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Collos, Y., Jauzein, C., Laabir, M., & Vaquer, A. (2013). Discrepancies between net particulate carbon production and 13C-labelled bicarbonate uptake by Alexandrium catenella (Dinophyceae): grazing controls the balance between autotrophic and non autotrophic carbon acquisition1. Journal of Phycology, 49(3), 441–446.
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Collos, Y., Jauzein, C., Ratmaya, W., Souchu, P., Abadie, E., & Vaquer, A. (2014). Comparing diatom and Alexandrium catenella/tamarense blooms in Thau lagoon: Importance of dissolved organic nitrogen in seasonally N-limited systems. Harmful Algae, 37, 84–91.
Résumé: Diatom blooms in Thau lagoon are always related to rain events leading to inputs of inorganic nutrients such as phosphate, ammonium and nitrate through the watershed with time lags of about 1 week. In contrast, blooms of Alexandrium catenella/tamarense can occur following periods of 3 weeks without precipitation and no significant input of conventional nutrients such as nitrate and phosphate. Field results also indicate a significant drop (from 22–25 to 15–16 μM over 3 days) in dissolved organic nitrogen (DON) at the bloom peak, as well as a significant inverse relationship between A. catenella/tamarense cell density and DON concentrations that is not apparent for diatom blooms. Such dinoflagellate blooms are also associated with elevated (6–9 μM) ammonium concentrations, a curious feature also observed by other investigators, possibly the results of ammonium excretion by this organism during urea or other organic nitrogen assimilation. The potential use of DON by this organism represents short cuts in the nitrogen cycle between plants and nutrients and requires a new model for phytoplankton growth that is different from the classical diatom bloom model. In contrast to such diatom blooms that are due to conventional (nitrate, phosphate) nutrient pulses, Alexandrium catenella/tamarense blooms on the monthly time scale are due to organic nutrient enrichment, a feature that allows net growth rates of about 1.3 d−1, a value higher than that generally attributed to such organisms.
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Fertouna-Bellakhal, M., Dhib, A., Fathalli, A., Bellakhal, M., Chomérat, N., Masseret, E., et al. (2015). Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia, Southern Mediterranean Sea). Harmful Algae, 48, 69–82.
Résumé: Abstract
A high spatial resolution sampling of Alexandrium pacificum cysts, along with sediment characteristics (% H2O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotyping of cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum. The toxin profile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N-sulfocarbamoyl toxins C1 (9.82 pg toxin cell−1), the GTX6 (3.26 pg toxin cell−1) and the carbamoyl toxin Neo-STX (0.38 pg toxin cell−1). The latter represented only 2.8% of the total toxins in this strain. High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63 μm were examined as a favorable potential seedbed for initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.
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Genovesi, B., Berrebi, P., Nagai, S., Reynaud, N., Wang, J., & Masseret, E. (2015). Geographic structure evidenced in the toxic dinoflagellate Alexandrium pacificum Litaker (A. catenella – group IV (Whedon & Kofoid) Balech) along Japanese and Chinese coastal waters. Marine Pollution Bulletin, 98(1–2), 95–105.
Résumé: Abstract
The intra-specific diversity and genetic structure within the Alexandrium pacificum Litaker (A. catenella – Group IV) populations along the Temperate Asian coasts, were studied among individuals isolated from Japan to China. The UPGMA dendrogram and FCA revealed the existence of 3 clusters. Assignment analysis suggested the occurrence of gene flows between the Japanese Pacific coast (cluster-1) and the Chinese Zhejiang coast (cluster-2). Human transportations are suspected to explain the lack of genetic difference between several pairs of distant Japanese samples, hardly explained by a natural dispersal mechanism. The genetic isolation of the population established in the Sea of Japan (cluster-3) suggested the existence of a strong ecological and geographical barrier. Along the Pacific coasts, the South–North current allows limited exchanges between Chinese and Japanese populations. The relationships between Temperate Asian and Mediterranean individuals suggested different scenario of large-scale dispersal mechanisms.
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Hadjadji, I., Frehi, H., Ayada, L., Abadie, E., & Collos, Y. (2014). A comparative analysis of Alexandrium catenella/tamarense blooms in Annaba Bay (Algeria) and Thau lagoon (France); phosphorus limitation as a trigger. Comptes Rendus Biologies, 337(2), 117–122.
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