Taxonomy and toxicity of a bloom-forming Ostreopsis species (Dinophyceae, Gonyaulacales) in Tahiti island (South Pacific Ocean): one step further towards resolving the identity of O. siamensis

•A benthic Ostreopsis bloom is described from tahiti Island, french polyensia.•Taxonomy and toxicity are analyzed from a bloom sample and 8 isolated strains.•The specimens belong to Ostreopsis sp. 6 and are morphologically close to O. siamensis.•Phylogenetic data reveal a close relationship with str...

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Bibliographic Details
Published in:Harmful algae 2020-09, Vol.98, p.101888, Article 101888
Main Authors: Chomérat, Nicolas, Bilien, Gwenael, Viallon, Jérôme, Hervé, Fabienne, Réveillon, Damien, Henry, Kévin, Zubia, Mayalen, Vieira, Christophe, Ung, André, Gatti, Clémence Mahana iti, Roué, Mélanie, Derrien, Amélie, Amzil, Zouher, Darius, Hélène Taiana, Chinain, Mireille
Format: Article
Language:English
Subjects:
Chromatography, Liquid
Dinoflagellate
Dinoflagellida - genetics
Environmental Sciences
Islands
ITS–5.8S rDNA
LSU rDNA
Malaysia
Microscopy
Morphology
Ostreocin
Pacific Ocean
Phylogeny
Polynesia
Tandem Mass Spectrometry
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Summary:•A benthic Ostreopsis bloom is described from tahiti Island, french polyensia.•Taxonomy and toxicity are analyzed from a bloom sample and 8 isolated strains.•The specimens belong to Ostreopsis sp. 6 and are morphologically close to O. siamensis.•Phylogenetic data reveal a close relationship with strains from the gulf of Thailand.•All the 8 strains studied are cytotoxic using CBA-N2a, and produce mostly OST-D. Among dinoflagellates responsible for benthic harmful algal blooms, the genus Ostreopsis primarily described from tropical areas has been increasingly reported from subtropical and temperate areas worldwide. Several species of this toxigenic genus produce analogs of palytoxin, thus representing a major threat to human and environmental health. The taxonomy of several species needs to be clarified as it was based mostly on morphological descriptions leading in some cases to ambiguous interpretations and misidentifications. The present study aims at reporting a benthic bloom that occurred in April 2019 in Tahiti island, French Polynesia. A complete taxonomic investigation of the blooming Ostreopsis species was realized using light, epifluorescence and field emission electron microscopy and phylogenetic analyses inferred from LSU rDNA and ITS–5.8S rDNA regions. Toxicity of a natural sample and strains isolated from the bloom was assessed using both neuroblastoma cell-based assay and LC-MS/MS analyses. Morphological observations showed that cells were round to oval, large, 58.0–82.5 µm deep (dorso-ventral length) and 45.7–61.2 µm wide. The cingulum was conspicuously undulated, forming a ‘V’ in ventral view. Thecal plates possessed large pores in depressions, with a collar rim. Detailed observation also revealed the presence of small thecal pores invisible in LM. Phylogenetic analyses were congruent and all sequences clustered within the genotype Ostreopsis sp. 6, in a subclade closely related to sequences from the Gulf of Thailand and Malaysia. No toxicity was found on the field sample but all the strains isolated from the bloom were found to be cytotoxic and produced ostreocin D, a lower amount of ostreocins A and B and putatively other compounds. Phylogenetic data demonstrate the presence of this species in the Gulf of Thailand, at the type locality of O. siamensis, and morphological data are congruent with the original description and support this identification.
ISSN:1568-9883
1878-1470
DOI:10.1016/j.hal.2020.101888