Diverse Dinoflagellate Research Articles

Abundance and diversity of diatoms and dinoflagellates in an embayment off Central Chile (30°S): evidence of an optimal environmental window driven by low and high frequency winds

Abundance and diversity of diatoms and dinoflagellates in an embayment off Central Chile (30°S): evidence of an optimal environmental window driven by low and high frequency winds

Biodiversity of microorganisms in the Baltic Sea: the power of novel methods in the identification of marine microbes.

Until recently, the data on the diversity of the entire microbial community from the Baltic Sea were relatively rare and very scarce. However, modern molecular methods have provided new insights into this field with interesting results. They can be summarized as follows. (i) Although low salinity causes a reduction in the biodiversity of multicellular species relative to the populations of the North-East Atlantic, no such reduction occurs in bacterial diversity. (ii) Among cyanobacteria, the picocyanobacterial group dominates when considering gene abundance, while filamentous cyanobacteria dominate in means of biomass. (iii) The diversity of diatoms and dinoflagellates is significantly larger than described a few decades ago; however, molecular studies on these groups are still scarce. (iv) Knowledge gaps in other protistan communities are evident. (v) Salinity is the main limiting parameter of pelagic fungal community composition, while the benthic fungal diversity is shaped by water depth, salinity, and sediment C and N availability. (vi) Bacteriophages are the predominant group of viruses, while among viruses infecting eukaryotic hosts, Phycodnaviridae are the most abundant; the Baltic Sea virome is contaminated with viruses originating from urban and/or industrial habitats. These features make the Baltic Sea microbiome specific and unique among other marine environments.

Variability in Paralytic Shellfish Toxin Profiles and Dinoflagellate Diversity in Mussels and Seawater Collected during Spring in Korean Coastal Seawater.

Paralytic shellfish toxins (PSTs) are potent neurotoxins produced by certain microalgae, particularly dinoflagellates, and they can accumulate in shellfish in coastal seawater and thus pose significant health risks to humans. To explore the relationship between toxicity and PST profiles in seawater and mussels, the spatiotemporal variations in PST concentrations and profiles were investigated along the southern coast of Korea under peak PST levels during spring. Seawater and mussel samples were collected biweekly from multiple stations, and the toxin concentrations in the samples were measured. Moreover, the dinoflagellate community composition was analyzed using next-generation sequencing to identify potential PST-producing species. The PST concentrations and toxin profiles showed substantial spatiotemporal variability, with GTX1 and GTX4 representing the dominant toxins in both samples, and C1/2 tending to be higher in seawater. Alexandrium species were identified as the primary sources of PSTs. Environmental factors such as water temperature and salinity influenced PST production. This study demonstrates that variability in the amount and composition of PSTs is due to intricate ecological interactions. To mitigate shellfish poisoning, continuous monitoring must be conducted to gain a deeper understanding of these interactions.

Interaction patterns and assembly mechanisms of dinoflagellates and diatoms in a coastal bay suffering from long-term eutrophication.

Dinoflagellates and diatoms are highly prevalent and ecologically important phytoplankton in coastal waters, greatly contributing to primary productivity in marine ecosystems. Although their composition and diversity have been extensively elucidated in the open ocean, their interaction patterns and community assembly in long-term eutrophic coastal waters remain poorly understood. This investigation aimed to elucidate the seasonal successional patterns of dinoflagellates and diatoms by 18S rRNA gene amplicon sequencing in a semi-enclosed bay. The results revealed that dinoflagellate and diatom communities have pronounced seasonal succession patterns, which are primarily associated with temperature. Furthermore, the most prevalent species throughout the year were Heterocapsa rotundata and Skeletonema costatum. Moreover, the assembly of dinoflagellate and diatom communities was mainly dominated by stochastic processes, with drift being the major factor. The co-occurrence of dinoflagellates and diatoms showed seasonal patterns, with the highest interactions observed in autumn. In addition, interactions of Syndiniales with dinoflagellates and diatoms highlighted the roles of parasites in eutrophic conditions. Flavobacteriaceae and Rhodobacteraceae are the bacterial taxa that most frequently interacted with dinoflagellates and diatoms, with interactions between dinoflagellates and bacteria being more complex than those between diatoms and bacteria. Overall, this study provides results that deepen our understanding of the phytoplankton dynamics in coastal eutrophic waters.IMPORTANCEDinoflagellates and diatoms are major phytoplankton groups in coastal waters. The composition and diversity of dinoflagellates and diatoms in the open ocean have been well documented; however, it remains uncertain to what extent their adaptation to long-term eutrophic conditions influences their response to environmental disturbances. Here, we investigated the interactions and assembly processes of dinoflagellates and diatoms in a eutrophic bay throughout the whole year. Our findings revealed that interactions between dinoflagellates and diatoms are primarily shaped by seasonal transitions, while prolonged eutrophic conditions tend to amplify stochastic processes in community assembly. These findings provide novel perspectives on the influence of long-term eutrophication on phytoplankton dynamics within eutrophic waters.

Succession of phytoplankton communities from macro-scale to micro-scale in coastal waters of Qinhuangdao, China

The coastal area of Qinhuangdao, particularly the Changli Gold Coast Nature Reserve, is experiencing ecological degradation and frequent Harmful Algal Blooms (HABs). This study focuses on the changing phytoplankton communities in these coastal waters, examining them from both a macroscopic and microscopic perspective. Utilizing microscopy, molecular techniques, and pigment analysis, seasonal shifts were observed, with diatoms predominating in June and July, and dinoflagellates in August. Our morphological examination enabled the classification of 89 species into four distinct groups. The species Paralia sulcata and Pseudo-nitzschia pungens were most abundant in early summer, while Tripos furca, a dinoflagellate, dominated in August. This indicates a shift in phytoplankton communities due to environmental factors such as phosphate deficiency and high nitrogen/phosphorus ratios. Additionally, the study notes the impact of reduced river runoff and reintroduction of scallop farming contributing to nitrogen-rich eutrophication in August. Molecular analysis revealed a disparity between microscopic observations and the prevalence of Teleaulax blooms during early summer. Elevated concentrations of TN and DOC, coupled with limited water exchange, emerged as primary factors contributing to their occurrence. Sediment analysis revealed a high diversity but low abundance of dinoflagellates in August, with a significant presence of harmful species. The study highlights the shift from diatoms to harmful dinoflagellate populations, exacerbated by eutrophication and pollution, leading to HABs. These findings provide a theoretical basis for understanding toxic algal blooms and are crucial for environmental agencies in developing strategies to protect and sustainably develop offshore environments.

Monthly Variations of Dinoflagellates in Relation to the Water Parameters Along Purnagad Estuary, Ratnagiri, Maharashtra, India

Water samples were collected from Purnagad estuary, southwest coast of India. The monthly surface water sampling was carried out during high tide to find out the variations in physicochemical parameters and distribution of dinoflagellates. Samples were collected for one year period during 2022–2023. Dinoflagellates and water quality parameters were investigated to changes of dinoflagellates community. Variation in atmospheric temperature 21.9 - 37.2 0C, water temperatures varied from 25.4 - 37 0C, salinity varied from 0-37.6 psu, pH ranges between 7-8.8, dissolved oxygen 3.2-10.8 mgl-1, nitrate varied from 0.1747 - 0.1796 mgl-1, nitrite concentration varied from 0.0076 - 0.0228 mgl-1, phosphate values varied from 0.1038 mgl-1 to 0.3899 mgl-1, Silicate was varied from 0.0050 - 0.6031 mgl-1. A quantitative approach was employed, involving the collection of quantitative data through field sampling and laboratory analysis. During the study 22 species of dinoflagellates were encountered among which Ceratium fusus was dominant. Relatively high density and diversity of dinoflagellates were discovered in May as compared to the other months. Temperature showed a positive correlation with the dinoflagellate community showing its importance in dinoflagellate growth.

Diversity and biogeography of dinoflagellates in the Kuroshio region revealed by 18S rRNA metabarcoding

Dinoflagellate is one of the most diverse and pervasive protists and a fundamental player in the marine food web dynamics and biogeochemical cycles. While possessing different nutritional strategies from purely autotrophy or heterotrophy to mixotrophy, some of them are also known as toxic harmful algal bloom (HAB) formers over the world. Despite their ordinariness, their diversity and biogeography are understudied in the open ocean compared with coastal region. As the first metabarcoding survey covering the Kuroshio current region from the offshore of Okinawa to the south of Honshu, we investigated the distribution of free-living dinoflagellates using the hypervariable V4 and V9 regions on 18S rRNA and their relation to ambient environments influenced by this oligotrophic but highly productive current in the northwest Pacific Ocean. We observed community structures differentiated by depth and nutrient concentrations. Most species annotated are autotrophic or mixotrophic and had a distribution correlated to warmer surface water, whereas heterotrophic species correlated to high nutrient levels or deeper layer. Our results also confirmed the overall high genetic diversity of dinoflagellates that decreased with depth and onshore. Most species present at stations offshore, and the relative abundance of HAB assemblages was lower at nutrient-rich stations on the continental shelf than stations influenced by the Kuroshio current, exhibiting the role of the Kuroshio transporting dinoflagellates including HAB species. To fully understand the dynamics of dinoflagellate communities in marine ecosystems, further seasonal monitoring is foremost for correlating dinoflagellates and environmental factors while completing the reference genomic database.

Lead-up and manifestation of the Oceanic Anoxic Event 2 at the DSDP Site 398 (Vigo Seamount, NW Iberian offshore): Palynological and geochemical insights

Extreme climatic conditions, volcanism, and paleogeographical distribution presumably led to the Oceanic Anoxic Event 2 (OAE 2), one of the most disruptive events for Cretaceous ecosystems. Although the terrestrial response to this issue is barely studied, a turnover within the plant communities seems to be linked to the OAE 2, besides the well-known extinction of several marine groups. In this study, palynological and δ13Corg analyses were combined to research the sediments from DSDP Site 398 (Vigo Seamount) cores 398D-58 to 398D-56 (upper Albian to lower Turonian). The δ13Corg curve exhibits a Carbon Isotopic Excursion (CIE) observed between the interval 948,60 and 947,77 m below seafloor (mbsf), corresponding to the OAE 2. Four palynological assemblages were differentiated, ranging from the uppermost Albian to the lower Turonian. These assemblages comprised diverse marine and terrestrial communities with generally excellent preservation. In addition to previous biostratigraphic works, we present a more detailed chronostratigraphy of DSDP Hole 398D based on palynomorphs. The paleoecological reconstruction reveals the significant changes during the OAE 2 period: a decrease in the diversity and abundance of dinoflagellate cysts and a shift to angiosperm-dominated terrestrial communities (i.e., Normapolles) which, unlike other sites, occurs prior to the maximum values of δ13C.

Paleocene – Late Oligocene dinoflagellate cysts biostratigraphy, onshore Niger Delta

A new biostratigraphic biozonation for the Paleocene to Late Oligocene succession of the onshore Niger Delta has been developed based on the identification of significant stratigraphic dinoflagellate cyst events. This study is aimed at applying rarely used dinoflagellate cysts events in dating, correlating and inferring the paleoenvironment of penetrated sedimentary successions in the studied area. Palynological processing and analysis were carried out on two hundred and twenty ditch cutting samples recovered from two exploration wells (BN-1 and FJ-1) located in the Greater Ughelli and Northern Depobelts of the onshore Niger Delta respectively. Abundant and diverse dinoflagellate cysts recovered included marker Peridinales species Apectodinium sp., Palaeocystodinium australinum, and Gonyaulacales such as Areosphaeridium arcuatum, Cordosphaeridium gracile, Tuberculodinium vancampoae, Polysphaeridium zoharyi and Hystrichokolpoma rigaudiae. Three dinoflagellate cysts Palynological Zones - DPZ 100 (Early to Late Paleocene), DPZ 200 (Early to Late Eocene) and DPZ 300 (Late Eocene to Late Oligocene) are proposed herein. The biozones were subdivided into ten subzones based on the Top occurrence, Quantitative Tops and Quantitative base as well as ACME events of dinoflagellate cysts marker taxa which are used to date the rock sequence to be Paleocene to Late Oligocene. Abundant and diverse shallow outer neritic to inner neritic dinoflagellate cysts are identified from thick grey soft shales at the lower section of the studied wells. The upper section show significant reduction in dinocysts assemblage dominated by inner (coastal) neritic taxa. This dinocysts occurrence and distribution suggests inner (coastal) neritic paleoenvironment at the upper sections which deepened into shallow outer neritic conditions at the lower intervals of the studied wells. The thick brown to grey shales at the lower section and the medium to fine grained, moderately well sorted sandstone interbeds at the middle section of the studied wells are interpreted to be potential source and reservoir rocks respectively. These datasets are useful for correlating possible hydrocarbon source rocks and potential reservoir carrier beds in the Gulf of Guinea.

A review on the diversity and distribution of athecate dinoflagellates in South Atlantic and in the Atlantic sector of the Southern Ocean: Research insights and gaps.

This review summarizes the state of knowledge on athecate dinoflagellates occurring within the South Atlantic Ocean and Atlantic sector of the Southern Ocean. We compiled data from 105 articles and selected 33 addressing any aspect of athecate dinoflagellate studies. Our aim is to discuss the patterns in athecate dinoflagellate distribution by building a thorough species list and an occurrence map based on species recorded in coastal and oceanic waters. We found 69 species totaling 141 occurrences in the entire South Atlantic Ocean basin. Contradicting global trends, most species distributed throughout this region are subtropical. We linked this trend to a higher local effort in dinoflagellate research instead of higher biodiversity, especially when compared to usual hotspots in biodiversity attributed to tropical oceans. The Subantarctic and Antarctic regions had a low number of occurrences, with 12 and 5, respectively. Except for the occurrence of Gyrodinium lachryma in the Antarctic Zone, all records are unique, poorly described and never recorded again for species such as Gymnodinium baccatum and Gymnodinium antarcticum. This demonstrates that the state of knowledge regarding athecate dinoflagellates in the South Atlantic and especially in the Antarctic region is still limited due to a lack of directed investigation.

Novel Plastid Genome Characteristics in Fugacium kawagutii and the Trend of Accelerated Evolution of Plastid Proteins in Dinoflagellates.

Typical (peridinin-containing) dinoflagellates possess plastid genomes composed of small plasmids named "minicircles". Despite the ecological importance of dinoflagellate photosynthesis in corals and marine ecosystems, the structural characteristics, replication dynamics, and evolutionary forcing of dinoflagellate plastid genomes remain poorly understood. Here, we sequenced the plastid genome of the symbiodiniacean species Fugacium kawagutii and conducted comparative analyses. We identified psbT-coding minicircles, features previously not found in Symbiodiniaceae. The copy number of F. kawagutii minicircles showed a strong diel dynamics, changing between 3.89 and 34.3 copies/cell and peaking in mid-light period. We found that F. kawagutii minicircles are the shortest among all dinoflagellates examined to date. Besides, the core regions of the minicircles are highly conserved within genus in Symbiodiniaceae. Furthermore, the codon usage bias of the plastid genomes in Heterocapsaceae, Amphidiniaceae, and Prorocentraceae species are greatly influenced by selection pressure, and in Pyrocystaceae, Symbiodiniaceae, Peridiniaceae, and Ceratiaceae species are influenced by both natural selection pressure and mutation pressure, indicating a family-level distinction in codon usage evolution in dinoflagellates. Phylogenetic analysis using 12 plastid-encoded proteins and five nucleus-encoded plastid proteins revealed accelerated evolution trend of both plastid- and nucleus-encoded plastid proteins in peridinin- and fucoxanthin-dinoflagellate plastids compared to plastid proteins of nondinoflagellate algae. These findings shed new light on the structure and evolution of plastid genomes in dinoflagellates, which will facilitate further studies on the evolutionary forcing and function of the diverse dinoflagellate plastids. The accelerated evolution documented here suggests plastid-encoded sequences are potentially useful for resolving closely related dinoflagellates.

Diversity and distribution of benthic dinoflagellates in Tonga include the potentially harmful genera Gambierdiscus and Fukuyoa

Benthic dinoflagellates that can cause illness, such as ciguatera poisoning (CP), are prevalent around the Pacific but are poorly described in many locations. This study represents the first ecological assessment of benthic harmful algae species in the Kingdom of Tonga, a country where CP occurs regularly. Surveys were conducted in June 2016 in the Tongatapu island group, and in June 2017 across three island groups: Ha'apai, Vava'u, and Tongatapu. Shallow subtidal coastal habitats were investigated by measuring water quality parameters and conducting quadrat surveys. Microalgae samples were collected using either macrophyte collection or the artificial substrate method. Benthic dinoflagellates (Gambierdiscus and/or Fukuyoa, Ostreopsis, and Prorocentrum) were counted using light microscopy, followed by molecular analyses (real-time PCR in 2016 and high throughput sequencing (metabarcoding) in 2017) to identify Gambierdiscus and Fukuyoa to species level. Six species were detected from the Tongatapu island group in 2016 (G. australes, G. carpenteri, G. honu, G. pacificus, F. paulensis, and F. ruetzleri) using real-time PCR. Using the metabarcoding approach in 2017, a total of eight species (G. australes, G. carpenteri, G. honu, G. pacificus, G. cheloniae, G. lewisii, G. polynesiensis, and F. yasumotoi) were detected. Species were detected in mixed assemblages of up to six species, with G. pacificus and G. carpenteri being the most frequently observed. Ha'apai had the highest diversity with eight species detected, which identifies this area as a Gambierdiscus diversity ‘hotspot’. Vava'u and Tongatapu had three and six species found respectively. Gambierdiscus polynesiensis, a described ciguatoxin producer and proposed causative agent of CP was found only in Ha'apai and Vava'u in 2017, but not in Tongatapu in either year. Ostreopsis spp. and Prorocentrum spp. were also frequently observed, with Prorocentrum most abundant at the majority of sites. In 2016, the highest number of Gambierdiscus and/or Fukuyoa cells were observed on seagrass (Halodule uninervis) from Sopu, Tongatapu. In 2017, the highest numbers of Gambierdiscus and/or Fukuyoa from artificial substrate samples were recorded in the Halimeda dominant habitat at Neiafu Tahi, Vava'u, a low energy site. This raised the question of the effect of wave motion or currents on abundance measurements from artificial substrates. Differences in detection were noticed between macrophytes and artificial substrates, with higher numbers of species found on artificial substrates. This study provides a baseline of benthic dinoflagellate distributions and diversity for Tonga that may be used for future studies and the development of monitoring programmes.

Metabarcoding reveals marked seasonality and a distinctive winter assemblage of dinoflagellates at a coastal LTER site in the Gulf of Naples

AbstractDinoflagellates constitute an abundant and diversified component of marine plankton, mostly associated with stratified conditions typical of late spring through autumn in temperate regions. Yet, difficulties with the identification of many species limit the knowledge of their composition and seasonal succession. Here we use a 3‐year V4‐18S rDNA metabarcoding dataset (4,366,007 reads, 4650 Amplicon Sequence Variants, ASVs) collected on 48 dates at the Long‐Term Ecological Research site MareChiara (LTER–MC) to explore the diversity and temporal distribution of dinoflagellates in the Gulf of Naples (Mediterranean Sea). A large fraction of dinoflagellate ASVs (55%, 68% of the reads) were assigned to 187 species in 85 genera, while 33% (23% of the reads) were attributed to undetermined Syndiniales, and the remainder to unidentified groups. A total of 147 ASVs were assigned at 100% similarity to 135 reference sequences, corresponding to 116 species, 46 of which were putative new records for the Gulf of Naples. Cluster analysis conducted on a normalized dataset of 1199 ASVs identified four sample clusters that corresponded largely to the spring, summer, autumn and winter seasons, respectively, each including samples from all 3 years. Syndiniales were particularly abundant (43.1%) in the winter cluster, whereas Gyrodinium reached higher percentages in the summer and autumn ones (38.6% and 57.8%), Gymnodiniales sensu stricto were more abundant in spring (11.5%) and Gonyaulacales in summer (13.5%). Almost half of the ASVs analysed (561) were significantly associated with one of the four seasonal clusters (p < .05). The winter group of ASVs was particularly rich (348 ASVs) and mainly consisted of naked and parasitic taxa, which are impossible to identify in routine phytoplankton observations in light microscopy. Despite biases mainly ascribed to both the incompleteness of the reference dataset and the limited resolution of the marker gene, the metabarcoding approach has provided new insights into the ecology and distribution of this important component of the plankton, highlighting its marked seasonality along with the existence of a diversified and previously overlooked dinoflagellate community in winter.

Різноманіття та розподіл дінофлагелят у водоймах України (критико-систематична ревізія)

A critical and systematic revision of the superclass Dinoflagellata of the type Miozoa of Ukraine was performed, and the results of the generalization of retrospective and modern data on their zonal and ecological and typological distribution were given. As of 2022, 366 species (393 species and intraspecific) belonging to 3 classes, 14 orders, 45 families and 98 genera are indicated for the territorial waters of Ukraine. Over the past two decades, 108 new species have been discovered. 100 species are new to the Ukrainian sector of the Black Sea, and 8 are found for the first time in continental water bodies of Ukraine, one of which is new to science. Significant changes in the systematic composition of dinoflagellates in this period are due to both new findings and the appearance of new taxonomic combinations, which significantly expanded their generic spectrum. The most diverse orders remained: Peridiniales (118 species), which is a third of all species, Gymnodiniales (80 or 22%), and Gonyaulacales (60 or 16.4%). Among them, the most species-rich genera are Gymnodinium (41), Protoperidinium (41), Tripos (15) and Dinophysis (25) of the order Dinophysiales, the vast majority of which live in the Black Sea. A feature of the zonal distribution of dinoflagellate species on the territory of Ukraine is an increase in diversity in the southeastern direction, from the Ukrainian forest to the Black Sea. More than half of the species (54.4%) and the genera (56.6%) were noted only within one physical-geographic zone or sea. In particular, 174 (47%) species and 41 (41.8%) genera were found only in the seas. Since dinoflagellates are mainly marine algae, the greatest diversity and unique species composition is characteristic of the Black Sea, where almost 77% of all species and genera live. In desalinated Azov there were significantly less of them (21% of species and 25% of genera). In the Steppe zone of Ukraine, which has a wide range of water types, the highest diversity of dinoflagellates was observed among all terrestrial zones: 39.6% of species and 57% of genera known in Ukraine. According to ecological features, the flora of dinoflagellates was dominated by marine and breckish-marine forms (63.5%), were 2.5 times more than freshwater and breckish-reshwater forms (26.5%). A significant share was made up of species with a wide amplitude of adaptation (6.3%). Reservoirs with different degrees of myneralization, which include estuaries and myneralized reservoirs, as well as contact zones of fresh and sea waters (river mouths), had representatives of marine and brackish water complexes that are absent in other types of continental reservoirs. Estuaries ranked second after seas in terms of species richness (36.3% of species and 57% of genera) with a predominance of marine and brackish water species (58.5%). In general, 1.4 times fewer species were found in continental water bodies than in marine water areas. Lakes (22.4%) and ponds (21.6%) were in first place among continental bodies of water (with the exception of estuaries) in terms of species diversity, followed by rivers (16.4%) and swamps (15.8%), in which, of course, predominated freshwater species. There are 34 species that are widespread in Ukraine, 8 – are eurytopeans. T he composition of luminous species remained unchanged (36), and 25 are known as the causative agents of water "blooming", and 27 are toxic. Part of the species (63 or 17%) found mainly in the Black Sea are known from one reference, of which 40 species were identified more than 50 years ago, so their presence in the waters of Ukraine at the present time requires additional research. The taxonomic status of 8 species and one form has not yet been determined, so in the future the systematic composition of dinoflagellates of Ukraine will change thanks to the use of molecular phylogenetic methods.

Ostreopsis Schmidt and Coolia Meunier (Dinophyceae, Gonyaulacales) from Cook Islands and Niue (South Pacific Ocean), including description of Ostreopsis tairoto sp. nov.

It is important to decipher the diversity and distribution of benthic dinoflagellates, as there are many morphologically indistinct taxa that differ from one another in production of potent toxins. To date, the genus Ostreopsis comprises twelve described species, of which seven are potentially toxic and produce compounds presenting a threat to human and environmental health. In this study, isolates previously identified as “Ostreopsis sp. 3” were sampled from the area where it was first reported, Rarotonga, Cook Islands, and have been taxonomically and phylogenetically characterised as Ostreopsis tairoto sp. nov. Phylogenetically, the species is closely related to “Ostreopsis sp. 8”, O. mascarenensis, “O. sp. 4”, O. fattorussoi, O. rhodesiae and O. cf. siamensis. Previously, it was considered a part of the O. cf. ovata complex but can be distinguished from O. cf. ovata based on the small pores identified on this study, and from O. fattorussoi and O. rhodesiae based on relative lengths of the 2′ plates. No known palytoxin -like compounds were detected in strains investigated in this study. Strains of O. lenticularis, Coolia malayensis and C. tropicalis were also identified and described. This study advances our knowledge of biogeography, distribution, and toxins of Ostreopsis and Coolia species.

Current Information on the Diversity of Dinoflagellates of Ukraine

Presenting current information on the diversity of <i>Dinoflagellata</i> in Ukraine. The use of electron microscopy, as well as molecular genetic research methods over the past 10 years have made it possible to observe significant changes in the taxonomic system of the<i> Miozoa</i> division of the superclass <i>Dinoflagellata.</i> Based on the analysis of 216 literary sources and bringing all the names of dinoflagellates in line with those accepted in the international database AlgaeBase, it was established that the current list of <i>Dinoflagellates</i> of Ukraine includes 368 species (395 infraspecific taxa), belonging to 3 classes, 14 orders, 45 families and 98 genera. The number of species found in Ukraine is an order of magnitude lower than that currently known for<i> Miozoa</i> in the world (3636), and their distribution by order almost coincides and is very uneven: 3 orders include 63% of currently known species in the peace and 71% - in Ukraine. The most diverse orders in Ukraine are<i> Peridiniales</i> (118 species, 32%),<i> Gymnodiniales</i> (82/22%) and<i> Gonyaulacales</i> (60/16%). In comparison with the most complete review by Krakhmalnyi (2011), the species richness of dinoflagellates of Ukraine and their taxonomy underwent significant changes in the last decade. The number of species, orders and genera has increased twice and number of new species and infraspecific taxa has increased by 85 units and one species has been described as new to science. But the species diversity of some dinoflagellates regions of Ukraine remains insufficiently studied, and some of them require additional research. The analysis of the distribution of dinoflagellates in the territorial waters of Ukraine confirmed that most of them inhabit the seas (302 species and infraspecific taxa), which is more then to three times higher than in estuaries (112) and is more to twice those in aquatic complexes on the land (134). Overall, 70% were unique (not found in other ecotopes), while 30% were shared. Naturally, most of them were found in the contact zone between seas and estuaries (14/7%), 4/3% - between the estuaries and land water bodies, 3% were found in the seas and in the land water bodies, and 8/1% were found in all studied ecotopes. This shows the high role of the estuaries, as water contact zones, for the dinoflagellates diversity and the necessity for their additional studies. Among the species occurring on the land water bodies, the largest number is assigned to the Dnieper-Black Sea, Middle Dnieper and Carpathian-Danube algofloristic subprovinces, due to the presence of water contact zones of different origins and greater study of these areas.

Calcification rates of a massive and a branching coral species were unrelated to diversity of endosymbiotic dinoflagellates.

To explore the possibility that endosymbiotic dinoflagellates (Symbiodiniaceae) are associated with coral calcification rates, we investigated the diversity of symbiotic algae in coral colonies with different calcification rates within massive and branching corals (Porites australiensis and Acropora digitifera). Genotyping symbiotic algae from colonies with different calcification rates revealed that all the colonies of both species harbored mainly Cladocopium (previously clade C of Symbiodinium). The Cladocopium symbionts in P. australiensis were mainly composed of C15 and C15bn, and those in A. digitifera of C50a and C50c. We did not detect clear relationships between symbiont compositions and calcification rates within the two coral species. Our results suggest that different coral calcification rates within species may be attributed to genetic factors of coral hosts themselves and/or within symbiont genotypes.

Micronutrient content drives elementome variability amongst the Symbiodiniaceae

BackgroundElements are the basis of life on Earth, whereby organisms are essentially evolved chemical substances that dynamically interact with each other and their environment. Determining species elemental quotas (their elementome) is a key indicator for their success across environments with different resource availabilities. Elementomes remain undescribed for functionally diverse dinoflagellates within the family Symbiodiniaceae that includes coral endosymbionts. We used dry combustion and ICP-MS to assess whether Symbiodiniaceae (ten isolates spanning five genera Breviolum, Cladocopium, Durusdinium, Effrenium, Symbiodinium) maintained under long-term nutrient replete conditions have unique elementomes (six key macronutrients and nine micronutrients) that would reflect evolutionarily conserved preferential elemental acquisition. For three isolates we assessed how elevated temperature impacted their elementomes. Further, we tested whether Symbiodiniaceae conform to common stoichiometric hypotheses (e.g., the growth rate hypothesis) documented in other marine algae. This study considers whether Symbiodiniaceae isolates possess unique elementomes reflective of their natural ecologies, evolutionary histories, and resistance to environmental change.ResultsSymbiodiniaceae isolates maintained under long-term luxury uptake conditions, all exhibited highly divergent elementomes from one another, driven primarily by differential content of micronutrients. All N:P and C:P ratios were below the Redfield ratio values, whereas C:N was close to the Redfield value. Elevated temperature resulted in a more homogenised elementome across isolates. The Family-level elementome was (C19.8N2.6 P1.0S18.8K0.7Ca0.1) · 1000 (Fe55.7Mn5.6Sr2.3Zn0.8Ni0.5Se0.3Cu0.2Mo0.1V0.04) mmol Phosphorous-1 versus (C25.4N3.1P1.0S23.1K0.9Ca0.4) · 1000 (Fe66.7Mn6.3Sr7.2Zn0.8Ni0.4Se0.2Cu0.2Mo0.2V0.05) mmol Phosphorous -1 at 27.4 ± 0.4 °C and 30.7 ± 0.01 °C, respectively. Symbiodiniaceae isolates tested here conformed to some, but not all, stoichiometric principles.ConclusionsElementomes for Symbiodiniaceae diverge from those reported for other marine algae, primarily via lower C:N:P and different micronutrient expressions. Long-term maintenance of Symbiodiniaceae isolates in culture under common nutrient replete conditions suggests isolates have evolutionary conserved preferential uptake for certain elements that allows these unique elementomes to be identified. Micronutrient content (normalised to phosphorous) commonly increased in the Symbiodiniaceae isolates in response to elevated temperature, potentially indicating a common elemental signature to warming.

Reconstruction of the last cretaceous anoxic event in the Tarfaya Laayoune basin (South of Morocco): Biostratigraphy and Paleoenvironment of the Oum Debaa Formation

Abstract The Tarfaya-Laayoune coastal basin developed in a stable passive margin, where sedimentation occurred in shallow bays. During the Late Cretaceous, bituminous and phosphatic series were deposited in the shallow depression such as Sebkha Oum Debaa. In this work, the age of these Cretaceous layers are refined using a palynological approach and their paleoenvironments are described using organic geochemistry. Based on quantitative and qualitative palynological analyses, the sediments revealed a rich and diverse dinoflagellate cyst assemblage (65 taxa); among them 9 important biostratigraphic markers: Andalusiella inflata, Andalusiella ivoirensis, Andalusiella mauthei, Cerodinium diebelii, Cerodinium speciosum, Dinogymnium acuminatum, Odontochitina porifera, Trichodinium castanea, and Trithyrodinium evittii. According to the reported stratigraphic dinoflagellate taxa distribution, an age range of late Campanian to early Maastrichtian is herein proposed for the Oum Debaa Formation. This biostratigraphy update has been correlated to the Tethyan and Sub-Boreal domains. On the paleoenvironmental level, geochemical proxies have displayed an anoxic lagoon depositional which is dominated by an intermediate climate between hot / humid and arid with an often low paleoproductivity regime which induces redox conditions.

Comparative FISH mapping of 45S and 5S rDNA in the genus Gambierdiscus advances understanding of the cytogenetic diversity and mitosis of dinoflagellates

ABSTRACT Dinoflagellates are protists with exceptionally large genomes and chromosomes that lack nucleosomes. To date, information on their genome organization is scarce. Studies investigating the distribution of ribosomal RNA genes (rDNA) in plants and animals by fluorescence in situ hybridization (FISH) have provided important information to elucidate the genome organization and evolution of many species. In the present study, FISH was used to analyse the chromosomal organization of 45S and 5S rDNA and the extent of rDNA variation among five species of Gambierdiscus (G. australes, G. excentricus, G. silvae, G. carolinianus and G. caribaeus). The results, the intensity and location of the FISH signals, are summarized as follows: (1) All Gambierdiscus species have extremely high copy number of 45S rDNA repeat units arranged in a large nucleolus situated in the concave region of the typical interphasic bean-shaped nucleus. In addition, outside the large nucleolus, G. silvae and G. carolinianus have minor clusters of 45S rDNA repeats. (2) Many copies of 5S rDNA organized in one or a few clusters, depending on the species, are physically separated from the 45S rDNA but located close, peripherally, to the nucleolus. This nuclear organization is preserved during cell division. (3) Gambierdiscus australes was the species with the lowest 5S rDNA FISH signals clustered into a single site. In contrast, one major and several minor 5S rDNA clusters of FISH signals were observed in G. excentricus. We find that the species analysed can be differentiated by their species-specific FISH rDNA phenotypes demonstrating the usefulness of FISH in comparative cytogenomic studies of Gambierdiscus. In addition, using G. australes as a model, we demonstrate the usefulness of 45S and 5S rDNA as chromosomal markers to study dinomitosis, the atypical nuclear division that solely occurs in the class Dinophyceae.