Ostreopsis cf. ovata in the Gulf of Gabès (south-eastern Mediterranean Sea): morphological,molecular and ecological characterization |
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| Institution: | 1. National Institute of Marine Sciences and Technologies, BP 1035, 3018 Sfax, Tunisie;2. National Institute of Marine Sciences and Technologies, Fishing Port, 2060 La Goulette, Tunisie;3. Environment Reference Laboratory, Portuguese Environment Agency, Rua da Murgueira, 9/9A | Zambujal, 2611-865 Amadora, Portugal;4. Department of Biomolecular Sciences, University of Urbino, 61121 Pesaro (PU), Italy;1. Cawthron Institute, 98 Halifax Street East, Private Bag 2, Nelson 7042, New Zealand;2. AgResearch, Ruakura Agricultural Research Centre, 10 Bisley Road, Private Bag 3240, Hamilton, New Zealand;1. Division of Clinical Toxicology and Occupational Medicine, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan;2. Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan;3. Institute of Environmental and Occupational Health Sciences, School of Medicine, National Yang-Ming University, Taipei, Taiwan;4. Taitung Hospital, Ministry of Health and Welfare, Taitung, Taiwan;1. Ifremer, BIODIVENV, F-97231 Le Robert, Martinique, France;2. Ifremer, LITTORAL, F-29900 Concarneau, France;3. Sorbonne Université, CNRS, Laboratoire d’Océanographie de Villefranche, Villefranche-sur-Mer, France;1. LAQUES (Laboratory of Aquatic Environmental Science), Faculty of Agriculture, Kochi University, Kochi 783-8502, Japan;2. The United Graduate School of Agricultural Sciences, Ehime University, Ehime 790-8566, Japan;3. Fukui Prefectural University, 1-1 Gakuen-cho, Obama City, Fukui 917-0003, Japan |
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| Abstract: | In the last few decades, the frequency of the toxic benthic dinoflagellate Ostreopsis cf. ovata proliferation has increased in the Mediterranean Sea. These blooms are associated with harmful effects on human health and the environment. The present work provides the first long term study on the spatio-temporal distribution of O. cf. ovata in relation to physical parameters in the Gulf of Gabès coastal waters (south-eastern Mediterranean Sea), as well as its morphological, molecular and physiological features. The strains of O. cf. ovata were identified morphologically by light and epifluorescence microscopy. The morphology and the size range of cultured strains were similar to those described regarding O. cf. ovata isolated from the Mediterranean Sea. The ultrastructural analysis of O. cf. ovata cells using the transmission electron microscopy showed the presence of numerous vesicles (VE) containing spirally coiled fibers (SCFs) connected to the mucus canal (CH). The phylogenetic tree based on the internal transcribed spacer region containing the 5.8S rDNA (ITS-5.8S rDNA) revealed that O. cf. ovata strains were placed into the Mediterranean/Atlantic clade. In addition, O. cf. ovata toxicity was evaluated by the mouse bioassay and a dose level ≥ 4 × 104 cells was found to be lethal to mice. The examination of the O. cf. ovata occurrence in the Gulf of Gabès at a large temporal scale (1997–2012) revealed a clear seasonal pattern with dominance from midsummer (July) to late autumn (November). Furthermore, a positive correlation was found between the abundance of O. cf. ovata and salinity, whereas no correlation was found as regards temperature. The occurrence of O. cf. ovata was only detected at salinity above 35 and the highest concentrations were observed at 45. Laboratory experiments confirmed such a result and showed that isolated O. cf. ovata strains had optimal growth at salinity ranging between 35 and 45, with its peak at 40. |
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| Keywords: | Morphology ITS-5 8S rDNA Distribution Mouse bioassay South-eastern Mediterranean sea |
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