Systematics, Biodiversity and Evolution of Plants
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Thursday November 14th. 2024, 5 pm GMT+1

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Sylvain Gaillarda,b, Hamish J. Smalla, Nour Ayacheb, Simon Tanniouc, Philipp Hessc, Damien R ́eveillonc, Constance M. Harrisd, Thomas M. Harrisd, Gail P. Scotta, Alanna MacIntyrea, Kimberly S. Reecea

Assessment of allelochemical interactions between Alexandrium monilatum and other phytoplankton species

a Virginia Institute of Marine Science, William & Mary, P.O. Box 1346, Gloucester Point, VA 23062, USA
b Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
c IFREMER, PHYTOX unit, F 44000 Nantes, France
d Department of Chemistry, Vanderbilt University, Nashville, TN, 37235, USA

 

Species of Alexandrium can release bioactive extracellular compounds with allelopathic effects on other phytoplankton. The goniodomin producer Alexandrium monilatum forms blooms in the lower Chesapeake Bay, Virginia, US, that co-occur along with or immediately following a bloom of the dinoflagellate Margalefidium polykrikoides, which are often preceded by blooms of the dinoflagellate Akashiwo sanguinea. However, the allelopathic potential of A. monilatum and how it may affect bloom dynamics have not been studied. Using a rapid fluorescence-based bioassay, flow cytometry, and an assessment of immobilization, we determined the effects of A. monilatum culture supernatants and standards of goniodomins on M. polykrikoides, A. sanguinea, and the diatom Chaetoceros muelleri (included as a reference strain). We observed strain-specific effects of the activity on the maximum quantum yield of the photosystem II (Fv/Fm), the morphology, and the mortality of the diatom, as well as a negative effect on the motility of M. polykrikoides, while no effect was observed on A. sanguinea. The study of supernatant time- and temperature-stability, and the absence of a relationship between observed effects and goniodomin concentrations suggested the presence of additional unknown allelochemicals distinct from goniodomins. While A. monilatum is capable of allelopathic interactions in laboratory-based assays, proving the competitive advantage over M. polykrikoides in the environment will require further studies, which will provide a better understanding of the bloom dynamics of these dinoflagellates in the Chesapeake Bay.