Search

Dinoflagellate chromosomes are extraordinary, as their organization is independent of architectural nucleosomes unlike typical eukaryotes and shows a cholesteric liquid crystal state. 5-hydroxymethyluridine (5hmU) is present at unusually high levels and its function remains an enigma in dinoflagellates chromosomal DNA for several decades. Here, we demonstrate that 5hmU contents vary among different dinoflagellates and are generated through thymidine hydroxylation. Importantly, we identified the enzyme, which is a putative dinoflagellate TET/JBP homolog, catalyzing 5hmU production using both in vivo and in vitro biochemical assays. Based on the near-chromosomal level genome assembly of dinoflagellate Amphidinium carterae, we depicted a comprehensive 5hmU landscape and found that 5hmU loci are significantly enriched in repeat elements. Moreover, inhibition of 5hmU via dioxygenase inhibitor leads to transcriptional activation of 5hmU-marked transposable elements, implying that 5hmU appears to serve as an epigenetic mark for silencing transposon. Together, our results revealed the biogenesis, genome-wide landscape, and molecular function of dinoflagellate 5hmU, providing mechanistic insight into the function of this enigmatic DNA mark. [ABSTRACT FROM AUTHOR]

Dinoflagellates, a class of unicellular eukaryotic phytoplankton, exhibit minimal transcriptional regulation, representing a unique model for exploring gene expression. The biosynthesis, distribution, regulation, and function of mRNA N1-methyladenosine (m1A) remain controversial due to its limited presence in typical eukaryotic mRNA. This study provides a comprehensive map of m1A in dinoflagellate mRNA and shows that m1A, rather than N6-methyladenosine (m6A), is the most prevalent internal mRNA modification in various dinoflagellate species, with an asymmetric distribution along mature transcripts. In Amphidinium carterae, we identify 6549 m1A sites characterized by a non-tRNA T-loop-like sequence motif within the transcripts of 3196 genes, many of which are involved in regulating carbon and nitrogen metabolism. Enriched within 3′UTRs, dinoflagellate mRNA m1A levels negatively correlate with translation efficiency. Nitrogen depletion further decreases mRNA m1A levels. Our data suggest that distinctive patterns of m1A modification might influence the expression of metabolism-related genes through translational control. Synopsis: Unlike the scarce presence in typical eukaryotes, m1A is prevalent in dinoflagellate mRNA, m1A levels correlate with the expression of metabolism-related genes and respond to nitrogen starvation. m1A, but not m6A, is the most abundant internal mRNA modification in various dinoflagellates. With major localization in the 3'UTR, m1A in dinoflagellate mRNA negatively correlates with the translation rates of mature transcripts. m1A methylation of mRNA in dinoflagellates responds to nitrogen starvation and might regulate the translation of mRNAs related to metabolism. Unlike the scarce presence in typical eukaryotes, m1A is prevalent in dinoflagellate mRNA, m1A levels correlate with the expression of metabolism-related genes and respond to nitrogen starvation. [ABSTRACT FROM AUTHOR]

In the Baltic Sea, the dinoflagellates Apocalathium malmogiense, Biecheleria baltica, and Gymnodinium corollarium are important contributors to the spring bloom. However, their relative contribution to the bloom community cannot be unambiguously determined by conventional light microscopy due to a lack of resolution of distinctive morphological features of the three species. Here, we describe a molecular approach based on a quantitative real-time polymerase chain reaction (qPCR) primer and probe system, targeting the ITS1 and ITS2 regions of the rRNA gene for all three species and enabling their quantification. The specificity of the method was demonstrated using monocultures of A. malmogiense, B. baltica, G. corollarium as well as three other dinoflagellate species co-occurring in the Baltic Sea during spring and validated using field-collected phytoplankton samples. [ABSTRACT FROM AUTHOR]

Dinoflagellate birefringent chromosomes (BfCs) contain some of the largest known genomes, yet they lack typical nucleosomal micrococcal-nuclease protection patterns despite containing variant core histones. One BfC end interacts with extranuclear mitotic microtubules at the nuclear envelope (NE), which remains intact throughout the cell cycle. Ultrastructural studies, polarized light and fluorescence microscopy, and micrococcal nuclease-resistant profiles (MNRPs) revealed that NE-associated chromosome ends persisted post-mitosis. Histone H3K9me3 inhibition caused S-G2 delay in synchronous cells, without any effects at G1. Differential labeling and nuclear envelope swelling upon decompaction indicate an extension of the inner compartment into telosomal anchorages (TAs). Additionally, limited effects of low-concentration sirtinol on bulk BfCs, coupled with distinct mobility patterns in MNase-digested and psoralen-crosslinked nuclei observed on 2D gels, suggest that telomeric nucleosomes (TNs) are the primary histone structures. The absence of a nucleosomal ladder with cDNA probes, the presence of histone H2A and telomere-enriched H3.3 variants, along with the immuno-localization of H3 variants mainly at the NE further reinforce telomeric regions as the main nucleosomal domains. Cumulative biochemical and molecular analyses suggest that telomeric repeats constitute the major octameric MNRPs that provision chromosomal anchorage at the NE. [ABSTRACT FROM AUTHOR]

Dinophysis is an obligate mixotroph that relies on consumption of the ciliate, Mesodinium rubrum, to grow and form harmful algal blooms (HABs). In this study, blooms of Dinophysis acuminata in two NY, USA, estuaries were studied over the course of 3 yr (2019–2021) using discrete samples and an Imaging FlowCytobot (IFCB) to capture images of plankton 20–150 μm. The darkness of Dinophysis images on the IFCB was used to quantify the “fullness” or feeding state of Dinophysis cells. Culture experiments performed to ground truth this approach revealed a highly significant correlation (R = 0.98; p < 0.001) between the darkness of Dinophysis cells and the abundance of Mesodinium. With a quantitative scale developed to track the fullness of Dinophysis cells, ecosystem observations revealed the percentage of “full” Dinophysis cells increased during blooms of a large‐morphotype Mesodinium that preceded the initiation of Dinophysis blooms. A smaller morphotype Mesodinium appeared during Dinophysis bloom peaks suggesting they supported bloom maintenance. While the relative abundance of diatoms was elevated before Dinophysis blooms, other dinoflagellates and tintinnids increased in abundance during these HABs indicating they emerged within a consortium of heterotrophs and mixotrophs that may have collectively filled the same open niche as Dinophysis. This study reveals the manner in which different Mesodinium populations co‐bloom with Dinophysis to support plastid acquisition, bloom initiation, and bloom maintenance and contextualizes these changes within the larger plankton community succession associated with these HABs. [ABSTRACT FROM AUTHOR]

The planktonic dinoflagellate genus Centrodinium has been understudied, with the type species C. elongatum remaining undocumented since the original description. Here, we report C. elongatum isolated from Mazatlán, Mexican Pacific. In the chains, the posterior daughter cell with an incomplete apical horn shows the morphology of C. elongatum, while the anterior daughter cell with complete epitheca corresponds to C. pulchrum. For the first time, a species of Centrodinium sensu stricto (highly laterally flattened species with horns) was cultured. An unarmored life stage, known as Murrayella ovalis, derived from the spheroplast after ecdysis. In the rDNA molecular phylogenies, C. elongatum (=C. pulchrum) nested as basal to morphologically similar species (C. eminens and C. intermedium) and as a sister group of a former Murrayella species, C. punctatum. C. elongatum differs from C. eminens and C. intermedium in the chain formation, second apical (2′) plate not being divided, horns with coarse poroid ornamentation, and missing prominent distal spinules. The taxonomy of Centrodinium sensu stricto is revised, with a discussion in the identities of C. complanatum, C. eminens, and C. maximum. The name C. deflexum is restored as a senior synonym of C. intermedium and C. ovale. [ABSTRACT FROM AUTHOR]

Dinoflagellates are a remarkable group of protists, not only for their association with harmful algal blooms and coral reefs but also for their numerous characteristics deviating from the rules of eukaryotic biology. Genome research on dinoflagellates has lagged due to their immense genome sizes in most species (~ 1-250 Gbp). Nevertheless, the last decade marked a fruitful era of dinoflagellate genomics, with 27 genomes sequenced and many insights attained. This review aims to synthesize information from these genomes, along with other omic data, to reflect on where we are now in understanding dinoflagellates and where we are heading in the future. The most notable insights from the decade-long genomics work include: (1) dinoflagellate genomes have been expanded in multiple times independently, probably by a combination of rampant retroposition, accumulation of repetitive DNA, and genome duplication; (2) Symbiodiniacean genomes are highly divergent, but share about 3,445 core unigenes concentrated in 219 KEGG pathways; (3) Most dinoflagellate genes are encoded unidirectionally and are not intron-poor; (4) The dinoflagellate nucleus has undergone extreme evolutionary changes, including complete or nearly complete loss of nucleosome and histone H1, and acquisition of dinoflagellate viral nuclear protein (DVNP); (5) Major basic nuclear protein (MBNP), histone-like protein (HLP), and bacterial HU-like protein (HCc) belong to the same protein family, and MBNP can be the unifying name; (6) Dinoflagellate gene expression is regulated by poorly understood mechanisms, but microRNA and other epigenetic mechanisms are likely important; (7) Over 50% of dinoflagellate genes are "dark" and their functions remain to be deciphered using functional genetics; (8) Initial insights into the genomic basis of parasitism and mutualism have emerged. The review then highlights functionally unique and interesting genes. Future research needs to obtain a finished genome, tackle large genomes, characterize the unknown genes, and develop a quantitative molecular ecological model for addressing ecological questions. [ABSTRACT FROM AUTHOR]

Hatcheries nationwide suffer from unexplained acute production failures, termed crashes. The microbiota of oysters relates to larval health with previous studies showing that some bacterial species have positive and others negative effects on oyster health. To investigate microbial correlates of crashes, we collected samples from every batch of oyster larvae (Crassostrea virginica) produced by the Horn Point Laboratory Oyster Hatchery since 2021 and analyzed the microbiota of 15 of those batches over their duration in the hatchery, from age of 3 to 5 days until either harvest or complete die off of the batch. Across events, die-offs generally became evident at or after six days of age. We found that the microbiota of oyster larvae appears to respond to die-off events with crashed batches having fundamentally different microbiota than good batches at age 7 to 9 and 9 to 12 days. Crashed batches were often taken over by microeukaryotes and bacterial taxa from the Protobacteria and Bacteroidetes phyla. However, this presumably opportunistic community differed between batches. Observed Vibrio species level groups did not appear to be oyster pathogens and appeared to respond to, rather than precede, crashes. The microbiota of 3 to 5 day old larvae were statistically related to whether a die-off occurred later in the larval batches' life, only when the taxa were first agglomerated to family level. The detection of two microbial species not previously known to associate with oysters, along with an increased presence of Dinophyceae, predominantly the toxin-producing Gyrodinium jinhaense, in 3 to 5 day old oyster larvae was statistically linked with subsequent batch crashes. This study suggests that the health of larval oysters shapes their microbiome. Conversely, it provides hints that the microbiome of larvae, and perhaps harmful algae, may drive hatchery crashes. [ABSTRACT FROM AUTHOR]

Cryptophytes are abundant and ubiquitous microalgae that constitute a major plastid source for kleptoplastidic ciliates and dinoflagellates. Despite their ecological significance, the understanding of their light preferences and photophysiology remains limited. Here, we provide a comprehensive study of the response of the haploid strain Teleaulax amphioxeia (Cr10EHU) to varying light irradiance. This strain is capable of growing under a wide range of irradiance levels, notably by finely tuning the different pigments bound to the membrane light‐harvesting proteins. Analysis of the luminal phycoerythrin content revealed remarkable flexibility, with phycoerythrin emerging as a pivotal protein facilitating acclimation to varying light levels. Detailed ultrastructure examinations unveiled that this adaptability was supported by the synthesis of large thylakoidal vesicles, likely enhancing the capture of green photons efficiently under low light, a phenomenon previously undocumented. Teleaulax amphioxeia Cr10EHU effectively regulated light utilization by using a cryptophyte state transition‐like process, with a larger amplitude observed under high growth irradiance. Furthermore, our results revealed the establishment of growth irradiance‐dependent non‐photochemical quenching of fluorescence, likely inducing the dissipation of excess light. This study underscores the particularities and the significant photoadaptability of the plastid of the haploid form of T. amphioxeia. It constitutes a comprehensive photophysiological characterization of the Cr10EHU strain that paves the way for future studies of the kleptoplastidy process. [ABSTRACT FROM AUTHOR]

A two-years study (March 2021 to February 2023) was carried out at the Kanewal Community Reservoir, an important water storage reservoir in central Gujarat, to assess the diversity and seasonal variation of the planktonic community. During the study period, a total of 60 phytoplankton species were recorded, belonging to 9 classes, 25 orders and 39 families. Class-wise percentage composition of phytoplankton showed a diverse array during the study period. The species gradient of phytoplankton was as follows: Bacillariophyceae (20) > Zygnematophyceae (14) > Cyanophyceae (10) > Chlorophyceae (9) > Euglenophyceae (2) > Trebouxiophyceae (2) > Dinophyceae (1) > Klebsormidiophyceae (1) > Ulvophyceae (1). Thirty (30) different zooplankton species were recorded during this study, belonging to 11 classes, 14 orders and 19 families. The number of abundant species remained constant throughout the study period. The recorded number of common zooplanktonic species also remained steady (14). However, the number of rare species slightly increased to two (2), which indicates a slight increase in the occurrence of less prevalent species. The highest density of zooplankton was observed during the summer, and the lowest in the monsoon season. Overall, it was found that KCR (Kanewal Community Reservoir) contains a higher number of phytoplankton species (60) compared to zooplankton (30), which could be a consequence of the voluminous hydrological regime with abundant occurrence of macrophyte elements. [ABSTRACT FROM AUTHOR]

Human‐induced dissolved organic nitrogen (DON) input is impacting coastal ecosystems globally, and the shift from diatoms to dinoflagellates may be associated with increasing DON concentrations and changing DON compositions. Based on field microcosm experiments, changes in three‐dimensional fluorescence component and extracellular leucine aminopeptidase activity were used to reveal the effects of DON on diatom and dinoflagellate growth. Additionally, a Nutrients–bi‐Phytoplankton–Detritus biogeochemical model was employed to elucidate the kinetic mechanism of DON on the shift from diatoms to dinoflagellates in the Bohai Sea (BS). Our results revealed that shifting diatom–dinoflagellate dominance was associated with the hydrophobic component of terrestrial DON. Dinoflagellates (i.e., Karenia mikimotoi) efficiently assimilated humic‐like substances in hydrophobic DON; whereas, diatoms (i.e., Chaetoceros spp.) efficiently utilized the protein‐like components in hydrophilic DON. The reason for this was the higher extracellular leucine aminopeptidase activity of dinoflagellates compared to that of diatoms, which enabled them to degrade humic‐like substances and protein‐like components more effectively. The modeling study clarified that the DON composition, particularly the proportion of hydrophobic DON, regulated the shift from diatoms to dinoflagellates. Our study provides insight into the mechanisms underlying phytoplankton regime shifts in the BS and valuable guidance for decreasing eutrophication by controlling terrestrial DON inputs and compositions. Plain Language Summary: Human‐induced nitrogen input is causing major changes in coastal ecosystems worldwide and posing a threat to human well‐being. In the Bohai Sea (BS), the increase in DON concentrations and changes in its composition have been linked to harmful algal blooms and a shift from diatom to dinoflagellate dominance. This study investigated the mechanism behind the shift from diatoms to dinoflagellates using field experiments, a biogeochemical model, and techniques for analyzing organic chemicals. Our findings indicated that dinoflagellates (represented by Karenia mikimotoi) can efficiently assimilate humic‐like substances in hydrophobic DON, and that diatoms (represented by Chaetoceros spp.) can effectively utilize protein‐like components in hydrophilic DON. This difference arose because of higher extracellular leucine aminopeptidase activity in dinoflagellates compared to diatoms, enabling them to degrade humic‐like substances and protein‐like components more effectively. Our modeling study further revealed that the DON composition, particularly the proportion of hydrophobic DON, regulated the shift from diatoms to dinoflagellates. These insights into the mechanisms driving phytoplankton regime shifts in the BS provide valuable guidance for mitigating eutrophication by controlling terrestrial DON inputs and compositions. Key Points: Karenia mikimotoi can efficiently assimilate humic‐like substancesChaetoceros spp. can efficiently utilize protein‐like componentsKarenia mikimotoi has higher extracellular leucine aminopeptidase activity than Chaetoceros spp. [ABSTRACT FROM AUTHOR]

Harmful Algal Blooms (HABs) can produce phycotoxins that accumulate in shellfish and subsequently poison aquatic predators and human consumers, potentially causing significant economic impacts to the shellfish aquaculture industry. HAB events are challenging to foresee as they are driven by complex inter‐annual and seasonal changes in physical, chemical and biological factors. Accounting for these environmental drivers and their interactions in statistical models allows for the development of HAB early warning systems. Typically, these have a forecasting horizon of 1–2 weeks, allowing shellfish businesses and regulators to increase monitoring intensity and take evasive action, including harvesting suspensions to protect consumer health. However, there is critical need for longer‐term predictions of risk, to enable more proactive mitigation, business planning, harvest scheduling and supply chain management. We present a statistical framework for providing seasonal‐scale early warnings of the occurrence and impacts of Dinophysis spp. HABs on shellfish aquaculture in Scotland, UK. We use penalized smooth functions of winter‐spring daily sea surface temperature to predict the severity and impact of ensuing summer blooms, including the percentage of toxicity measurements exceeding the harvesting closure threshold, as well as the anticipated start, end, and overall duration of closures. We illustrate the application of this framework to two Scottish aquaculture regions: One with a high spatial concentration of harvesting sites (Shetland) and one with more dispersed sites (West Scotland and the Hebrides). Through a comprehensive yearly prediction experiment, we demonstrate considerable skill in predicting the impact of unseen HAB seasons at a regional level. Key Points: We present a new statistical approach for seasonal predictions of toxic Dinophysis species blooms in two regions of ScotlandResults indicate a link between low winter‐spring sea surface temperatures and high summer toxin concentrations in shellfish samplesWe demonstrate improved early warnings of harmful summer blooms using the first 120 days of sea surface temperature measurements each year [ABSTRACT FROM AUTHOR]

Some marine microalgae and cyanobacteria form mutualistic symbioses with diverse invertebrates, particularly cni-darians. Among microalgae, dinoflagellates in the family Symbiodiniaceae are the most well-known symbiotic partners of jellyfish and corals. However, the symbioses involving other dinoflagellate families, nano- and micro-flagellates, diatoms, and cyanobacteria with cnidarians are not well understood. As an initial step, it is essential to explore the survival of these microorganisms inside cnidarians. We monitored the survival of eight microalgal species (nine strains) and one cyanobacterium species every day for seven days after injecting each into the medusa of the moon jellyfish Aurelia au-rita. The dinoflagellates Effrenium voratum (free-living [FL] and living-in-coral strains), Cladocopium infistulum, Pro-rocentrum cordatum, Prorocentrum koreanum, Symbiodinium microadriaticum, the prasinophyte Tetraselmis suecica, the chlorophyte Dunaliella salina, and the raphidophyte Heterosigma akashiwo survived inside the medusa, while the cyanobacterium Synechococcus sp. was not detected. Additionally, E. voratum (FL) survived within the medusa for 60 days and gradually spread to adjacent areas, indicating potential for artificially established symbiosis. The results of this study provide a basis for artificial symbiosis between microalgae and invertebrates. [ABSTRACT FROM AUTHOR]

The dinoflagellate genus Bysmatrum is an unusual member of the Peridiniales and cannot be attributed to any known family. Bysmatrum differs from typical peridinialean genera in that the second and third anterior intercalary plates are separated and both antapical plates are asymmetrical. Currently, Bysmatrum encompasses six epibenthic or tide-pool species, but information on their genetic diversity and biogeography remains limited. In the present study, we obtained five strains of Bysmatrum from the South China Sea by isolating single cells and three strains from Ingril, a French Mediterranean lagoon by incubating sediments. Strains from Ingril Lagoon displayed the plate formula Po, cp, X, 4′, 3a, 7′′, 6C, 4S, 5′′′, 2′′′′. They also exhibited an elongated nucleus in the hypocone and a type B eyespot. Smooth and spherical cysts were produced in culture. Small and/or partially large subunit ribosomal DNA sequences were obtained for all eight strains. Molecular phylogeny was inferred using these concatenated sequences through maximum likelihood and Bayesian inference methods. Bysmatrum granulosum and B. subsalsum were identified from Thailand and China for the first time, each of them comprising of two ribotypes. Bysmatrum ingrilense sp. nov. was monophyletic and closest to B. subsalsum ribotype B. Pinnatoxin and related toxins were examined in two strains of Bysmatrum ingrilense by LC-MS/MS, but none were detected. Our results highlight that the diversity of Bysmatrum might be underestimated. [ABSTRACT FROM AUTHOR]

Our study focused on the effects of various physical and chemical parameters, along with certain heavy metals, on the spatiotemporal distribution of phytoplankton in Lake Oubeira from January 2021 to January 2022. Monthly sampling of phytoplankton, along with measurements of specific physicochemical parameters and heavy metals, was conducted at two stations characterized by distinct physico-chemical properties. All data analyses in this study were performed using R, version 4.0.1 (R Core Team 2020). The observations of the morphological and anatomical characteristics of phytoplankton collected from Lake Oubeira allowed us to identify 48 genera belonging to five classes: Cyanophyceae, Bacillariophyceae, Chlorophyceae, Euglenophyceae, and Dinophyceae. Notably, there was a dominance of cyanophytes, with 9 toxic genera identified. The measured levels of heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) in Lake Oubeira's waters revealed significant spatiotemporal variation. The highest concentrations of these heavy metals were recorded during the summer, while the lowest values were observed in autumn. An in-depth principal component analysis (PCA) considering both "station" and "season" factors indicated a spatiotemporal variation between several parameters, including pH, dissolved oxygen (O2), Pb, Cd, and the density of certain phytoplankton taxa (Euglenophyceae, Dinophyceae, Bacillariophyceae, and Chlorophyceae). Our findings show that during summer, the waters of Lake Oubeira are warm, alkaline, and less oxygenated, with a high abundance of Euglenophyceae taxa. In contrast, spring conditions are characterized by cooler, well-oxygenated waters with a richness of Dinophyceae, Bacillariophyceae, and Chlorophyceae taxa. During winter, the waters are cold, less alkaline, and less oxygenated. [ABSTRACT FROM AUTHOR]

Harmful algal bloom events occur in salt, brackish, and fresh water. In bodies of water such as oceans and estuaries, diatoms or dinoflagellates form "tides" that produce toxins associated with seafood poisoning, including paralytic shellfish poisoning, or respiratory distress from inhalation of aerosolized toxins. Cyanobacteria predominantly bloom in fresh water; they can produce microcystins; cylindrospermopsin; and other toxins that humans or animals might be exposed to through water contact, inhalation, or ingestion. Animals that become ill or die can be sentinels for harmful algal bloom events. In a One Health approach, information about harmful algal bloom exposures and health effects support efforts to detect these events and mitigate and prevent associated illnesses. Human, animal, and environmental health partners can work together to document the occurrence and impacts of harmful algal bloom events and characterize associated illnesses. [ABSTRACT FROM AUTHOR]

• First record of the presence of P. gatunense in South Africa. • Reappearance of P. bipes , last reported from South Africa during the 1930s. • Both are potential bloom-forming associated with several problems. • The morphology, taxonomy geographical distribution and limited ecology are discussed. The common freshwater dinoflagellate genus Peridinium includes the species P. gatunense and P. bipes , which are found globally. Despite forming a significant portion of algal communities, research on dinoflagellates in Africa is limited. This paper reports the first record of the presence of P. gatunense in South Africa, as well as the reappearance of P. bipes , which was last reported from South Africa during the 1930s. Light and scanning electron microscopy were used for species identification. Knowledge about the presence of these species is crucial because both are potential bloom-forming and associated with several problems having ecological impacts. The presence of both these species has potential in inhibiting the growth of the problematic cyanobacterium Microcystis aeruginosa , as demonstrated by previous studies. It may present a natural and effective solution for the remediation of water bodies subjected to harmful cyanobacterial blooms. These insights are crucial for proactive management of freshwater ecosystems in the country. This paper discusses the morphology, taxonomy, geographical distribution, and some ecological aspects of P. gatunense and P. bipes. [ABSTRACT FROM AUTHOR]

Decapod crustaceans and their associated fisheries are an important resource globally, and demand for seafood continues to grow alongside a growing human population. With a combined 2023 value of €36 million in Ireland, three species of brachyuran crabs, the velvet crab (Necora puber Linnaeus, 1767), edible crab (Cancer pagurus Linnaeus, 1758), spider crab (Maja squinado Herbst, 1788)), and the European lobster (Homarus gammarus Linnaeus, 1758) are decapods of commercial importance. These species are also important components of their respective ecosystems. Parasite infection can affect the health of crustaceans and may affect population productivity. Microparasites, including paramyxids (Hematodinium spp.) and microsporidians can infect decapod crustaceans and have a range of effects on their hosts. We assessed three microparasites in four crustacean species. Paramarteilia canceri was found in all three crab species, and we provide the first genetic confirmation in spider crabs. A microsporidian associated with cotton crab disease, Ameson sp. was identified in N. puber , along with a second species of microsporidian which will require further classification. None of the three parasite groups were identified in Homarus gammarus. Species of Hematodinium were not identified in any of the species studies. Our work highlights the need for parasite surveys to uncover parasite diversity and prevalence in crustaceans to help elucidate host-parasite interactions, and the potential impacts of parasites. [ABSTRACT FROM AUTHOR]

ENSO phases produce changes in precipitation and river flow in Eastern South America. We aimed to evaluate phytoplankton and surface sediment diatoms' response to ENSO within the Río de la Plata estuary. A 180-km-long transect off the Uruguayan coast was undertaken in May 2009 (La Niña) and May 2010 (El Niño), where physical, chemical and biological variables were measured. During El Niño we registered lower temperatures/salinities throughout the transect, and the riverine zone was specifically more homogeneous in terms of temperature, salinity, turbidity and chlorophyll-a than during La Niña. We observed changes in the species composition of both planktonic and sediment diatoms. Concomitantly, a significant depletion in planktonic diatom abundance and richness in both planktonic and benthic domain during El Niño was observed. In addition, there was a higher proportion of dinoflagellates than during La Niña, which was explained by a higher water column stability. The dominance of the chain-forming and meso-eutrophic diatom Aulacoseira was registered during El Niño in both domains, mainly in the fluvial zone, related to a high river discharge. Our findings are important to anticipate changes in microalgae composition related to oceanographic variability during potential ENSO events. [ABSTRACT FROM AUTHOR]

Species composition, distribution density and biomass of phytoplankton were surveyed in the coastal area of eastern Aniva Bay in May-October 2018. In total, 297 species and intraspecific taxa of microalgae belonged to Bacillariophyta, Chlorophyta, Cryptophyta, Dinophyta, Euglenophyta, Crysophyta were found. Their total abundance ranged from 14.8 . 103 to 1024.7 . 103 cells/L, biomass was 19.4–324.6 mg/m3. Two peaks in the abundance (in June and October) and five peaks in the biomass (in May, June, September and October) were noted. The bulk of population was formed by diatoms in spring and autumn, and flagellates in summer. A bloom of potentially toxic diatoms of genus Pseudo-nitzschia was registered. In this connection, monitoring of toxic species is necessary for planning and development of aquaculture farms.

A cruise was conducted in the summer of 2023 from the Pearl River Estuary (PRE) to the adjacent waters of the Xisha Islands in the northern South China Sea (NSCS) to investigate the distribution, community structure, and assembly patterns of eukaryotic and prokaryotic phytoplankton using high-throughput sequencing (HTS) and microscopic observation. Dinophyta were the most abundant phylum in the eukaryotic phytoplankton community based on HTS, accounting for 92.17% of the total amplicon sequence variants (ASVs). Syndiniales was the most abundant order among eukaryotic phytoplankton, whereas Prochlorococcus was the most abundant genus within cyanobacteria. The alpha diversity showed the lowest values in the PRE area and decreased gradually with depth, while cyanobacteria exhibited higher alpha diversity indices in the PRE and at depths ranging from 75 m to 750 m. The morphological results were different from the data based on HTS. Diatoms (37 species) dominated the phytoplankton community, with an average abundance of 3.01 × 104 cells L-1, but only six species of dinoflagellate were observed. Spearman correlation analysis and redundancy analysis (RDA) showed that the distribution and community structure of phytoplankton were largely influenced by geographical location and environmental parameters in the NSCS. The neutral community model (NCM) and null model indicated that deterministic processes played a significant role in the assembly of eukaryotic phytoplankton, with heterogeneous selection and homogeneous selection accounting for 47.27 and 29.95%, respectively. However, stochastic processes (over 60%) dominated the assembly of cyanobacteria and undominated processes accounted for 63.44%. In summary, the formation of eukaryotic phytoplankton was mainly influenced by environmental factors and geographic location, but the assembly of cyanobacteria was shaped by both stochastic processes, which accounted for over 60%, and environmental selection in the NSCS. [ABSTRACT FROM AUTHOR]

Phytoplankton blooms have become a global concern due to their negative impacts on public health, aquaculture, tourism, and the economic stability of coastal regions. Therefore, elucidating the shifts in phytoplankton community structure and abundance, as well as their environmental drivers, is crucial. However, existing studies often fail to capture the detailed dynamics of phytoplankton blooms and their environmental triggers due to low temporal observation resolution. In this study, high temporal resolution (daily) samples were collected over 43 days to investigate the influence of environmental factors on phytoplankton in Qinhuangdao in the summer. During the observation period, a total of 45 phytoplankton species were identified, comprising 26 Bacillariophyta species, 16 Dinophyta species, 2 Euglenophyta species, and 1 Chromophyta species. Interestingly, a lag bloom pattern of phytoplankton behind freshwater input was observed across day-to-day samples. Phytoplankton blooms typically lagged 1-3 days behind periods of decreased salinity and nutrient input, suggesting that freshwater influx provides the foundational materials and benefits for these blooms. Moreover, the phytoplankton blooms were triggered by six dominant species, i.e., Chaetoceros spp., Pseudo-nitzschia delicatissima, Skeletonema costatum, Protoperdinium spp., Leptocylindrus minimus, Pseudonitzschia pungens, and Thalassiosira spp. Consequently, the succession of phytoplankton showed a predominant genera shift in the following sequence: Nitzschia, Protoperdinium, and Prorocentrum - Skeletonema - Pseudonitzschia - Gymnodinium - Leptocylindrus. Besides that, a deterministic process dominated phytoplankton community assembly across time series, and DIP is a key factor in shifting the phytoplankton community structures in this area. In summary, our study offers high-resolution observations on the succession of phytoplankton communities and sheds light on the complex and differentiated responses of phytoplankton to environmental factors. These findings enhance our understanding of the dynamics of phytoplankton blooms and their environmental drivers, which is essential for the effective management and mitigation of their adverse impacts. [ABSTRACT FROM AUTHOR]

Simple Summary: This review highlights the intricate interactions between two major constituents of marine ecosystems: dinoflagellates and heterotrophic bacteria. Dinoflagellates typically associate with a diverse array of heterotrophic bacteria, which are not limited to but predominantly consist of phyla such as Alphaproteobacteria, Gammaproteobacteria, and the Cytophaga–Flavobacterium–Bacteroides group. These bacterial communities engage with dinoflagellates in a multifaceted manner, including nutrient exchange, the secretion of pathogenic substances, and involvement in the synthesis of chemical entities. Crucially, the process of horizontal gene transfer from bacteria is a significant force sculpting the genomic architecture of dinoflagellates. The objective of this review is to shed light on the dynamic interactions between dinoflagellates and their bacterial partners, examining the relationship through a physiological, ecological, and evolutionary perspective. Dinoflagellates and heterotrophic bacteria are two major micro-organism groups within marine ecosystems. Their coexistence has led to a co-evolutionary relationship characterized by intricate interactions that not only alter their individual behaviors but also exert a significant influence on the broader biogeochemical cycles. Our review commenced with an analysis of bacterial populations, both free-living and adherent to dinoflagellate surfaces. Members of Alphaproteobacteria, Gammaproteobacteria, and the Cytophaga–Flavobacterium–Bacteroides group are repeatedly found to be associated with dinoflagellates, with representation by relatively few genera, such as Methylophaga, Marinobacter, and Alteromonas. These bacterial taxa engage with dinoflagellates in a limited capacity, involving nutrient exchange, the secretion of pathogenic substances, or participation in chemical production. Furthermore, the genomic evolution of dinoflagellates has been profoundly impacted by the horizontal gene transfer from bacteria. The integration of bacterial genes into dinoflagellates has been instrumental in defining their biological characteristics and nutritional strategies. This review aims to elucidate the nuanced interactions between dinoflagellates and their associated bacteria, offering a detailed perspective on their complex relationship. [ABSTRACT FROM AUTHOR]

Protoperidinium claudicans is a planktonic, heterotrophic, bioluminescent dinoflagellate species commonly found in neritic waters. It has long been considered to display phenotypic variation in its second anterior intercalary plate, which could vary between quadra, penta and hexa. The equivalent spinose, cordate cyst goes under the name of Votadinium spinosum. Here we perform incubation experiments with cysts from France, Canada, China and Japan, which demonstrate that P. claudicans forms a species complex, with at least two ribotypes with a penta configuration (P. claudicans) and one with a quadra configuration (P. carriae sp. nov.). A fossil-based cyst, V. multispinosum sp. nov., is described as the equivalent of P. carriae. Molecular phylogenetics using large subunit ribosomal DNA supports these observations. The cyst–theca relationships for Votadinium psilodora and another, undescribed, cordate, spineless Votadinium species are also reported from China. Macromolecular analyses of the cyst wall of V. multispinosum reveal it is comprised of a protein-rich carbohydrate compound. We show that this compound is not uncommon in dinoflagellate and ciliate cysts and that it is unlikely to preserve very well upon sedimentation and burial. [ABSTRACT FROM AUTHOR]

In the northeastern part of the Black Sea, dinoflagellate species new for this area have been recorded: Oxyhysis oxytoxoides, Spatulodinium pseudonoctiluca, Scaphodinium mirabile, and Actiniscus pentasterias. These species, previously indicated only for the waters of Bulgaria, Romania, Turkey, Georgia, Ukraine, and Crimea, have been found in the pelagic zone of the northeastern part of the Black Sea over the past two decades: in the area from Abkhazia to the Kerch Strait. [ABSTRACT FROM AUTHOR]

The Amazon River plume (ARP) has been shown to support high rates of nitrogen fixation and primary production. However, nitrogen fixation alone cannot account for total primary production determined in the region, hinting that other nitrogen uptake processes might play a role. For the first time, we measured nitrate uptake rates in the ARP during three cruises in May 2018, June 2019 and April/May 2021, along with primary production rates and an analysis of phytoplankton community composition via high performance liquid chromatography. Based on a classification according to the salt content the region was divided into estuarine (ES), mesohaline (MH) and oceanic (OC) stations. Primary production was light limited near the river mouth at ES stations and was maximal off the coasts of French Guiana and Suriname, where also nitrate uptake was highest with rates of 11.4 mmol m−2 d−1. The role of eddies pinching off a deflecting plume are discussed as possible reason for higher nutrient concentrations at the MH stations. Surprisingly, at most MH stations north of 5°N, nitrate uptake rates were low despite the presence of sufficient substrate concentration (up to 1.44 μM nitrate). Diatoms, dinoflagellates or Synechococcus sp. dominated phytoplankton communities. OC stations showed lowest productivity rates in accordance with oligotrophic conditions. However, rates seem to be sufficient to completely deplete the remaining riverine nitrate, preventing its export to the open ocean. Plain Language Summary: The Amazon River is thought to deliver important nutrients to the Western Tropical North Atlantic, which enable high phytoplankton growth and especially favor nitrogen fixers. Previous studies have focused on nitrogen fixation, but we propose that other nitrogen sources could also be important in the river plume to support the high phytoplankton growth there. In this study, we measured the uptake of nitrate by phytoplankton in the plume for the first time. We found that nitrate uptake is of variable importance for phytoplankton growth in the Amazon River plume; it seems to be more important close to the river mouth, where diatoms and dinoflagellates dominate, compared to the northern plume, where nitrogen fixers are dominant. Investigations like this will help us to better understand, which nitrogen sources are important for the growth of different phytoplankton species in the plume. With this information, we can improve predictions of competition of phytoplankton species for nitrogen and their general growth in the future. Some phytoplankton groups have a higher potential to contribute to oceanic CO2 storage than others, so understanding the future of these phytoplankton groups is critical to any assessment of the amount of CO2 that can be stored by the ocean. Key Points: Nitrate uptake rates were measured in the Amazon River plume for the first time to resolve its role for overall productivity in the plumeNitrate uptake displayed a pronounced gradient and was not only regulated by concentrationsNitrate from the Amazon River is completely consumed on the shelf and not exported to the open ocean [ABSTRACT FROM AUTHOR]

The recognition and use of algae in the very trend-driven cosmetic industry is progressively increasing. Up to now, the main focus was on large seaweeds and a limited number of microalgae. However, motile microalgae, flagellates, remain underscored in this aspect, although some of them are utilized commercially. Flagellates from different taxonomic groups occupy various habitats and contain bioactive high-value multifunctional compounds, some of which are novel. Moreover, they may simultaneously produce different substances, which together with the development of downstream processing technologies, makes them a promising source for modern biotechnology. The present review covers data on 411 strains, 251 species from 110 genera from 6 phyla, and is oriented generally towards less explored flagellates. It demonstrates their great potential as bearers of interesting novel compounds that can be beneficially applied in modern cosmetics. Safety aspects of both sources and products are also discussed. Considering the gaps in the knowledge, the necessity to expand the research on both well-known and yet unexplored microalgae is shown, encouraging the development of upstreaming processes, including phycoprospecting. Last but not least, this paper outlines the role of living culture collections and of using good taxonomic expertise before running the biochemical tests, cultivation, and bioengineering experiments. [ABSTRACT FROM AUTHOR]

Dinoflagellates are an abundant and diverse group of protists representing a wealth of unique biology and ecology. While many dinoflagellates are photosynthetic or mixotrophic, many taxa are heterotrophs, often with complex feeding strategies. Compared to their photosynthetic counterparts, heterotrophic dinoflagellates remain understudied, as they are difficult to culture. One exception, a long‐cultured isolate originally classified as Amphidinium but recently reclassified as Oxytoxum, has been the subject of a number of feeding, growth, and chemosensory studies. This lineage was recently determined to be closely related to Prorocentrum using phylogenetics of ribosomal RNA gene sequences, but the exact nature of this relationship remains unresolved. Using transcriptomes sequenced from culture and three single cells from the environment, we produce a robust phylogeny of 242 genes, revealing Oxytoxum is likely sister to the Prorocentrum clade, rather than nested within it. Molecular investigations uncover evidence of a reduced, nonphotosynthetic plastid and proteorhodopsin, a photoactive proton pump acquired horizontally from bacteria. We describe the ultrastructure of O. lohmannii, including densely packed trichocysts, and a new type of mucocyst. We observe that O. lohmannii feeds preferentially on cryptophytes using myzocytosis, but can also feed on various phytoflagellates using conventional phagocytosis. O. lohmannii is amenable to culture, providing an opportunity to better study heterotrophic dinoflagellate biology and feeding ecology. [ABSTRACT FROM AUTHOR]

SUMMARY: Dinoflagellates have a rich history of characterization of their membrane‐reinforcing sterols because of a structural diversity and chemotaxonomic utility uncommon to other classes of algae. The Kareniaceae are no exception in that they produce sterols, often containing a Δ8(14) nuclear unsaturation, which are rare in most other dinoflagellate groups. A continuing goal of our laboratory is to examine the sterols of previously uncharacterized dinoflagellates to assess their sterol‐based chemotaxonomy compared to other members of the Dinophyceae. Asterodinium gracile, a member of the Kareniaceae, has not been commercially available for study until recently. To this end, our objective was to characterize the sterols of A. gracile to determine whether they match the 4α‐methyl‐substituted, Δ8(14)‐nuclear‐unsaturated sterols, such as (24R)‐4α‐methyl‐5α‐ergosta‐8(14),22‐dien‐3β‐ol (gymnodinosterol; C29:2) and 27‐nor‐(24R)‐4α‐methyl‐5α‐ergosta‐8(14),22‐dien‐3β‐ol (brevesterol; C28:2), of most species within the canonical genera Karenia, Karlodinium and Takayama, or instead the 4‐desmethyl sterols, such as 27‐nor‐(24R)‐23‐methyl‐ergosta‐8(14),22‐dien‐3β‐ol (C28:2), of its chemotaxonomically atypical, yet closest phylogenetic relative, Karenia papilionacea. We have observed A. gracile to produce two 4α‐methyl‐substituted sterols with the suggested structures of 4α‐methyl‐5α‐ergosta‐8(14)‐en‐3β‐ol (C29:1) and 4α‐methyl‐5α‐ergosta‐8(14),24(28)‐dien‐3β‐ol (amphisterol, C29:2), as major sterols amongst five other minor sterols, which included the common dinoflagellate sterol cholest‐5‐en‐3β‐ol (cholesterol, C27:1), but did not include gymnodinosterol or brevesterol (as in most canonical Kareniaceae) or 27‐nor‐(24R)‐23‐methyl‐ergosta‐8(14),22‐dien‐3β‐ol (as found in K. papilionacea). Detection of amphisterol and 4α‐methyl‐5α‐ergosta‐8(14)‐en‐3β‐ol is notable because they are sterols associated with some species of Amphidinium, such as Amphidinium carterae, and, to our knowledge, have not been observed in a member of the Kareniaceae before. Discovery of these major sterols in A. gracile expands our knowledge of the range of sterols produced by the Kareniaceae and indicates a shared chemotaxonomy with some species of Amphidinium. [ABSTRACT FROM AUTHOR]

The Haruku Strait in the Central Moluccas is a potential marine resource located eastern Indonesia. Small pelagic fishes have been noted in abundance in the waters of this strait. Their abundance is mainly associated with the ample amount of plankton organisms serving as food for the former. To address the abundance of phytoplankton in Haruhu Strait, a study was carried out in September 2022. Sampling was achieved using a sample bottle from a depth of 1 meter. After that, the sample was filtered with a Kitahara net. Nineteen genera of phytoplankton were found in Haruku Strait during the study period. The phytoplankton abundance varied between 4,5 x 102 – 1,65 x 103 cells/l. Phytoplankton consists of Bacillariophyceae (Diatom) with 63% of the total genera, Dinoflagellata with 32 % of the total genera, and Cyanobacteria with 5%, while Chaetoceros, Rhizosolenia, Gonyaulax, Coscinodiscus, and Ceratium were the predominant phytoplankton genera in this area. The distribution pattern forms 8 groups. [ABSTRACT FROM AUTHOR]

The planktonic dinoflagellate Prorocentrum compressum is widespread in warm and temperate seas. A strain identified as P. cf. compressum BEA 0681B isolated from the island of Gran Canaria, NE Atlantic Ocean, showed a divergence in rDNA/ITS phylogenies with respect to P. compressum. The Canarian strain was oval, with an average length‐to‐width ratio of 1.35, smooth thecal surface with less than 150 thecal pores, including oblique pores, sometimes with a bifurcated opening. In contrast, P. compressum was rounder, with a length‐to‐width ratio < 1.2, with reticulate‐foveate ornamentation and 200–300 pores per valve. We propose Prorocentrum canariense sp. nov. These species clustered as the most early‐branching lineage in the clade Prorocentrum sensu stricto. Although this clade mainly contains planktonic species, the closer relatives were the benthic species P. tsawwassenense and P. elegans. Interestingly, P. compressum and P. canariense sp. nov. are widely distributed in temperate and warm seas without an apparent morphological adaptation to planktonic life. The formation of two concentric hyaline mucilaginous walls could contribute to this success. We discuss the use of Prorocentrum bidens to solve the nomenclature issue of P. compressum that was described citing a diatom as basionym. [ABSTRACT FROM AUTHOR]

Thermal stress causes the overproduction and toxic accumulation of reactive oxygen species (ROS), which seems to be correlated with coral bleaching and, ultimately, death. The reduction of ROS concentration within the coral holobiont could minimize the effects of thermal stress and support efforts to reduce coral decline globally. In the current study, we explored the physiological responses of Pocillopora damicornis to ROS-scavenging bacteria inoculation as well as the microbiome restructuring that correlates with P. damicornis's resilience to thermal stress after probiotic inoculation. Inoculation of corals with ROS-scavenging bacteria enhanced coral health and reduced ROS concentration. Furthermore, the enhanced coral thermal resistance promoted by ROS-scavenging bacteria was also correlated with an overall coral microbiome restructuring. In addition, the complex network relationships between bacteria and Symbiodiniaceae in corals after ROS-scavenging bacteria inoculation contributed to corals' resilience to high temperatures. Besides, coral heat tolerance bacterial biomarkers, such as Myxococcota, were enriched in corals with added ROS-scavenging bacteria. Collectively, our findings validate the selected ROS-scavenging bacteria as coral probiotics that could help corals resist thermal stress on a short timescale. Additionally, our data contribute to our understanding of the potential interactions between different members of the coral holobiont and the use of probiotics as tools to aid coral restoration efforts. [ABSTRACT FROM AUTHOR]

Marine dinoflagellate species in the genus Alexandrium are well known to produce paralytic shellfish poison as well as common coastal species with cosmopolitan distribution. However, few studies on the feeding of copepods on Alexandrium species have been conducted. The toxic dinoflagellate Alexandrium pseudogonyaulax contains goniodomin A and causes red tides in many countries. To investigate the relationship between the toxic dinoflagellate A. pseudogonyaulax and the calanoid copepods Acartia spp., we quantified the ingestion rates of Acartia spp. feeding on A. pseudogonyaulax as a function of prey concentration. Additionally, we estimated grazing coefficients by integrating data from field observations of Acartia spp. and coexisting A. pseudogonyaulax with laboratory measurements of ingestion rates obtained during this investigation. Furthermore, we compared the ingestion rates of Acartia spp. and other predators feeding on Alexandrium species as previously reported. The ingestion rates of Acartia spp. on A. pseudogonyaulax increased continuously with increasing mean prey concentration. The highest values among the ingestion rate of Acartia spp. feeding on A. pseudogonyaulax was 3,407 cells predator-1 d-1 (4,872 ng C predator-1 d-1) at the given prey concentration. The calculated grazing coefficients for Acartia spp. on A. pseudogonyaulax in Shiwha Bay, Korea, were up to 0.073 d-1. The results of this study suggest that A. pseudogonyaulax may decrease or maintain the population of Acartia spp. in marine food webs. [ABSTRACT FROM AUTHOR]

Microorganisms have inhabited the oceans since the dawn of Earth. Some of them have organic walls and some produce mineral tests that are usually composed of carbonate minerals or silica. They can therefore be preserved with original parts during sedimentary deposition or fossilized through permineralization or carbonization processes. The most common marine fossil groups studied by micropaleontologists are cyanobacteria, coccolithophores, dinoflagellates, diatoms, silicoflagellates, radiolarians, foraminifers, red and green algae, ostracods, and pteropods. Dormant or reproductive cysts can also be used for determinations of the fossil microbiota. Microfossils can be studied in petrographic slides prepared from rocks or separated from loosely consolidated rocks by disaggregation or dissolution and wet sieving. Their presence is sometimes recognized by biomarkers. Transmitted light microscopy and reflected light stereomicroscopy are necessary for micropaleontological studies whereas scanning electronic microscopy (SEM) aids research on the tiniest fossils and reveals fine skeletal details. Microorganisms have influenced the oxygenation of water and the atmosphere, as well as Earth's carbon cycle and have contributed to the formation of sedimentary rocks. By studying microfossils, paleontologists depict the age of the rock and identify depositional environments. Such studies help us recognize periods of stress in Earth's history and understand their influence on living organisms. Biogenic rocks, made of microfossils, can be used as raw materials, such as fossil fuels, building stone, or additives for the food industry, agricultural, or cosmetic purposes. [ABSTRACT FROM AUTHOR]

Copyright of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Ürünleri Dergisi is the property of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Urunleri Dergisi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Phytoplankton not only acts as a water quality indicator but is also useful for biomonitoring of lentic freshwater bodies. Hence, the present study was attempted to analyse the phytoplankton composition during the four seasons of the year. Results of the present study indicate that phytoplankton were represented by 46 species belonging to Cyanophyceae, Chlorophyceae, Bacillariophyceae, Euglenophyceae and Dinophyceae. Among the various groups, Cyanophyceae dominated in terms of percentage followed by Chlorophyceae, Bacillariophyceae, Euglenophyceae and Dinophyceae. Dinophyceae was recorded only during the presummer and rainy season. The present study recorded the presence of organisms like Anabaena and Microcystis, which indicates eutrophication; Oscillatoria which indicates the presence of high organic matter and low oxygen level as well as Ceratium which indicates pollution. [ABSTRACT FROM AUTHOR]

Due to the creation of biotoxins, marine benthic dinoflagellates have caused many concerns in the ecological, economic, and health sectors. The occurrence of marine toxic microalgae blooms has increased and has caused prevalent poisoning in humans. Many dinoflagellates are benthic and epiphytic, in the sense that they usually live on the bottom of coastal areas or coral reefs and macroalgae, and during widespread blooms, because of their proximity to the coast, they can cause widespread health and economic damage. In addition, by entering the food web, dinoflagellates can spread from small organisms (such as zooplankton) to the bodies of larger aquatic organisms (such as fish), thus threatening human health. The current study was conducted to study the potential risks of dinoflagellates causing harmful algal blooms as species with the potential to produce toxins. The findings of this study showed that 80 phytoplankton species have the potential to produce poison, of which 20 benthic species cause the strongest marine biotoxins, which are deadly for aquatic animals and humans. The most dangerous of these biotoxins include gomyautoxin, brevetoxins, saxitoxin, palytoxin, yessotoxins, maitotoxins, ciguatoxins, okadaic acid, and azaspiracid, which cause widespread death of aquatic organisms in case of harmful algal blooms, and cause acute and fatal poisoning if they enter the human body. The findings of the review of previous research clearly show the notability of knowing benthic toxic dinoflagellates and the requirement to include them in monitoring programs for harmful algal blooms on beaches. [ABSTRACT FROM AUTHOR]

Arctic phytoplankton are highly sensitive to seawater physical and chemical conditions, especially in the context of rapid climate change and sea ice loss. We studied the spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores, and clarified their associations with light, temperature and nutrients in the western Barents Sea in late summer 2017, and winter, spring and early summer 2018. Diatoms, composed mainly of Chaetoceros, Fragilariopsis and Thalassiosira, bloomed in spring at the southern border of the marginal ice zone with mean abundance of 1.1 × 106 cells L−1 and biomass of 119.5 µg C L−1, and were observed to follow the retreat of sea ice in the Arctic water to the north at the shelf break near Nansen Basin, contributing to the progression of the summer situation. Dinoflagellates flourished in surface waters south of Svalbard in summer, with maxima of 2.2 × 105 cells L−1 and 78.2 µg C L−1. High abundances and calcite mass of coccolithophores were detected in the southern Barents Sea and southwest of Svalbard in summer, with maxima of 3.3 × 105 cells L−1 and 4.7 µg C L−1. Two distinct phytoplankton assemblages, closely linked with Atlantic water and Arctic water, were geographically separated by the Polar Front in two summers, with a percent similarity below 11.9%, suggesting great influence of the two water masses on large-scale distributions of phytoplankton. Redundancy analysis revealed that temperature was one of the most important factors in shaping the seasonal distributions of diatoms, while irradiance showed positive correlation with dominant dinoflagellates of each season. From the perspectives of phytoplankton composition and carbon biomass, our findings highlight the governing effect of physical seawater conditions on driving seasonal patterns of phytoplankton biogeography, as well as the pivotal role of nutrients in supporting the phytoplankton growing seasons in the western Barents Sea. [ABSTRACT FROM AUTHOR]

The sea ice spring bloom is crucial for sustaining Arctic marine food webs, with sea ice algae serving as primary carbon sources for higher trophic levels. Despite the prevailing dominance of diatom species in sea ice spring blooms, our study highlights a notable deviation, showcasing a bloom driven by dinoflagellates. Through field sampling of first-year sea ice cores and subsequent analysis of physical and biogeochemical parameters, combined with amplicon sequencing of the 18S rRNA gene, we investigated the occurrence and implications of this significant dinoflagellate bloom, with a particular focus on Polarella glacialis. Our findings reveal that high irradiances at the top of the ice core, coupled with elevated nutrient availability and warm ice conditions, are key drivers of this phenomenon, as elucidated by redundancy analysis. Moreover, our results suggest a potential climate-driven decline in snow cover on sea ice, increased open leads, and thinner sea ice, which may favor the proliferation of dinoflagellates over diatoms. This alternative dinoflagellate-dominated bloom could have profound ecological consequences, given the enriched omega-3 fatty acid content of dinoflagellates, thereby influencing energy transfer within the Arctic marine food web. Furthermore, our study identifies the presence of not only Polarella glacialis but also Chytridinium, an ectoparasite on copepod eggs, and the green algae Ulothrix in relatively high abundances within the sea ice. These findings shed light on the intricate interplay between environmental factors and microbial community dynamics within Arctic sea ice ecosystems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Beibu Gulf is an important semi-enclosed bay located in the northwestern South China Sea, and is famous for its high bio-productivity and rich bio-diversity. The fast development along the Beibu Gulf Economical Rim has brought pressure to the environment, and algal blooms occurred frequently in the gulf. In this study, surface water samples and micro-plankton samples (20-200 µm) were collected in the northern Beibu Gulf coast. Diversity and distribution of eukaryotic planktonic microalgae were analyzed by both metabarcoding and microscopic analyses. Metabarcoding revealed much higher diversity and species richness of microalgae than morphological observation, especially for dinoflagellates. Metabarcoding detected 144 microalgal genera in 8 phyla, while microscopy only detected 40 genera in 2 phyla. The two methods revealed different microalgal community structures. Dinoflagellates dominated in microalgal community based on metabarcoding due to their high copies of 18 s rRNA gene, and diatoms dominated under microscopy. Altogether 48 algal bloom and/or toxic species were detected in this study, 34 species by metabarcoding and 19 species by microscopy. Our result suggested a high potential risk of HABs in the Beibu Gulf. Microalgal community in the surface water samples demonstrated significantly higher OTU/species richness, alpha diversity, and abundance than those in the micro-plankton samples, although more HAB taxa were detected by microscopic observations in the micro-plankton samples. Furthermore, nano-sized taxa, such as those in chlorophytes, haptophytes, and chrysophyceans, occurred more abundantly in the surface water samples. This study provided a comprehensive morphological and molecular description of microalgal community in the northern Beibu Gulf. [ABSTRACT FROM AUTHOR]

Blooms of the harmful dinoflagellate Karenia brevis on the West Florida Shelf (WFS), Gulf of Mexico, are hypothesized to initiate in association with the colonial cyanobacterium Trichodesmium spp. and benefit from dissolved organic nitrogen (DON) release derived from N2-fixation by the cyanobacteria. Previous studies have detected DON release using direct experimental measurements, but there have been few studies that have followed nutrient release by in situ blooms of Trichodesmium and the associated plankton community. It was determined that long-term Trichodesmium spp. and Karenia brevis abundances on the WFS were related, following a 2-month lag. A separate Eulerian study of a Trichodesmium erythraeum bloom event was conducted over 9 days on the Great Barrier Reef. Concentrations of T. erythraeum increased over the course of the study, with coincident increases in dinoflagellate abundance and decreases in diatom abundance. Inside the bloom, concentrations of NH4+, PO43−, and DON increased significantly. The copepod grazer Macrosetella gracilis also increased in abundance as T. erythraeum numbers increased, contributing to nutrient release. Copepod grazing rates were measured, and N release rates estimated. Together, these studies show that Trichodesmium blooms have consequences for dinoflagellate abundance at both seasonal and ephemeral scales via direct and indirect N release. [ABSTRACT FROM AUTHOR]

The diversity of marine cyanobacteria has been extensively studied due to their vital roles in ocean primary production. However, little is understood about the diversity of cyanobacterial species involved in symbiotic relationships. In this study, we successfully sequenced the complete genome of a cyanobacterium in symbiosis with Citharistes regius, a dinoflagellate species thriving in the open ocean. A phylogenomic analysis revealed that the cyanobacterium (CregCyn) belongs to the marine picocyanobacterial lineage, akin to another cyanobacterial symbiont (OmCyn) of a different dinoflagellate closely related to Citharistes. Nevertheless, these two symbionts are representing distinct lineages, suggesting independent origins of their symbiotic lifestyles. Despite the distinct origins, the genome analyses of CregCyn revealed shared characteristics with OmCyn, including an obligate symbiotic relationship with the host dinoflagellates and a degree of genome reduction. In contrast, a detailed analysis of genome subregions unveiled that the CregCyn genome carries genomic islands that are not found in the OmCyn genome. The presence of the genomic islands implies that exogenous genes have been integrated into the CregCyn genome at some point in its evolution. This study contributes to our understanding of the complex history of the symbiosis between dinoflagellates and cyanobacteria, as well as the genomic diversity of marine picocyanobacteria. [ABSTRACT FROM AUTHOR]

The dinoflagellate Alexandrium catenella is a well-known paralytic shellfish toxin producer that forms harmful algal blooms, repeatedly causing damage to Chilean coastal waters. The causes and behavior of algal blooms are complex and vary across different regions. As bacterial interactions with algal species are increasingly recognized as a key factor driving algal blooms, the present study identifies several bacterial candidates potentially associated with Chilean Alexandrium catenella. This research narrowed down the selection of bacteria from the Chilean A. catenella culture using antibiotic treatment and 16S rRNA metabarcoding analysis. Subsequently, seawater from two Chilean coastal stations, Isla Julia and Isla San Pedro, was monitored for two years to detect Alexandrium species and the selected bacteria, utilizing 16S and 18S rRNA gene metabarcoding analyses. The results suggested a potential association between Alexandrium species and Spongiibacteraceae at both stations. The proposed candidate bacteria within the Spongiibacteraceae family, potentially engaging in mutualistic relationships with Alexandrium species, included the genus of BD1-7 clade, Spongiibbacter, and Zhongshania. [ABSTRACT FROM AUTHOR]

Benthic dinoflagellates have been the subject of extensive taxonomic research in recent decades. Studies of morphologies of already known species of benthic dinoflagellates from various geographical populations remain relevant, as these allow elucidation of some details that were overlooked in the original species descriptions or assessment of their morphological variability. In the present study, two rare species of dinoflagellates, Amphidiniella sedentaria and Pachena cf. leibnizii, have been studied, for the first time, from coastal sands of the northwestern Sea of Japan. In the cells of A. sedentaria from the Sea of Japan, we have found two anterior intercalar plates instead of one. Therefore, the original formula has been changed to APC 4′ 2a 7″ 5c 4s 6‴ 2⁗. As a result of the examination of P. cf. leibnizii from the Sea of Japan, we have counted seven precingular plates and six cingular plates, instead of six and five, respectively, indicated in the original description. The plate formula of the cells of P. cf. leibnizii from the Sea of Japan is APC 4′ 3a 7″ 6c 5s 5‴ 2⁗. It is currently difficult to judge whether these differences are morphological variations. Therefore, we have identified these cells as P. cf. leibnizii. [ABSTRACT FROM AUTHOR]

Many dinoflagellate species are bioluminescent, which is one of the anti-predation mechanisms in these species. In addition, dinoflagellate species experience a wide range of salinities in the ocean. However, the effects of salinity on their bioluminescence intensity has only been investigated for one species. Here, we explored the effect of salinity on the bioluminescence intensity of the heterotrophic dinoflagellate Noctiluca scintillans NSDJ2010 feeding on the chlorophyte Dunaliella salina, the heterotrophic dinoflagellate Polykrikos kofoidii PKJH1607 feeding on the dinoflagellate Alexadrium minutum, and the autotrophic dinoflagellate Alexandrium mediterraneum AMYS1807. Moreover, to determine the cell volume and growth effects on bioluminescence intensity, the cell volume and growth rate of three bioluminescent dinoflagellates were simultaneously investigated. The mean 200-s-integrated bioluminescence intensity (BL) per cell, equivalent to the total bioluminescence, of N. scintillans, P. kofoidii, and A. mediterraneum was significantly affected by salinity and increased with increasing salinity from 10 to 40. The results of the present study suggest that the total bioluminescence of N. scintillans, P. kofoidii, and A. mediterraneum in offshore and oceanic waters is greater than that in estuarine waters. [ABSTRACT FROM AUTHOR]

Dinoflagellates are marine organisms that undergo seasonal proliferation events known as algal blooms. Vegetative cell proliferation is a main contributing factor in these events. However, mechanistical understanding of mitosis and cytokinesis in dinoflagellates remains rudimentary. Using an optimized immunofluorescence protocol, we analysed changes in microtubule organization occurring during the mitotic cycle of the toxic dinoflagellate Ostreopsis cf. ovata. We find that the flagella and the cortical microtubule array persist throughout the mitotic cycle. Two cytoplasmic microtubule bundles originate from the ventral area, where the basal bodies are located - a cortical bundle and a cytoplasmic bundle. The latter associates with the nucleus in the cell centre before mitosis and with the acentrosomal extranuclear spindle during mitosis. Analysis of tubulin post-translational modifications identifies two populations of spindle microtubules - polar acetylated microtubules, whose length is constant, and central tyrosinated microtubules, which elongate during chromosome segregation. During cell division a microtubule-rich structure forms along the dorsal-ventral axis, associated with the site of cytokinesis, consistent with a cytokinetic mechanism that is independent of the actomyosin ring typical of animal and yeast cells. [ABSTRACT FROM AUTHOR]

Despite the fact that the first red tide reported on the coasts of the Iberian Peninsula was due to Lingulodinium polyedra, knowledge about their frequency and, particularly, about the environmental conditions contributing to bloom initiation is still scarce. For this reason, L. polyedra bloom episodes were observed and studied in three Galician rias during the summer season based on the 1993–2008 record database period; additionally, samples were collected in summer 2008. Proliferations of L. polyedra occurred in the rias of Ares and Barqueiro in June and August, respectively, while in the Ria of Coruña, they persisted from the end of June to early September. Red tides developed when the surface temperature reached 17 °C, with "seasonal thermal window" conditions, and when salinities were ≥30, i.e., an "optimal salinity window"; when these parameters were lower than these thresholds, cyst germination decreased. A cyst transport mechanism from sediments to the surface must also exist; this mechanism was found to be natural (tidal currents) in the ria of Barqueiro or anthropogenic (dredging) in the rias of Ares and Coruña. Surface temperatures during summer were usually favorable for cyst germination (85 to 100%) during the 1993–2008 period; however, water temperatures below 10 m depth only rarely reached the 17 °C threshold (2 to 18%). During this 16-year period, dredging activities could explain 71% (Coruña) and 44% (Ares) of the recorded bloom events. When a bloom episode developed in early summer, favorable conditions did not lead to a new red tide, probably due to the lag period required by cysts for germination. Moreover, blooms did not develop when high densities of diatoms (>1,000,000 cells·L−1) remained in the water column as a result of summer upwelling pulses occurring in specific years. The temperature–sediment disturbance pattern found in this study provides a useful tool for the prevention of eventual risks resulting from red tides of this dinoflagellate. [ABSTRACT FROM AUTHOR]

This study was conducted in Shizugawa Bay, located on the north-eastern coast of Japan, to determine phytoplankton assemblages. Metabarcoding with the PsbA gene and environmental surveys were conducted from May 2021 to January 2022. PCA results showed that phytoplankton assemblages changed with the environmental parameters, such as water temperature and salinity, indicating a clear seasonal pattern. The relative abundance was dominated by Chlorophyta (annual mean 34.9%) > Bacillariophyta (29.1%) > Haptophyta (17.8%) > Dinophyceae (11.7%). It is suggested that many species of Chlorophyta remain without being filtered by shellfish because the dominant representatives were pico-prasinophytes, which are of small size and are difficult for shellfish to capture. Bacillariophytes are thought to have been consumed preferentially since they are known to be a good food source for adult shellfish. Among Dinophyceae, Dinophysis spp. (causing diarrheal poisoning) were dominant throughout the period, while Alexandrium spp. (causing paralytic poisoning) showed relatively low abundance. Phaeocystis spp. (including some toxic species) were the dominant haptophytes. Cyanobacteria tended to appear particularly in summer although their mean relative abundance was less than 3%. Although the data are limited, they provide a useful snapshot of phytoplankton assemblages in Shizugawa Bay and the environmental factors that affect them. [ABSTRACT FROM AUTHOR]

The toxin‐producing dinoflagellate Alexandrium pseudogonyaulax has become increasingly abundant in northern European waters, replacing other Alexandrium species. A. pseudogonyaulax produces goniodomins and lytic substances, which can be cytotoxic toward other organisms, including fish, but we still know little about the environmental conditions influencing its growth and toxicity. Here, we investigated the impacts of different nitrogen sources and light intensities, common bottom‐up drivers of bloom formation, on the growth and toxin content of three A. pseudogonyaulax strains isolated from the Danish Limfjord. While the growth rates were significantly influenced by nitrogen source and light intensity, the intracellular toxin contents only showed strong differences between the exponential and stationary growth phases. Moreover, the photophysiological response of A. pseudogonyaulax showed little variation across varying light intensities, while light‐harvesting pigments were significantly more abundant under low light conditions. This study additionally highlights considerable physiological variability between strains, emphasizing the importance of conducting laboratory experiments with several algal strains. A high physiological plasticity toward changing abiotic parameters points to a long‐term establishment of A. pseudogonyaulax in northern European waters. [ABSTRACT FROM AUTHOR]