TY - JOUR T1 - Competition for phosphorus between two dinoflagellates: A toxic Alexandrium minutum and a non-toxic Heterocapsa triquetra A1 - Labry,Claire A1 - Erard-Le Denn,Evelyne A1 - Chapelle,Annie A1 - Fauchot,Juliette A1 - Youenou,Agnes A1 - Crassous,Marie-Pierre A1 - Le Grand,Jacqueline A1 - Lorgeoux,Benedicte AD - IFREMER, Ctr Brest, F-29280 Plouzane, France. UR - https://archimer.ifremer.fr/doc/00000/4067/ DO - 10.1016/j.jembe.2008.01.025 KW - Semi continuous culture KW - Batch culture KW - Ecophysiology KW - Pulse KW - Phosphorus storage KW - Dinoflagellates KW - Heterocapsa triquetra KW - Alexandrium minutum N2 - The understanding of the dominance of one species with respect to others is a pertinent challenge in HAB growth dynamics studies and the nutrient supply mode is one of the factors potentially involved. The competition for phosphorus (P) between a toxic species, Alexandrium minutum, and a non-toxic species, Heterocapsa triquetra, was studied (1) along a gradient of P depletion, (2) testing different P depletion degrees before a single PO4 supply and (3) experimenting different PO4 supply frequencies. In conditions Of PO4 depletion, H. triquetra stopped growing after two days both in monospecific and mixed batch cultures whereas A. minutum grew progressively from day 2 until the end of the experiment. This time-lag growth of A. minutum is associated to its ability to store P intracellularly and then mobilize it for cell division when P depletion becomes severe. Heterocapsa triquetra outcompeted A. minutum when it was submitted to less than three days of P depletion before the pulse. In contrast, A. minutum outcompeted H. triquetra after more than three days of depletion. This transition was related to the capacity for A. minutum to increase its cell PO4 uptake rate in a higher proportion to face potential PO4 supply. As a result of this physiological acclimatation to P starvation, A. minutum consumed the whole PO4 pulse supplied after 3 to 10 days of P depletion. This resulted in a reduction of H. triquetra growth. These two acclimatations were confirmed in a P limited semi-continuous culture experiment testing several PO4 supply frequencies (1, 2, 4, 6 day intervals). These experiments revealed that A. minutum is a "storage specialist" species for P, which uptakes PO4 pulses for luxury consumption, survives depletion periods and, then, utilizes P for cell growth. In contrast, H. triquetra is more a "velocity adapted" species, which utilizes PO4 just after supply to increase their cell division rate. (C) 2008 Elsevier B.V. All rights reserved. Y1 - 2008/04 PB - Elsevier JF - Journal of Experimental Marine Biology and Ecology SN - 0022-0981 VL - 358 IS - 2 SP - 124 EP - 135 ID - 4067 ER -