oogonium (including shape, types of aperture, and ornamentation of oospore wall), division types of antheridial, and number of sperm of each antheridial, which are considered the most important morphological characteristics in traditional taxonomy of Oedogonium, did not form monophyletic lineages respectively, indicating that traditional systematics may not reflect the real phylogeny of the genus Oedogonium. In addition, a new taxonomical classification of the genus Oedogonium was presented according to the shapes of basal cells, which matched well with the phylogenetic topologies. In addition, we propose to divide the genus Oedogonium into two sections, section Globosum and section Elongatum, representing the species with spherical or sub-hemispherical basal cells and elongated basal cells, respectively.

Six Newly Sequenced Chloroplast Genomes From Trentepohliales: The Inflated Genomes, Alternative Genetic Code and Dynamic Evolution.

Cephaleuros is often known as an algal pathogen with 19 taxonomically valid species, some of which are responsible for red rust and algal spot diseases in vascular plants. No chloroplast genomes have yet been reported in this genus, and the limited genetic information is an obstacle to understanding the evolution of this genus. In this study, we sequenced six new Trentepohliales chloroplast genomes, including four Cephaleuros and two Trentepohlia. The chloroplast genomes of Trentepohliales are large compared to most green algae, ranging from 216 to 408 kbp. They encode between 93 and 98 genes and have a GC content of 26-36%. All new chloroplast genomes were circular-mapping and lacked a quadripartite structure, in contrast to the previously sequenced Trentepohlia odorata, which does have an inverted repeat. The duplicated trnD -GTC, petD, and atpA genes in C. karstenii may be remnants of the IR region and shed light on its reduction. Chloroplast genes of Trentepohliales show elevated rates of evolution, strong rearrangement dynamics and several genes display an alternative genetic code with reassignment of the UGA/UAG codon presumably coding for arginine. Our results present the first whole chloroplast genome of the genus Cephaleuros and enrich the chloroplast genome resources of Trentepohliales.

Chloroplast genome analysis of Chrysotila dentata.

Chrysotila dentata is an ecologically important marine alga contributing to the coccolith formation. In this study, a complete chloroplast (cp DNA) genome of Chrysotila dentata was sequenced by using Illumina Hiseq and was analyzed with the help of a bioinformatics tool CPGAVAS2. The circular chloroplast genome of Chrysotila dentata has a size of 109,017 bp with two inverted repeats (IRs) regions (4513 bp each) which is a common feature in most land plants and algal species. The Chrysotila dentata cp genome consists of 61 identified protein-coding genes, 30 tRNA genes and 6 rRNAs with 21 microsatellites. The phylogenetic relationship with other select algal species revealed a close phylogeny of Chrysotila dentata with Phaeocystis antarctica. This is the first report of the cp genome analysis of genus Chrysotila and the results from this study will be helpful for understanding the genetic structure and function of chloroplast in other species of Chrysotila.