Comparing diatom and Alexandrium catenella/tamarense blooms in Thau lagoon: Importance of dissolved organic nitrogen in seasonally N-limited systems
|Author(s)||Collos Yves1, Jauzein Cecile1, Ratmaya Widya2, Souchu Philippe3, Abadie Eric4, Vaguer Andre1|
|Affiliation(s)||1 : Univ Montpellier 2, CNRS, IRD, UMR 5119,CC093, F-34095 Montpellier 5, France.
2 : Diponegoro Univ, Jawa Tengah, Indonesia.
3 : IFREMER, Lab Environm Ressource Morbihan Pays De La Loire, F-44311 Nantes 03, France.
4 : IFREMER, Lab Environm Ressource Languedoc Roussillon, F-34203 Sete, France.
|Source||Harmful Algae (1568-9883) (Elsevier Science Bv), 2014-07 , Vol. 37 , P. 84-91|
|WOS© Times Cited||20|
|Keyword(s)||Alexandrium catenella/tamarense, Non classical blooms, Organic nitrogen, Ammonium, Growth rate|
|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.|