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Alexandrium catenella

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Mohamed Laabir – One of the best experts on this subject based on the ideXlab platform.

Yves Collos – One of the best experts on this subject based on the ideXlab platform.

Andre Vaquer – One of the best experts on this subject based on the ideXlab platform.

  • comparing diatom and Alexandrium catenella tamarense blooms in thau lagoon importance of dissolved organic nitrogen in seasonally n limited systems
    Harmful Algae, 2014
    Co-Authors: Yves Collos, Cecile Jauzein, Eric Abadie, Philippe Souchu, Widya Ratmaya, Andre Vaquer
    Abstract:

    Abstract 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.

  • Comparing diatom and Alexandrium catenella/tamarense blooms in Thau lagoon: Importance of dissolved organic nitrogen in seasonally N-limited systems
    Harmful Algae, 2014
    Co-Authors: Yves Collos, Cecile Jauzein, Eric Abadie, Philippe Souchu, Widya Ratmaya, Andre Vaquer
    Abstract:

    Abstract 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 orgaorganic nitrnitrogen (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 nitrnitrogen 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.

  • influences of sedimentation and hydrodynamics on the spatial distribution of Alexandrium catenella tamarense resting cysts in a shellfish farming lagoon impacted by toxic blooms
    Harmful Algae, 2013
    Co-Authors: Benjamin Genovesi, Andre Vaquer, Mohamed Laabir, David Mouillot, Thierry Laugier, Annie Fiandrino, Daniel Grzebyk
    Abstract:

    Abstract Since resting cysts are a potential seeding source for blooms, the presence of these cysts in sediments is a marker of an established population for a number of harmful algal species. The spatial patterns of cyst density in relation to sediment characteristics and hydrodynamics are still largely misunderstood. This study investigated the spatial distribution of resting cysts belonging to the Alexandrium tamarense species complex (Dinophyceae) in sediments of a Mediterranean coastal lagoon (Thau Lagoon, France). This lagoon, hosting shellfish farming, is regularly impacted by toxic Alexandrium catenella blooms. The average cyst density across the whole lagoon was rather low,

Daniel Grzebyk – One of the best experts on this subject based on the ideXlab platform.

Philippe Souchu – One of the best experts on this subject based on the ideXlab platform.

  • comparing diatom and Alexandrium catenella tamarense blooms in thau lagoon importance of dissolved organic nitrogen in seasonally n limited systems
    Harmful Algae, 2014
    Co-Authors: Yves Collos, Cecile Jauzein, Eric Abadie, Philippe Souchu, Widya Ratmaya, Andre Vaquer
    Abstract:

    Abstract 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.

  • Comparing diatom and Alexandrium catenella/tamarense blooms in Thau lagoon: Importance of dissolved organic nitrogen in seasonally N-limited systems
    Harmful Algae, 2014
    Co-Authors: Yves Collos, Cecile Jauzein, Eric Abadie, Philippe Souchu, Widya Ratmaya, Andre Vaquer
    Abstract:

    Abstract 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.

  • nitrogenous nutrition of Alexandrium catenella dinophyceae in cultures and in thau lagoon southern france
    Journal of Phycology, 2004
    Co-Authors: Yves Collos, Andre Vaquer, Mohamed Laabir, Celine Gagne, Philippe Cecchi, Philippe Souchu
    Abstract:

    Alexandrium catenella (Whedon et Kofoid) Balech was isolated from Thau lagoon (northern Mediterranean) and its growth and uptake characteristics measured for nitrate, ammonium, and urea. Although affinity constants did not indicate a preference for ammonium over nitrate, there was a strong inhibition of nitrate uptake by ammonium when both nitrogen (N) sources were present. Nitrogen budgets during growth in cultures revealed major imbalances between decreases in dissolved N and increases in particulate N, indicating excretion of dissolved organic N during the early part of the growth phase and uptake during the later part. A quasi-unialgal bloom in November 2001 (4 × 10 6 cells . L – 1 ) allowed measurements of uptake of nitrate, nitrite, ammonium, and urea; net and gross growth rate of A. catenella; and grazing rates on this organism. The affinity constants indicate that it is not a strong competitor for the N nutrients tested when these are in low concentrations (<10 μgat N.L - 1 ), compared with other members of the phytoplankton community. Indirect evidence from cultures indicate that dissolved organic N compounds could be important in triggering those blooms. Finally, the strongly unbalanced growth observed in the field indicates that A. catenella exhibits a storage rather than a growth response to a nutrient pulse and is adapted to low frequency events such as the passage of frontal disturbances. The disappearance of A. catenella was due to grazing that balanced growth at the peak of the bloom.