Effects of small-scale turbulence on dinoflagellate ecophysiology

Memoria presentada por Gisela Llavería para obtener el título de Doctora por la Universidad de la Universitat Politècnica de Catalunya (UPC), realizada bajo la dirección de Dra. Elisa Berdalet del Institut de Ciències del Mar (ICM-CSIC).-- Tesis defendida en Barcelona el 20 de Noviembre de 2009. Excelente cum laude por unanimidad. Los capítulos de la tesi 1, 4, 5 y 6 han sido publicados como artículos científicos en revistas del SCI entre los años 2007 y 2011

Dinoflagellate proliferations seem to be often related to certain stability of the water column. Laboratory experiments have shown that small-scale turbulence can diminish the net growth rate and inhibit cell division, and simultaneously increase the cell size and the DNA and RNA content. The objective of this PhD Thesis was to explore direct effects of small-scale turbulence on physiological processes related to the cell and life cycles of dinoflagellates, and to investigate the underlying mechanisms in the observed responses. The gained knowledge should provide a better understanding of the development of their proliferations. The cell cycle of the dinoflagellate Alexandrium minutum was transiently arrested in the G2/M phase. It was explored whether such interference was due to an eventual alteration, due to turbulence, of the microtubular system implicated in the dinomitosis, whether ryanodine receptors were involved in the mechanotransduction pathway activated by this stimulus, and also whether a possible differential gene expression occurred under turbulence. Toxins and DMSP concentrations, the proportion of ecdysal cyst and the endoparasite Parvilucifera sinerae infection on dinoflagellates were also modulated by turbulence. Namely, infectivity decreased under shaking, and likely, asexual encystment did not constitute a preventive mechanism to infection. The suitability of some experimental systems for turbulence generation was also considerate. The orbital shaker is the most appropriate setup to carry out physiological studies on dinoflagellates, since the whole culture is exposed to turbulence, and cells cannot escape it. The present Thesis concludes that dinoflagellates prefer calm water column situations, since their physiology is sensitive to intense mixing

Spanish projects: TURFI (REN2002-01591/MAR), TURDITOX (CTM2005-03547/MAR), TURECOTOX (CTM2006-13884-C02-00/MAR) VARITEC (CTM2004-04442-C02). G. Llaveria fue becaria FPU del MICINN (2004-2008)