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Harmful blooms of the toxic dinoflagellate Ostreopsis cf. ovata have been a recurrent phenomenon along the Mediterranean coasts in the last decades. Since first recorded, there has been a widespread belief that the extension of this dinoflagellate, well-known in tropical areas, to higher latitudes was due to global warming and the general rise of seawater temperature. Blooms of O. cf. ovata along the Conero Riviera (northern Adriatic Sea) occur between the end of the summer and the beginning of the autumn since 2006. The Ostreopsis cf. ovata abundances collected from its first record to today were analysed to better define the interannual trend of this phenomenon and its possible linking to certain climate change predictors. A significant increasing trend in the magnitude of Ostreopsis phenomenon was observed up to year 2012, then a stabilization at relatively low values was observed. This trend does not follow the incessant increase in water temperature observed during the last three decades in the Adriatic Sea, but rather recalls patterns seen in invasive species, although the provenience of O. cf. ovata in the Mediterranean Sea is still unresolved. Even if the Ostreopsis bloom in this area seems to slightly lessen in the last decade, Ostreopsis abundances still reach values of up to 103 cells cm−2 which could be harmful to human health. [ABSTRACT FROM AUTHOR]

In the framework of benthic harmful algal bloom monitoring, the most common sampling strategy is based on the collection of macroalgae, and the abundance of epiphytic microalgae are mainly expressed as cells g−1 macroalgal fresh weight (fw). However, this methodology has some inherent problems, due to (i) the thallus-specific weights that markedly differ among algal species, (ii) the thallus architecture, and (iii) the production of allelopathic compounds that affects the epiphyte abundances among macroalgae, irrespective of the available colonizable surface. This study proposes a method to compare the abundances of Ostreopsis cf. ovata cells on different substrata, using a conversion factor that converts the abundances expressed as cells g−1 fw (or dry weight) to cells cm−2. Expressing abundances in terms of cells cm−2, the abundances can be compared (i) among different macroalgal species and (ii) between macroalgae and other substrata (such as rocks, pebbles, or shellfish shells). We also propose to normalize abundances when different macroalgae are sampled throughout the bloom period, considering the different epiphyte loads of different macroalgal species regardless of the available surface area. [ABSTRACT FROM AUTHOR]

The emerging threat of ciguatera poisoning (CP) in Europe has been associated with fish captured in the Canary Islands (Spain) and Selvagens Islands (Portugal). The first are heavily populated islands where numerous scientific studies have been carried out. Conversely, the Selvagens Islands as a nature reserve with low human pressure have been rarely surveyed in terms of the marine benthic microalgae, including the epiphytic ciguatera-causing dinoflagellate species. To investigate the harmful microalgal diversity of the Selvagens Islands, a scientific cruise to these remote islands took place in September, 2018. The Gambierdiscus species composition and distribution, and the associated epiphytic dinoflagellate community, were assessed using artificial substrate devices. Gambierdiscus cells were found in all samples, reaching concentrations of up to 725 cells 100 cm–2. G. australes was the only species identified after morphological and molecular analysis of the retrieved cultures. Species identification was confirmed by molecular characterization based on the LSU D8–D10 region. Nevertheless, phylogenetic studies indicated that some strains diverged from the G. australes clade suggesting genetic differentiation. Toxicity was estimated by neuro-2a cell-based assay in four strains, ranging from 2.46–83 fg of CTX1B eq. cell–1. The epiphytic dinoflagellate community that co-occurred with Gambierdiscus comprised other toxic or potentially toxic dinoflagellates, such as Ostreopsis, Prorocentrum, Amphidinium and Coolia species. Oceanographic and meteorological data were also obtained to characterize the occurrence of Gambierdiscus. This study is the first stage in understanding the role of the Selvagens Islands in the incubation and proliferation of the ciguatera-causing dinoflagellates Gambierdiscus in the NE Atlantic. The Selvagens Islands are a ciguatera hotspot in Europe. Gambierdiscus australes was the only species observed in the Selvagens Islands. Strains diverging from the G. australes clade suggest genetic differentiation. [ABSTRACT FROM AUTHOR]

Species of the marine benthic dinoflagellate genus Gambierdiscus Adachi & Fukuyo are morphologically similar, and DNA based sequence analyses are necessary to complement morphological species determination. Gambierdiscus species may produce ciguatoxins, the causative agents of human illness ciguatera poisoning (CP). In this study, morphological descriptions, based on laboratory cultures, using light and scanning electron microscopy and DNA based characterisation of one strain (ISOG4) isolated from Petite Rivière Noire, Mauritius are provided. Our morphological observations coupled with DNA based sequence analyses indicate that the Mauritian strain is Gambierdiscus caribaeus Vandersea, Litaker, M.A.Faust, Kibler, W.C.Holland & P.A.Tester. Our strain bears close similarity (LSU 99% identity) to Gambierdiscus caribaeus (GenBank[KY448444]) isolated from Canary Islands, Spain, and phylogenetic results depict it as sister to G. jejuensis S.H.Jang & H.J.Jeong. Gambierdiscus caribaeus (ISOG4) is herein a first report from Mauritius Island and the Mascarene region. Caractérisation moléculaire et morpho-taxonomie de Gambierdiscus caribaeus Vandersea, Litaker, M.A.Faust, Kibler, W.C.Holland & P.A.Tester (Dinophyceae) de l'île Maurice, sud-ouest de l'océan Indien. Les espèces du genre de dinoflagellés benthiques marins Gambierdiscus Adachi & Fukuyo sont morphologiquement similaires, et des analyses de séquences basées sur l'ADN sont nécessaires pour compléter la détermination morphologique des espèces. Les espèces de Gambierdiscus peuvent produire des ciguatoxines, agents responsables de la maladie humaine qu'est la ciguatera (CP). Dans cette étude, des descriptions morphologiques, basées sur des cultures en laboratoire, réalisées par microscopie optique et électronique à balayage, et une caractérisation basée sur l'ADN d'une souche (ISOG4) isolée de Petite Rivière Noire, Maurice sont fournies. Nos observations morphologiques couplées aux analyses de séquences basées sur l'ADN indiquent que la souche mauricienne est Gambierdiscus caribaeus Vandersea, Litaker, M.A.Faust, Kibler, W.C.Holland & P.A.Tester. Notre souche est très similaire (LSU 99 %) à Gambierdiscus caribaeus (GenBank[KY448444]) isolé des îles Canaries, Espagne, et les résultats phylogénétiques la décrivent comme sœur de G. jejuensis S.H.Jang & H.J.Jeong. Gambierdiscus caribaeus (ISOG4) est ici signalé pour la première fois à l'île Maurice et dans la région des Mascareignes. [ABSTRACT FROM AUTHOR]

This study elucidates the responses of bloom-forming benthic dinoflagellates, Amphidinium carterae and Bysmatrum gregarium (formerly known as B. caponii) to salinity changes and prolonged darkness. Both dinoflagellates are known to inhabit rock pools that experiences significant variations in environmental conditions. In both dinoflagellates, salinity changes did not trigger cyst formation but morphological responses were different under prolonged darkness. B. gregarium underwent encystment while A. carterae showed cell shrinkage and flagella movement (up to 9 days) without cell division. This study documents cyst formation in B. gregarium for the first time. However, both dinoflagellates showed reduced growth and photosynthetic efficiency under lower salinity (< 5) and prolonged darkness. Interestingly, both dinoflagellates did not show a maximum photosynthetic efficiency of 0.65 under optimal growth conditions which could be due to the prevalence of carotenoid-chlorophyll protein complex and diatoxanthin (fluorescence quencher). This study proposes that seasonal rainfall (e.g., Southwest monsoon along the Indian coast) can control the proliferation of both dinoflagellates in rock pools (i.e., just before the onset of monsoonal rainfall) as it hampers cell growth, inhibits photosynthesis, and does not induce cyst formation as adaptive survival strategies. Further findings on their dark survival for several days will have implications in the studies related to the transportation to different locations through the ship's ballast water discharge or to deeper sediments in the intertidal regions. [ABSTRACT FROM AUTHOR]

Benthic dinoflagellates have attracted increasing attention in recent years because of their toxicity and ability to form extensive harmful algal blooms. Ostreopsis producing palytoxin and its analogs, Gambierdiscus producing ciguatera toxins, and Prorocentrum producing okadaic acid and dinophysis toxins, have been concerned as serious human poisonings. We explored the benthic dinoflagellate biodiversity and distribution characteristics of a series of tropical reefs in 20–40-m water depth in wet season in the Zhongsha Islands in South China Sea using morphological, phylogenetic, and cell counting methods. Results show that benthic dinoflagellates in the islands are rich in biodiversity and 15 species from genera Amphidinium, Coolia, Ostreopsis, and Prorocentrum were identified: Amphidinium carterae, A. magnum, A. massartii, A. operculatum, Coolia canariensis, C. malayensis, C. palmyrensis, C. tropicalis, Ostreopsis cf. ovata, Prorocentrum concavum, P. cf. sculptile, P. emarginatum, P. hoffmannianum, P. lima, and P. rhathymum. Among them, A. magnum is reported for the first time in Chinese waters. The abundance of benthic dinoflagellates was relatively low at 88–4 345 cells/100 cm2 on sediment and 10–91 cells/g on macroalgae. Prorocentrum and Amphidinium were the dominant and subdominant genera, respectively. It is speculated that the low abundance of benthic dinoflagellates is closely related to the scarcity of macroalgae and stronger water motion at the depth >15 m in Zhongsha Islands. This study expanded the study in biodiversity of benthic dinoflagellates in Chinese waters, and revealed the distribution characteristics of harmful benthic microalgae in reef habitats. [ABSTRACT FROM AUTHOR]

Intense blooms of the toxic dinoflagellate Ostreopsis producing palytoxin (PlTX) analogs, mainly ovatoxins (OVTXs), have been a recurrent phenomenon along several Mediterranean coasts. Although there is evidence of seafood contamination by these toxins, the dynamics of their bioaccumulation during Ostreopsis blooms is not yet clear. Toxin concentrations in wild mussels at two sites in the Conero Riviera, along the northern Adriatic Sea (Portonovo and Passetto), were analyzed from August to October 2021, throughout an Ostreopsis cf. ovata bloom, to investigate their relationships with the bloom pattern and abundances. Contaminated mussels showed the typical toxin profile dominated by OVTX-a and -b, with levels lower than the threshold considered unsafe for human consumption (30 µg PlTX-equivalent kg−1 soft tissue). The toxin content reached 36.4 µg PlTX kg−1 soft tissue only in a single sampling date. A clear correlation between the bioaccumulation of OVTXs in mussels and the abundance of Ostreopsis was observed. Our results highlighted, however, that bioaccumulation in the mussels is not affected merely by the abundance of toxic microalgae, since higher toxin levels were recorded at Portonovo, where the cell abundances were lower than at Passetto. The results from this study indicate that the Italian guidelines for the management of Ostreopsis blooms in bathing waters are also useful in managing the risks of human intoxication through ingestion, as mussel contamination was detected only during the alert phase (10,000–30,000 cells L−1). [ABSTRACT FROM AUTHOR]

• The impact of microplastics on marine benthic dinoflagellates was studied. • PS had limited effect on the growth of P. lima , but enhanced OA and EPS production. • Genes related to toxin and carbohydrate synthesis, and metabolism were upregulated. • Increased DSP toxins may strengthen the threat of benthic dinoflagellates. Microplastics are well known as contaminants in marine environments. With the development of biofilms, most microplastics will eventually sink and deposit in benthic environment. However, little research has been done on benthic toxic dinoflagellates, and the effects of microplastics on benthic dinoflagellates are unknown. Prorocentrum lima is a cosmopolitan toxic benthic dinoflagellate, which can produce a range of polyether metabolites, such as diarrhetic shellfish poisoning (DSP) toxins. In order to explore the impact of microplastics on marine benthic dinoflagellates, in this paper, we studied the effects of polystyrene (PS) on the growth and toxin production of P. lima. The molecular response of P. lima to microplastic stress was analyzed by transcriptomics. We selected 100 nm, 10 μm and 100 μm PS, and set three concentrations of 1 mg L −1, 10 mg L −1 and 100 mg L −1. The results showed that PS exposure had limited effects on cell growth, but increased the OA and extracellular polysaccharide content at high concentrations. After exposure to PS MPs, genes associated with DSP toxins synthesis, carbohydrate synthesis and energy metabolism, such as glycolysis, TCA cycle and pyruvate metabolism, were significantly up-regulated. We speculated that after exposure to microplastics, P. lima may increase the synthesis of DSP toxins and extracellular polysaccharides, improve the level of energy metabolism and gene expression of ABC transporter, thereby protecting algal cells from damage. Our findings provide new insights into the effects of microplastics on toxic benthic dinoflagellates. [ABSTRACT FROM AUTHOR]

• Ostreopsis abundances were quantified at the micro and mesohabitat scale and on artificial macroalgal mimics in two study sites. • Ostreopsis cell assessment can vary in function of the scale (micro and mesohabitat). • The substrate's preferences diminish when cell abundances are very high, while in moderate blooms it is possible to appreciate differences in abundances among substrates. • Higher densities of Ostreopsis cells were associated with Dictyota fasciola in one of the sampling sites. Harmful Algal Blooms (HABs) are increasing in temperate areas, and the growth rates of benthic harmful dinoflagellates may be favoured in the context of global climate change. Benthic dinoflagellates, including species belonging to the Ostreopsis Schmidt genus, are known to develop on the surface of macroalgae and different macroalgal morphotypes and communities could host higher or lower cell abundances. The physical structure of the macroalgal substrate at the small scale (cm, microhabitat scale) and the structural complexity of the macroalgal community at the medium scale (few m, mesohabitat scale) could play a relevant role in bloom facilitation: the hypothesis that Ostreopsis species could be associated with macroalgal turfs and shrubs, structurally less complex communities than canopy-forming macroalgae, is especially under discussion and, if confirmed, could link bloom occurrence to regime shifts in temperate ecosystems. The present study, performed in two locations of the Ligurian Sea (Rochambeau, France and Vernazzola, Italy) aimed at understanding marine vegetation's role at the micro and mesohabitat scales in controlling the distribution and abundance of Ostreopsis. The abundance of the microalgal cells was quantified at different spatial scales, from cm to a few m, on different macroalgal species and communities, including artificial substrates, to tease apart the micro and mesohabitat effects. The results obtained show a high spatio-temporal variability, potentially hiding habitat-related patterns. The substrate's preferences diminish when cell abundances are very high, as in the case of Rochambeau, while in presence of moderate cell abundances as in Vernazzola or the first phases of blooms, it is possible to appreciate differences in abundances among substrates (in our study, Dictyota fasciola (Roth) Lamouroux supporting higher abundances). Our results open new research topics such as the study of blooms at a larger scale (macrohabitat) and testing different sampling methods to standardise the cells' abundances independently on the substrate. [ABSTRACT FROM AUTHOR]

Intense blooms of the toxic dinoflagellate Ostreopsis producing palytoxin (PlTX) analogs, mainly ovatoxins (OVTXs), have been a recurrent phenomenon along several Mediterranean coasts. Although there is evidence of seafood contamination by these toxins, the dynamics of their bioaccumulation during Ostreopsis blooms is not yet clear. Toxin concentrations in wild mussels at two sites in the Conero Riviera, along the northern Adriatic Sea (Portonovo and Passetto), were analyzed from August to October 2021, throughout an Ostreopsis cf. ovata bloom, to investigate their relationships with the bloom pattern and abundances. Contaminated mussels showed the typical toxin profile dominated by OVTX-a and -b, with levels lower than the threshold considered unsafe for human consumption (30 µg PlTX-equivalent kg−1 soft tissue). The toxin content reached 36.4 µg PlTX kg−1 soft tissue only in a single sampling date. A clear correlation between the bioaccumulation of OVTXs in mussels and the abundance of Ostreopsis was observed. Our results highlighted, however, that bioaccumulation in the mussels is not affected merely by the abundance of toxic microalgae, since higher toxin levels were recorded at Portonovo, where the cell abundances were lower than at Passetto. The results from this study indicate that the Italian guidelines for the management of Ostreopsis blooms in bathing waters are also useful in managing the risks of human intoxication through ingestion, as mussel contamination was detected only during the alert phase (10,000–30,000 cells L−1).

Identification of species of the dinoflagellate genus Ostreopsis is difficult because several species have been poorly described, others misidentified in the literature, and the type species, O. siamensis, has not been described by contemporary taxonomic methods. In the present study, it is argued that Ostreopsis sp. 6 as described by previous authors is similar to the type species, and we offer an emended description of O. siamensis by LM, SEM, and molecular analyses of nuclear LSU and ITS rDNA based on material collected a few hundred kilometers from the type locality in the Gulf of Thailand and along the Vietnamese east coast. Ostreopsis siamensis is genetically different from the species reported as O. cf. siamensis in the literature and the latter should be described as a separate species. It is also concluded that with the poor knowledge of the morphological variability of many species of Ostreopsis, O. siamensis may not be distinguished from other similar‐sized species by its morphological features, and hence molecular data are needed for reliable identification. The species Ostreopsislenticularis and Ostreopsis cf. ovata were also found and described. [ABSTRACT FROM AUTHOR]

The effects of different types of ultraviolet (UV) radiation (UVR, wavelength=280–400 nm) and light intensities on cell growth, pigment composition, UV-absorbing compounds (UVACs), and chlorophyll a (Chl a) fluorescence were studied in dinoflagellate Prorocentrum lima cultured outdoors for 16 days and indoors for 18 days. In the outdoor experiment, UVA radiation (320–400 nm) increased the growth rate of this dinoflagellate when solar light intensities were < 12%; decreased growth rates were observed when intensities were> 12%. Exposure to UVB radiation (280–320nm) alleviated the negative effects of UVA. In the indoor experiment, UVA and low doses of UVB enhanced growth rates. Addition of low doses of UVB to UVA exposure resulted in higher contents of Chl a and photoprotective pigments compared with UVA exposure only. The results of both experiments showed that UVB is the primary signal of UVAC synthesis. High-dose UVB exposure accelerated growth rates when UVAC contents were maintained at high levels, suggesting that the latter plays a key role in UVR damage protection. Furthermore, the repair rate was enhanced by UVB exposure after 16 days of culture. This study confirms the positive effects of UVA and UVB on the growth of P. lima, with the latter enhancing the photoprotective and recovery pathways of the species. [ABSTRACT FROM AUTHOR]

Dinoflagellates in the genus Gambierdiscus are known to produce potent neurotoxins known as ciguatoxins. These toxins vector through the food web and can reach sufficiently high levels to cause ciguatera fish poisoning (CFP). In many regions of the Caribbean, little is known about the occurrence of CFP-causing species or the incidence of CFP, despite its apparent regional increase over the last few decades. Given the intraspecific variability in content and potencies of these toxins among Gambierdiscus species, the precise identification of local species of this genus is crucial. In this study we confirm the presence of the epibenthic dinoflagellate Gambierdiscus caribaeus in the Colombian continental Caribbean. Cells were collected in seagrass beds of Thalassia testudinum in Bonito Gordo, a site located on the western side of Bahía Concha, Tayrona National Natural Park, near the city of Santa Marta, Colombia. Subsequently, a single strain of Gambierdiscus could be established for further identification. Morphological (light and scanning electron microscopy), and molecular results (partial LSU and ITS rDNA sequencing) were consistent with the original description of G. caribaeus, as well as with the morphological characteristics shown by other authors in organisms obtained near the sampling area. [ABSTRACT FROM AUTHOR]

Thecadinium ovatum is one of the four species of Thecadinium sensu lato which has no apical pore, but has a ventral pore on the first apical plate, an unusual 'multi-pimple-plate' in the precingular series, and an antapical plate with several spines. Its original thecal plate formula was 3ʹ 6ʹʹ 6c 5s? 5ʹʹʹ 1ʹʹʹʹ. Morphological examination of cells from the Sea of Japan showed that T. ovatum has four apical plates and that the multi-pimple-plate is an anterior intercalary plate. The revised thecal plate formula of the species is 4ʹ1a 5ʹʹ6c 6s 5ʹʹʹ1ʹʹʹʹ. Molecular genetic data of T. ovatum were obtained for the first time. LSU rRNA gene sequences obtained by a single-cell PCR method from natural samples were used for taxonomic and phylogenetic studies. The sequence for T. ovatum did not show a close phylogenetic relationship to sequences of T. yashimaense, T. kofoidii and T. pseudokofoidii. The phylogenetic analysis of the D1/D2 and D8/D10 regions of the large subunit (LSU) rRNA from single cells indicated that Thecadinium ovatum formed the nearest sister branch to the Protoceratiaceae, including Pentaplacodinium usupianum, Pentaplacodinium saltonense, Protoceratium reticulatum, and Ceratocorys species. This clade was placed within the order Gonyaulacales. Consequently, T. ovatum does not belong to Thecadinium sensu stricto, nor does it show a phylogenetic relationship with other Thecadinium sensu lato species (T. yashimaense and Psammodinium inclinatum). Thus, T. ovatum should be transferred to an independent new genus that may be created after genetic information is available for the other morphologically close species. [ABSTRACT FROM AUTHOR]

The toxigenic dinoflagellate Ostreopsis cf. ovata is known to produce a range of palytoxin (PLTX) - related compounds named ovatoxins (OVTX). O. cf. ovata presents a wide variability in toxin production and its toxic profile is strain-specific. Several OVTXs, denominated from -a to -h and -l have been reported from different strains of this benthic microalgae up to now, mainly in Mediterranean isolates. However, less is known about the toxin profile of the strains present in the Atlantic coasts of Europe. In this work, strains of O. cf. ovata isolated from the South coast of Portugal mainland (Algarve) and Selvagens Island (Madeira, Portugal) were cultured and tested for toxicity by hemolytic assay. Toxin profiles were qualitatively elucidated by Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS). The strain from Algarve presented lower toxic potency than the strain from Selvagens island (12.3 against 54.8 pg of PLTX equivalents per cell) showing in both cases the characteristic toxin profile of Mediterranean strains. The major component, OVTX-a, was concomitant with OVTX from -b to -g and isobaric PLTX. Regarding the morphological characteristics of these strains, as well as their toxin fingerprint, it is likely they are closely related to strains from Mediterranean coasts. The present study reports for the first time the occurrence of several OVTX congeners and iso-PLTX in O. cf. ovata from Portuguese waters. This study provides valuable information to characterize the risk of OVTXs-related outbreaks in Portugal. • Toxin profile of two strains of Ostreopsis cf. ovata from Portugal is reported. • Both strains present similar toxin profile but differ in toxic potency. • Blooms of O. cf. ovata in Algarve and Madeira may pose a risk for public health. [ABSTRACT FROM AUTHOR]

Several species of benthic dinoflagellates produce potent toxins that have negative impacts on the economy and human health of coastal zones. In a previous study carried out in a zone known to be prone to ciguatera, located at the eastern end of the Gulf of Batabanó, the species diversity of ciguatoxin producer organism, Gambierdiscus, was determined, however the presence and abundance of other potentially toxic benthic dinoflagellate genera was not considered. In present study, the samples obtained from artificial and natural substrates were re-analyzed to estimate the abundance of other genera of dinoflagellates in the area. The genera Prorocentrum and Ostreopsis were identified at all sampling points. In general, the abundance of these genera showed high variability between sites and were higher compared to the reported abundance of the genus Gambierdiscus. The results obtained by using both types of substrates were similar, which encourages the use of artificial substrates for quantifying benthic dinoflagellates in future studies. This work contributes to the available information about the presence and abundance of potentially toxic benthic dinoflagellates in the southern central region of Cuba and provides basic elements for risk assessment related to toxic blooms of these microalgae. [ABSTRACT FROM AUTHOR]

The present study investigated selected benthic dinoflagellates isolated from different regions from the Western Atlantic, with respect to their morphology, growth, toxicity, and toxin production in culture. A total of nine strains of benthic dinoflagellates belonging to three genera were cultivated: Amphidinium massartii, Amphidinium operculatum (2 strains), Coolia malayensis (2 strains), Prorocentrum hoffmannianum (2 strains), and Prorocentrum mexicanum, whose morphological and genetic characterizations matched previous descriptions, and Prorocentrum sp., morphologically related to P. cf. norrissianum. The two strains of C. malayensis from Brazil attained the highest growth rates (0.42–0.47 day−1), but the lowest cell densities (2.2–2.9 × 104 cells mL−1) in culture. The highest cell densities were recorded for A. massartii from Cuba (3.8 × 105 cells mL−1). All species/strains investigated exhibited moderate toxicity to larvae of the brine shrimp Artemia salina; A. massartii being the most toxic species and Prorocentrum sp. the least one. Additionally, extracts of Prorocentrum species (P. hoffmannianum and Prorocentrum sp.) tested positive in mouse bioassays following intraperitoneal injection. Moderate to high concentrations of okadaic acid (OA), but no dinophysistoxins (DTXs), were found in both P. hoffmannianum strains from Cuba; but no diarrheic toxins were detected in either P. mexicanum from Cuba or Prorocentrum sp. from southern Brazil. Finally, five novel amphidinols were detected in cultures of both A. massartii (Cuba) and A. operculatum (Brazil) by LC-MS/MS, with molecular weights of 1440.8 (two isomers), 1360.8, 1287.7, and 984.6. These findings clearly indicate the need to include benthic species among the harmful microalgae surveyed in regional monitoring programs of phytoplankton. [ABSTRACT FROM AUTHOR]

• 127 growth rate data of O. cf. ovata , 90 of P. lima and 56 of C. malayensis compiled. • Temperature had the greatest effect on species growth rate. • Temperature and salinity were equally important to explain O. cf. ovata growth. • Subclade A of O. cf. ovata and clade 4 of P. lima were the most studied. • Growth data from genetic lineages and regions underrepresented are needed. Benthic dinoflagellates produce potent toxins that may negatively affect humans and the marine biota. Understanding the factors that stimulate their growth is important for management strategies and to reduce their potential negative impacts. Laboratory cultures have been extensively used to study microalgae physiology and characterize life cycles, nutrition, growth rates, among other processes. A systematic review of the literature on the growth parameters of the benthic dinoflagellates Ostreopsis cf. ovata, Prorocentrum lima species complex and Coolia malayensis obtained in laboratory cultures of strains isolated from all over the world was performed. The effects of temperature, light intensity, photoperiod, salinity and culture media on the growth rate of these species were evaluated using multiple regressions and a model selection approach, based on the Akaike Information Criteria (AIC). The potential effects of the initial culture abundance and the media volume used on the growth of the species were also assessed. Data from 50 articles (25 for O. cf. ovata , 21 for P. lima and 6 for C. malayensis), resulting in 399 growth parameter values (growth rate, doubling time and maximum yield) were compiled in a database. The genetic clades of O. cf. ovata and P. lima species complex were also noted. Growth rate was the most frequently reported growth parameter for the three species, and 127 values were retrieved for O. cf. ovata , 90 for P. lima and 56 for C. malayensis. Temperature was the factor that best explained the growth response of P. lima and C. malayensis , whereas for O. cf. ovata , temperature and salinity were equally important. Light intensity and photoperiod were included among the six best models for the studied species but presented a weaker effect on growth. Given the observed and future projected climate change, increasing ocean temperature will promote the growth of these species, likely leading to an expansion of their impacts on ecosystems and human health. The use of common garden experiments using multiple strains from different geographic domains, particularly addressing underrepresented lineages is recommended, as they will provide more balanced insight regarding the species physiological responses to environmental drivers. [ABSTRACT FROM AUTHOR]

Many benthic dinoflagellates are known or suspected producers of lipophilic polyether phycotoxins, particularly in tropical and subtropical coastal zones. These toxins are responsible for diverse intoxication events of marine fauna and human consumers of seafood, but most notably in humans, they cause toxin syndromes known as diarrhetic shellfish poisoning (DSP) and ciguatera fish poisoning (CFP). This has led to enhanced, but still insufficient, efforts to describe benthic dinoflagellate taxa using morphological and molecular approaches. For example, recently published information on epibenthic dinoflagellates from Mexican coastal waters includes about 45 species from 15 genera, but many have only been tentatively identified to the species level, with fewer still confirmed by molecular criteria. This review on the biodiversity and biogeography of known or putatively toxigenic benthic species in Latin America, restricts the geographical scope to the neritic zones of the North and South American continents, including adjacent islands and coral reefs. The focus is on species from subtropical and tropical waters, primarily within the genera Prorocentrum, Gambierdiscus/Fukuyoa, Coolia, Ostreopsis and Amphidinium. The state of knowledge on reported taxa in these waters is inadequate and time-series data are generally lacking for the prediction of regime shift and global change effects. Details of their respective toxigenicity and toxin composition have only recently been explored in a few locations. Nevertheless, by describing the specific ecosystem habitats for toxigenic benthic dinoflagellates, and by comparing those among the three key regions - the Gulf of Mexico, Caribbean Sea and the subtropical and tropical Pacific coast, insights for further risk assessment of the global spreading of toxic benthic species is generated for the management of their effects in Latin America.

The morphology and molecular phylogenetic relationships of Coolia species isolated from Brazil, including C. malayensis, C. tropicalis and a new lineage of the Coolia canariensis complex, are presented. Morphology was investigated by light and scanning electron microscopy. No significant morphological differences between the Brazilian strains and other geographically distant strains of C. malayensis and C. tropicalis were observed. In LSU and ITS rDNA phylogenies C. malayensis and C. tropicalis sequences from Brazil branched within the clade of these species with strains isolated from elsewhere. Phylogenetic relationships (LSU rDNA) within the C. canariensis species complex support the existence of three cryptic species. No morphological difference was discernible among species in this complex. Additional molecular, morphological and toxin data from globally distributed isolates should be acquired to strengthen our knowledge of the C. canariensis species complex. [ABSTRACT FROM AUTHOR]

Data on the first recorded marine alga Prorocentrum leve Faust, Vandersea, Kibler, Tester & Litaker (Dinophyceae) in a Russian inland waterbody, the hypersaline Lake Manych-Gudilo, are given. As a result, in May, July, and October 2016 and February 2017 it was revealed that the species was found in small quantities, mainly in the northwestern part of the lake. Its morphology, studied with an electron scanning microscope, is largely consistent with that described in the literature. The presence of marine species P. leve can serve as indirect evidence of the fragmentation of marine algal areas as a result of paleobasin regression. The results expand information on the composition of the algal flora of inland water bodies in Russia, as well as on the environmental opportunities and general distribution of P. leve. [ABSTRACT FROM AUTHOR]

A new thecate, photosynthetic, sand‐dwelling marine dinoflagellate, Laciniporus arabicus gen. et sp. nov., is described from the subtidal sediments of the Omani coast in the Arabian Sea, northern Indian Ocean, based on detailed morphological and molecular data. Cells of L. arabicus are small (16.2–30.1 μm long and 13.1–23.2 μm wide), dorsoventrally compressed, with a small apical flap‐shaped projection pointing to the left. The thecal plate pattern is distinguished by minute first precingular plate and sulcus, which extends into the epitheca, with large anterior and right sulcal plates. The Kofoidian thecal tabulation is Po, X, 4′, 2a, 7′′, 6c, 6s, 5′′′, 2′′′′. Morphologically, the revealed plate pattern has an affinity to the Peridiniales, and LSU rDNA based phylogenetic analyses placed L. arabicus within the Thoracosphaeraceae, close to calcareous‐cyst producing scrippsielloids, predatory pfiesteriaceans, and photosynthetic freshwater peridinioids Chimonodinium lomnickii and Apocalathium spp. However, the thecal plate arrangement of L. arabicus differs noticeably from any currently described dinoflagellates, and the species stands out from closely related taxa by extensive differences in physiology and ecology. [ABSTRACT FROM AUTHOR]

A new thecate, photosynthetic, sand‐dwelling marine dinoflagellate, Laciniporus arabicus gen. et sp. nov., is described from the subtidal sediments of the Omani coast in the Arabian Sea, northern Indian Ocean, based on detailed morphological and molecular data. Cells of L. arabicus are small (16.2–30.1 μm long and 13.1–23.2 μm wide), dorsoventrally compressed, with a small apical flap‐shaped projection pointing to the left. The thecal plate pattern is distinguished by minute first precingular plate and sulcus, which extends into the epitheca, with large anterior and right sulcal plates. The Kofoidian thecal tabulation is Po, X, 4′, 2a, 7′′, 6c, 6s, 5′′′, 2′′′′. Morphologically, the revealed plate pattern has an affinity to the Peridiniales, and LSU rDNA based phylogenetic analyses placed L. arabicus within the Thoracosphaeraceae, close to calcareous‐cyst producing scrippsielloids, predatory pfiesteriaceans, and photosynthetic freshwater peridinioids Chimonodinium lomnickii and Apocalathium spp. However, the thecal plate arrangement of L. arabicus differs noticeably from any currently described dinoflagellates, and the species stands out from closely related taxa by extensive differences in physiology and ecology. [ABSTRACT FROM AUTHOR]

Highlights • Temperature and nutrient conditions affected growth and toxin production. • Production of okadaic acid (OA) was induced in all conditions in Prorocentrum hoffmannianum. • Toxin production was enhanced in P-limited conditions at 27 °C. • OA concentrations were 1 order of magnitude higher than in other DSP species. • No OA esters were detected in this strain of Prorocentrum hoffmannianum. Abstract The benthic dinoflagellate Prorocentrum hoffmannianum M.A. Faust is typical of tropical warm waters and produces biotoxins responsible for diarrhetic shellfish poisoning (DSP). In this study, the effect of temperature and nutrient limitation on growth and toxin production of P. hoffmannianum isolated from field samples collected in the Florida Keys was investigated. Batch culture experiments were ran at two temperatures (i.e. 21 ± 0.1 and 27 ± 0.1 °C) and under nitrogen-limited (14.7 μmol L−1 N-NO 3 - and 18.1 μmol L−1 P-PO 4 3-) and phosphorus-limited (441 μmol L−1 N-NO 3 - and 0.6 μmol L−1 P-PO 4 3-) levels with respect to control nutrient conditions (441 μmol L−1 N-NO 3 -and 18.1 μmol L−1 P-PO 4 3-). Both temperature and nutrient conditions significantly affected growth rates and maximum yield of P. hoffmannianum with the maximum values being recorded at the higher temperature and in the replete medium. Production of okadaic acid was induced under all conditions (from 13.5 to 859.8 pg cell−1), with values up to one order of magnitude higher than those observed in other DSP toxin producing species. Toxin production was enhanced under P limitation at 27 °C, corroborating the theory that toxin production is modulated by cell physiological conditions, which are in turn affected by a wide spectrum of factors, including environmental stressors such as nutrient availability. Toxin fraction released in the growth medium was negligible. No okadaic acid esters were detected in this strain of P. hoffmannianum. [ABSTRACT FROM AUTHOR]

Highlights • Ecology and proliferation dynamics of O. cf. ovata are driven by complex interactions. • Higher abundances of O. cf. ovata observed in sheltered zones. • The dominant macroalgal community has a significant effect on bloom dynamics. • Urbanised sites are more prone to the proliferation of toxic benthic microalgae. • Larger risk exposure to toxic effects for humans in urban and sheltered areas. Abstract In the last few decades, Ostreopsis spp., toxic benthic dinolagellates of tropical origin, generated large interest in the Mediterranean Sea, where several bloom events have been observed. Ecology and proliferation dynamics of O. cf. ovata are driven by complex interactions among biotic and abiotic drivers, and understanding mechanisms triggering bloom events is still far from being complete. The aim of the present study is to highlight the role of different habitat conditions, elucidating the effects of i) exposure to hydrodynamic conditions, ii) macroalgal community and iii) urbanisation level, in driving O. cf. ovata bloom dynamics. A significant effect of hydrodynamics was observed only for cells in seawater, with higher abundances in sheltered zones, irrespective of the urbanisation level. Similarly, a significant effect of the dominant macroalgal community, with higher abundances in Corallinales and turf dominated communities, and lower ones in Cystoseira amentacea canopies, has been recorded, consistently in the differently urbanised sites. Additionally, stretches of the coast suffering from a more intense anthropic exploitation are in general more prone to the proliferation of potentially toxic benthic microalgae. All these results imply a larger risk exposure to toxic effects for humans in urban beaches and sheltered areas, usually more attended by swimmers and bathers. These findings underline the need to preserve, and eventually restore, canopy dominated assemblages, which presently are under regression because of human threats, providing a straightforward example that restoration of relevant habitats implies a cascading improvement of human welfare. [ABSTRACT FROM AUTHOR]

Dinoflagellates from Red Sea are hardly studied, in particular the benthic forms. Samples collected from shallow intertidal zone, Ain Sokhna, Egypt were microscopically examined. Three genera with seven species were recorded. The most frequently-encountered was Katodinium sp., a small mushroom-like with epitheca being consistently larger than hypotheca. Light micrographs revealed the presence of a nucleus in the hyposome and descending cingulum. Scanning electromicrographs (SEM) confirmed this orientation and revealed the presence of apical pore system. Another species showed similarity to the mushroom-like morphology but with large conical episome and small hyposome. Heterotrophic, naked Gyrodinium cf dominans and Gyrodinium sp. were also observed where in the former, there were conspicuous longitudinal striations. A frequently-observed species had naked Gyrodinium-like morphology but with much smaller size. One photosynthetic species had a characteristic stigma similar to type B eyespot in “dinotoms” and episome being slightly larger than hyposome. Gymnodinium sp. with sulcus extending slightly in the episome but deeply to the end of hyposome was also recorded. This genus is reported to be mostly toxic and its presence should be monitored. Finally, this study presents some early records for benthic dinophytes from rather underexplored locality and raises alerts about genus with reported toxicity.

The relationship between the ciguatoxin-producer benthic dinoflagellate Gambierdiscus and other epibenthic dinoflagellates in the Canary Islands was examined in macrophyte samples obtained from two locations of Fuerteventura Island in September 2016. The genera examined included Coolia, Gambierdiscus, Ostreopsis, Prorocentrum, Scrippsiella, Sinophysis, and Vulcanodinium. Distinct assemblages among these benthic dinoflagellates and preferential macroalgal communities were observed. Vulcanodinium showed the highest cell concentrations (81.6 × 103 cells gr−1 wet weight macrophyte), followed by Ostreopsis (25.2 × 103 cells gr−1 wet weight macrophyte). These two species were most represented at a station (Playitas) characterized by turfy Rhodophytes. In turn, Gambierdiscus (3.8 × 103 cells gr−1 wet weight macrophyte) and Sinophysis (2.6 × 103 cells gr−1 wet weight macrophyte) were mostly found in a second station (Cotillo) dominated by Rhodophytes and Phaeophytes. The influence of macrophyte’s thallus architecture on the abundance of dinoflagellates was observed. Filamentous morphotypes followed by macroalgae arranged in entangled clumps presented more richness of epiphytic dinoflagellates. Morphometric analysis was applied to Gambierdiscus specimens. By large, G. excentricus was the most abundant species and G. australes occupied the second place. The toxigenic potential of some of the genera/species distributed in the benthic habitats of the Canary coasts, together with the already known presence of ciguatera in the region, merits future studies on possible transmission of their toxins in the marine food chain.

Recurrent blooms of Ostreopsis cf. ovata have been reported in Brazil and the Mediterranean Sea with associated ecological, and in the latter case, health impacts. Molecular data based on the D1−D3 and D8−D10 regions of the LSU rDNA and ITS loci, and the morphology of O. cf. ovata isolates and field populations from locations along the Brazilian tropical and subtropical coastal regions and three oceanic islands are presented. Additional ITS sequences from three single cells from the tropical coast are provided. Toxin profiles and quantities of PLTX and their analogues; OVTXs; contained in cells from two clonal cultures and two field blooms from Rio de Janeiro were investigated. Morphology was examined using both light and epifluorescence microscopy. Morphometric analysis of different strains and field populations from diverse locations were compared. Molecular analysis showed that six of the seven sequences grouped at the large “Atlantic/Mediterranean/Pacific” sub-clade, while one sequence branched in a sister clade with sequences from Madeira Island and Greece. The toxin profile of strains and bloom field samples from Rio de Janeiro were dominated by OVTX-a and -b, with total cell quotas (31.3 and 39.3 pg cell−1) in the range of that previously reported for strains of O. cf. ovata.

Highlights • Morphological, molecular and toxinological analyses were performed on three strains of the benthic dinoflagellate Prorocentrum hoffmannianum from Canary Islands. • Morphological observations (SEM) corresponded with P. maculosum and the taxonomy of this species was revised and proposed as a junior synonym of P. hoffmannianum whose description is emended. • LC-HRMS analyses on cell extracts detected okadaic acid and three analogs in all strains. Abstract Three strains of the toxic benthic dinoflagellate Prorocentrum hoffmannianum were isolated in the Canary Islands (north-east Atlantic Ocean, Spain). The identity of the strains was determined by phylogenetic analyses of partial LSU rDNA (D1-D2 regions) but their morphology based on SEM images corresponded to P. maculosum. Their toxin profiles were analyzed by liquid chromatography and high resolution mass spectrometry analysis (LC–HRMS) on cell extracts and culture media. Okadaic acid and three analogs were detected in all strains. Rather, in culture media the detected compounds were variable among strains, two of them being okadaic acid analogs not found on cell extracts. As a result, the taxonomy of the species was revised and P. maculosum is proposed as a junior synonym of P. hoffmannianum whose description is emended. [ABSTRACT FROM AUTHOR]

The sand-dwelling dinoflagellate genera Adenoides and Pseudadenoides are morphologically very close but distinct in their molecular phylogeny. We established three cultures by isolating single cells from sand samples collected in intertidal zones of Qingdao (Yellow Sea), Dongshan (South China Sea) and Brittany (English Channel, North Atlantic, France). Strain morphology was examined with light and scanning electron microscopy, and both large subunit ribosomal DNA (LSU rDNA) and small subunit ribosomal DNA (SSU rDNA) sequences were amplified. Molecular phylogeny, corroborated by morphological examination showing the existence of a ventral pore, confirmed the identification of the French strain (RCC1982) as Adenoides eludens. The Chinese strains differed from Adenoides eludens in two additional posterior intercalary plates and differed from Pseudadenoides in one additional apical plate having the plate formula of Po, Cp, X, 5', 6'', 4S, 5''', 5p, 1'''' or alternatively Po, Cp, X, 5', 6'', 5S, 5''', 3p, 2''''. Maximum likelihood and Bayesian inference, carried out with concatenated LSU and SSU sequences, demonstrated that the Chinese strains were closely related but different from A. eludens and, in corroboration with morphological evidence, supported their classification as a distinct species, Adenoides sinensis sp. nov. Morphological and molecular results confirmed the close relationship between the two genera Adenoides and Pseudadenoides. [ABSTRACT FROM AUTHOR]

A new species of toxic benthic dinoflagellate is described based on laboratory cultures isolated from two locations from Brazil, Rio de Janeiro and Bahia. The morphology was studied with SEM and LM. Cells are elliptical in right thecal view and flat. They are 37–44 μm long and 29–36 μm wide. The right thecal plate has a V shaped indentation where six platelets can be identified. The thecal surface of both thecal plates is smooth and has round or kidney shaped and uniformly distributed pores except in the central area of the cell, and a line of marginal pores. Some cells present an elongated depression on the central area of the apical part of the right thecal plate. Prorocentrum caipirignum is similar to Prorocentrum lima in its morphology, but can be differentiated by the general cell shape, being elliptical while P. lima is ovoid. In the phylogenetic trees based on ITS and LSU rDNA sequences, the P. caipirignum clade appears close to the clades of P. lima and Prorocentrum hoffmannianum. The Brazilian strains of P. caipirignum formed a clade with strains from Cuba, Hainan Island and Malaysia and it is therefore likely that this new species has a broad tropical distribution. Prorocentrum caipirignum is a toxic species that produces okadaic acid and the fast acting toxin prorocentrolide. [ABSTRACT FROM AUTHOR]

• Reports of BHAB species and related harmful events in South America (SA) were reviewed. • Greater diversity of toxigenic species found in equatorial/tropical areas of the continent. • Prorocentrum lima complex is the most frequent and widespread BHAB taxon in SA. • Ciguatera events reported in Colombia and Venezuela since the 1970s and 80s. • Enhanced analytical capacity and BHAB monitoring are necessary in most parts of SA. Public awareness about Benthic Harmful Algal Blooms (BHABs) and their negative impacts has increased substantially over the past few decades. Even so, reports of BHABs remain relatively scarce in South America (SA). This paper provides a comprehensive overview of the current state of knowledge on BHABs in the continent, by integrating data from published articles, books, and technical reports. We recorded ∼300 different occurrences of potentially toxic BHAB species over the Caribbean, Atlantic and Pacific coasts, mostly in marine (>95%) but also in estuarine areas located from 12⁰36′ N to 54⁰53′ S. Over 70% of the data was published/released within the past 10 years, and ∼85% were concentrated in Brazil, Venezuela, Ecuador and Colombia. Benthic species were mainly associated with macroalgae, seagrass and sediment. Incidental detection in the plankton was also relevant, mainly in places where studies targeting BHAB species are still rare, like Argentina, Uruguay, Chile and Peru. The study listed 31 infrageneric taxa of potentially toxic benthic dinoflagellates and eight of estuarine cyanobacteria occurring in SA, with the greatest species diversity recorded in the equatorial-tropical zone, mainly in northeastern Brazil (Atlantic), Venezuela and Colombia (Caribbean), and the Galapagos Islands, Ecuador (Pacific). Local strains of Amphidinium, Gambierdiscus, Coolia and Prorocentrum spp. produced toxic compounds of emerging concern. Prorocentrum lima species complex was the most common and widely distributed taxon, followed by Ostreopsis cf. ovata. In fact, these two dinoflagellates were associated with most BHAB events in SA. Whereas the former has caused the contamination of multiple marine organisms and cases of Diarrhetic Shellfish Poisoning in subtropical and temperate areas, the latter has been associated with faunal mortalities and is suspected of causing respiratory illness to beach users in tropical places. Ciguatera Poisoning has been reported in Colombia (∼240 cases; no deaths) and Venezuela (60 cases; two deaths), and may be also a risk in other places where Gambierdiscus spp. and Fukuyoa paulensis have been reported, such as the Galapagos Islands and the tropical Brazilian coast. Despite the recent advances, negative impacts from BHABs in SA are intensified by limited research/training funding, as well as the lack of official HAB monitoring and poor analytical capability for species identification and toxin detection in parts of the continent. [ABSTRACT FROM AUTHOR]

Variations in toxicity of the benthic dinoflagellate Ostreopsis Schmidt 1901 have been attributed to specific molecular clades, biogeography of isolated strains, and the associated bacterial community. Here, we attempted to better understand the biodiversity and the basic biology influencing toxin production of Ostreopsis. Nine clonal cultures were established from Okinawa, Japan, and identified using phylogenetic analysis of the ITS-5.8S rRNA and 28S rRNA genes. Morphological analysis suggests that the apical pore complex L/W ratio could be a feature for differentiating Ostreopsis sp. 2 from the O. ovata species complex. We analyzed the toxicity and bacterial communities using liquid chromatography-mass spectrometry, and PCR-free metagenomic sequencing. Ovatoxin was detected in three of the seven strains of O. cf. ovata extracts , highlighting intraspecies variation in toxin production. Additionally, two new potential analogs of ovatoxin-a and ostreocin-A were identified. Commonly associated bacteria clades of Ostreopsis were identified from the established cultures. While some of these bacteria groups may be common to Ostreopsis (Rhodobacterales, Flavobacteria-Sphingobacteria, and Enterobacterales) , it was not clear from our analysis if any one or more of these plays a role in toxin biosynthesis. Further examination of biosynthetic pathways in metagenomic data and additional experiments isolating specific bacteria from Ostreopsis would aid these efforts. [ABSTRACT FROM AUTHOR]

The distribution and abundance of epiphytic and planktonic Coolia monotis Meunier along the Alexandria coast were studied through five annual cycles; from summer 2005 to summer 2010 at four sites: Abu Qir Beach, Stanly, Eastern Harbour and Mex Beach. The morphology of C. monotis was characterised by noticeable small size specimens in the E.H., the D.V. diameter is not exceeding 20 μm and width between 10 and 15 μm. On the other hand, the epiphytic specimens showed a normal cell size. The species was most abundant as planktonic form in the E.H., reaching 15.2 × 103 cell l−1 during summer 2010. The epiphytic forms showed lower density, with a maximum of 454 cell g−1 fwm during autumn 2005, 2006 and summer from 2007 to 2010. The fluctuations of cell abundance of C. monotis showed a significant negative correlation with salinity and a weak positive correlation with temperature. This study represents the first report of Coolia monotis Meunier in the Egyptian Mediterranean waters.

Approximately 70 species of Prorocentrum are known, of which around 30 species are associated with benthic habitats. Some produce okadaic acid (OA), dinophysistoxin (DTX) and their derivatives, which are involved in diarrhetic shellfish poisoning. In this study, we isolated and characterized Prorocentrum concavum and P. malayense from Broome in north Western Australia using light and scanning electron microscopy as well as molecular sequences of large subunit regions of ribosomal DNA, marking the first record of these species from Australian waters. The morphology of the motile cells of P. malayense was similar to P. concavum in the light microscopy, but differed by the smooth thecal surface, the pore pattern and the production of mucous stalk-like structures and a hyaline sheath around the non-motile cells. P. malayense could also be differentiated from other closely related species, P. leve and P. foraminosum, despite the similarity in thecal surface and pore pattern, by its platelet formula and morphologies. We tested the production of OA and DTXs from both species, but found that they did not produce detectable levels of these toxins in the given culturing conditions. This study aids in establishing more effective monitoring of potential harmful algal taxa in Australian waters for aquaculture and recreational purposes.

Dinoflagellates belonging to the genus Gambierdiscus produce ciguatoxins (CTXs), which are metabolized in fish to more toxic forms and subsequently cause ciguatera fish poisoning (CFP) in humans. Five species of Gambierdiscus have been described from the Canary Islands, where CTXs in fish have been reported since 2004. Here we present new data on the distribution of Gambierdiscus species in the Canary archipelago and specifically from two islands, La Palma and La Gomera, where the genus had not been previously reported. Gambierdiscus spp. concentrations were low, with maxima of 88 and 29 cells·g−1 wet weight in samples from La Gomera and La Palma, respectively. Molecular analysis (LSUrRNA gene sequences) revealed differences in the species distribution between the two islands: only G. excentricus was detected at La Palma whereas four species, G. australes, G. caribaeus, G. carolinianus, and G. excentricus, were identified from La Gomera. Morphometric analyses of cultured cells of the five Canary Islands species and of field specimens from La Gomera included cell size and a characterization of three thecal arrangement traits: (1) the shape of the 2′ plate, (2) the position of Po in the anterior suture of the 2′ plate, and (3) the length−width relationship of the 2″″ plate. Despite the wide morphological variability within the culture and field samples, the use of two or more variables allowed the discrimination of two species in the La Gomera samples: G. cf. excentricus and G. cf. silvae. A comparison of the molecular data with the morphologically based classification demonstrated important coincidences, such as the dominance of G. excentricus, but also differences in the species composition of Gambierdiscus, as G. caribaeus was detected in the study area only by using molecular methods.

A study on the presence of benthic dinoflagellates in the intertidal zone along the coasts of Jeju Island, Korea was conducted during 2011 and 2012. Identification and taxonomic observations were made of the benthic dinoflagellate samples using light and epifluorescence microscopy. Thirty-seven dinoflagellate taxa belong to five orders, nine families, 18 genera and 30 species, which are new records for Korean waters, were detected in this study. The detailed nomenclature, references, distribution, and illustrations are presented here. The commonly occurring genera were Amphidinium, Coolia, Ostreopsis, Prorocentrum, and Thecadinium. Among the recorded species, 26 were found only in sand sediment, seven in macroalgal samples, and four were found in both sand and macroalgal samples. Of the 37 species, nine were potentially toxic. These results suggest that diversified benthic dinoflagellates including several potentially toxic species occur in sand sediment and macroalgae in the intertidal zone along the coasts of Jeju Island. The morphological features of the identified species were more or less similar to observations made by previous studies in Korea and elsewhere. The presence of known toxic species may indicate a potential risk of toxicity in the marine ecosystem of Jeju Island. The present study can be helpful for further detailed taxonomic, toxicological, molecular phylogenetic studies and may help in the management and conservation of Jeju Island's marine ecosystem.

Ostreopsis blooms regularly occur in many Mediterranean coastal areas in late summer-autumn. In the northern Adriatic Sea, Ostreopsis blooms affect diatom-dominated microphytobenthic communities. In this study, the effects of the filtrates of some diatom species, both benthic ( Tabularia affinis , Proschkinia complanatoides and Navicula sp.) and planktonic ( Thalassiosira sp. and Skeletonema marinoi ) on cell morphology, cytological features and growth of O . cf. ovata were investigated. Our results showed a marked decrease of O . cf. ovata growth when cells were exposed to all diatom filtrates tested. The highest inhibitions were observed for exposures to P. complanatoides and Navicula sp. filtrates (92.5% and 80%, respectively) and increased with the age of diatom culture. Moreover, a clear DNA degradation and abnormal forms of O. cf. ovata cells (83.8% of the total) were found at the highest concentrations using Navicula sp. filtrate after 10 days of the inoculum. [ABSTRACT FROM AUTHOR]

Concern regarding Benthic Harmful Algal Blooms (BHABs) is increasing since some harmful benthic species have been identified in new areas. In the Mediterranean basin, the most common harmful benthic microalgae are Ostreopsis cf. ovata and Prorocentrum lima, which produce palytoxin-like compounds and okadaic acid respectively, and the need to implement monitoring activities has increased. However, a general agreement on appropriate strategies (e.g. sampling season, definition of alarm thresholds, etc.) is still lagging behind, especially for P. lima, whose proliferation dynamics are still poorly known. [ABSTRACT FROM AUTHOR]

A microcosm designed for culturing aquatic phototrophic biofilms on artificial substrata was used to perform experiments with microphytobenthos sampled during summer toxic outbreaks of Ostreopsis cf. ovata along the Middle Tyrrhenian coast. This dynamic approach aimed at exploring the unique and complex nature of O. cf. ovata bloom development in the benthic system. Epibenthic assemblages were used as inocula for co-cultures of bloom organisms on polycarbonate slides at controlled environmental conditions. Biofilm surface adhesion, growth, and spatial structure were evaluated along with shifts in composition and matrix production in a low disturbance regime, simulating source habitat. Initial adhesion and substratum colonisation appeared as stochastic processes, then community structure and physiognomy markedly changed with time. Dominance of filamentous cyanobacteria and diatoms, and dense clusters of Amphidinium cf. carterae at the mature biofilm phases, were recorded by light and confocal microscopy, whilst O. cf. ovata growth was visibly limited in the late culture phases. Life-form strategies, competitiveness for resources, and possibly allelopathic interactions shaped biofilm structure during culture growth. HPLC (High Performance Liquid Chromatography) analysis of exopolysaccharidic matrix revealed variations in sugar total amounts and composition. No toxic compounds were detected in the final communities tested by LC-MS (Liquid Chromatography- Mass Spectrometry) and MALDI-TOF MS (Matrix Assisted Laser Desorption Ionization Time OF Flight Mass Spectroscopy) techniques. [ABSTRACT FROM AUTHOR]

Ciguatera Fish Poisoning (CFP) is increasing across the Pacific and the distribution of the causative dinoflagellates appears to be expanding. Subtle differences in thecal plate morphology are used to distinguish dinoflagellate species, which are difficult to determine using light microscopy. For these reasons we sought to develop a Quantitative PCR assay that would detect all species from both Gambierdiscus and Fukuyoa genera in order to rapidly screen environmental samples for potentially toxic species. Additionally, a specific assay for F. paulensis was developed as this species is of concern in New Zealand coastal waters. Using the assays we analyzed 31 samples from three locations around New Zealand and the Kingdom of Tonga. Fourteen samples in total were positive for Gambierdiscus/Fukuyoa and two samples were also positive using the F. paulensis assay. Samples from the Kermadec Islands were further characterized using high-throughput sequencing metabarcoding. The majority of reads corresponded to Gambierdiscus species with three species identified at all sites (G. australes, G. honu and G. polynesiensis). This is the first confirmed identification of G. polynesiensis, a known ciguatoxin producer, in New Zealand waters. Other known toxin-producing genera were also detected, included Alexandrium, Amphidinium, Azadinium, Dinophysis, Ostreopsis, and Prorocentrum. [ABSTRACT FROM AUTHOR]

In the present study the geographical distribution, abundance and composition of Gambierdiscus was described over a 600 km longitudinal scale in the Canary Islands. Samples for cell counts, isolation and identification of Gambierdiscus were obtained from five islands (El Hierro, Tenerife, Gran Canaria, Fuerteventura and Lanzarote). Average densities of Gambierdiscus spp. between 0 and 2200 cells g −1 blot dry weight of macrophyte were recorded. Morphological (light microscopy and SEM techniques) and molecular analyses (LSU and SSU rDNA sequencing of cultures and single cells from the field) of Gambierdiscus was performed. Five Gambierdiscus species ( G. australes, G. caribaeus, G. carolinianus, G. excentricus and G. silvae ), together with a new putative species ( Gambierdiscus ribotype 3) were identified. These results suggest that some cases of CFP in the region could be associated with the accumulation of ciguatoxins in the marine food web acquired from local populations of Gambierdiscus . This unexpected high diversity of Gambierdiscus species in an area which a priori is not under risk of ciguatera, hints at an ancient settlement of Gambierdiscus populations, likely favored by warmer climate conditions in the Miocene Epoch (when oldest current Canary Islands were created), in contrast with cooler present ones. Currently, warming trends associated with climate change could contribute to extend favorable environmental conditions in the area for Gambierdiscus growth especially during winter months. [ABSTRACT FROM AUTHOR]

The morphology of the potentially toxic dinoflagellate Prorocentrum foraminosum was examined in detail using light and scanning electron microscopy for the first time for the seas of Russia. New morphological features of this species were found and documented. Long-term observations showed that P. foraminosum occurred regularly from April to November in the epiphytic assemblages of Peter the Great Bay. The highest cell abundance was recorded in June (1.5 × 10 cells/g macrophyte dry weight). This dinoflagellate was also found rarely at a low cell densities in coastal sands. [ABSTRACT FROM AUTHOR]

Despite the potential negative human health, ecological and economic impact, the ecology of harmful benthic dinoflagellate blooms remains largely unknown. This is probably due to the complex interactions among biotic and abiotic drivers that influence blooms, but also to the difficulty in quantifying cell abundance in a comparable way over large spatial and temporal scales. One of the recognized priorities for bHABs (benthic Harmful Algal Blooms) assessment is developing and standardizing methods that can provide comparable data. In this context, the Benthic Dinoflagellates Integrator (BEDI), a new non-destructive quantification method for benthic dinoflagellate abundances, has been developed and tested within the present study. The rationale behind the BEDI standard assessment method is that mechanical resuspension of cells enables the quantification of abundances as cells per unit of seabed surface area (i.e. cells mm −2 ) or as Potentially Resuspended cells per unit of volume (PRcells ml −1 ), by integrating both cells in the biofilm and those in the surrounding water. Estimations of Ostreopsis performed with BEDI method are independent of the substratum (i.e. macroalgal species) or the dominant ecosystem (i.e. algal forests or turfs, seagrass beds, coral reefs) and potentially allow the comparison of benthic dinoflagellate blooms over broad temporal and spatial scales. The first application of the BEDI method, presented in this study, gave encouraging results: the characterization of blooms of Ostreopsis cf. ovata at three sites in the NW Mediterranean Sea is consistent with results derived from the other commonly applied methods. Quantification of the ratio between abundances of cells in the biofilm and in the surrounding water was calculated for the first time per unit of seabed surface area, demonstrating that the highest abundances of cells (the stock), and therefore the associated risk for human health, are in the biofilm. For risk assessment purposes, conversion values for commonly used monitoring alert thresholds of Mediterranean Ostreopsis blooms are provided. [ABSTRACT FROM AUTHOR]

A new marine benthic dinoflagellate, Testudodinium magnum sp. nov., was described from a sand sample collected on the seafloor at a depth of 35 m off Mageshima Island, Kagoshima, Japan. The dinoflagellate possessed the characteristic features of the genus Testudodinium, but was distinguished by its extremely large size and pebbled dorsal surface of the hyposome, caused by the presence of numerous nodules. The cells of this dinoflagellate possessed a dominant sessile and a rare motile form that were morphologically distinct from each other: The sessile form was larger and the small rounded episome with longitudinal furrow was completely embedded in the hyposome; the motile form was smaller and the episome was only partly embedded in the hyposome. The ultrastructural investigations revealed the presence of a large, circular, starch-sheathed pyrenoid whose matrix was traversed by randomly arranged thylakoid lamellae. The chloroplasts formed a network radiating outward from the pyrenoid. Uniquely, this dinoflagellate possessed internal props - structures that spanned the thickness of the cell and were fibrous in nature. The props were numerous and passed through organelles and cell contents. Phylogenetic analyses based on the small-subunit ribosomal DNA gene sequences placed this dinoflagellate firmly within the Testudodinium clade with high support. On the basis of the morphological features and phylogenetic analyses, we concluded that this dinoflagellate was a new species in the genus Testudodinium. [ABSTRACT FROM AUTHOR]

The aim of this study was to describe the morphology of species of the benthic dinoflagellate genus Sinophysis from the tropical South Atlantic. Species were collected from four sampling sites and were identified based on light and epifluorescence microscopy. Sinophysis microcephala was found at three sites. Cells were elongated and oval in lateral view. Sinophysis canaliculata was recorded at two sites. Cells were round in lateral view and a short cut was present at the H2 plate. To the best of our knowledge, this is the first record of the genus Sinophysis from the South Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Three new thecate, heterotrophic sand-dwelling marine dinoflagellates of the genus Amphidiniopsis were collected in sublittoral sand of Peter the Great Bay of the Sea of Japan. The cell morphology was examined by light and scanning electron microscopy. All three species were dorsoventrally flattened and had three anterior intercalary plates. Amphidiniopsis ovalis sp. nov. was oval, 27.0-43.5 μm long and 24.0-38.1 μm wide. The length to width ratio was 1.1-1.2. The plate formula was apical pore complex (APC) 4′ 3a 7″ 3c 4(5)s 5′″ 2″″. The first apical plate was not in contact with the APC. The cingulum was slightly ascending less than half a cingular width. The sulcus was characteristically curved and slightly shifted to the left side of the cell. The theca was smooth or slightly reticulated. Amphidiniopsis elongata sp. nov. was almost rectangular, with a small apical hook and rounded posterior end, 42.0-64.0 μm long and 28.0-42.0 μm wide. The length to width ratio was 1.3-1.7. The cingulum was ascending about four cingular widths. The sulcus was characteristically curved and markedly shifted to the left cell side. The plate formula was APC 4′ 3a 6″ 5c 4(6)s 5′″ 2″″. The theca was smooth with large and small pores. Amphidiniopsis hoppenrathae sp. nov. was rounded with a small apical hook, 39.2-48.9 μm long and 35.4-42.8 μm wide. The length to width ratio was 1.1. The plate formula was APC 4′ 3a 6″ 3c 4s 5′″ 2″. The first apical plate was not in contact with the sulcus, and three anterior intercalary plates were located on the ventral side. The cingulum ascended about two cingular widths. The sulcus was located in the middle of the ventral side of the cell. The theca was ornamented with short spines. [ABSTRACT FROM AUTHOR]

Cryptic and pseudo-cryptic species are common amongst marine phytoplankton, and may cause misleading inferences of ecological and physiological data of plankton community studies. Deciphering the diversity and distribution of species of the benthic dinoflagellate Ostreopsis is one example, as there are many morphologically indistinct clades that differ greatly genetically and toxicologically from one another. In this study, a new species, Ostreopsis rhodesae from the southern Great Barrier Reef was described. While it initially appeared to be highly similar to several other Ostreopsis species, we found O. rhodesae can be distinguished based on the relative size of the second apical plate (2′), which is twice as long as the APC plate, and separates the third apical (3′) from the third precingular (3′′) plate. Phylogenetic trees based on the SSU, ITS/5.8S and D1-D2 and D8-D10 regions of the LSU rRNA were well supported, and showed a clear difference to other Ostreopsis clades. Compensatory base changes (CBCs) were identified in helices of the ITS2 between O. rhodesae and O . cf. ovata and O . cf. siamensis , which were also present in the same habitat. Fish gill cell lines were toxic to O. rhodesae , cell extracts but no palytoxin-like analogues were found in them. The findings highlight a case of pseudo-cryptic speciation, found in sympatry with closely related and morphologically similar species, but biologically and functionally distinct. [ABSTRACT FROM AUTHOR]