Tesis doctoral de Sílvia Anglés Calvo
This thesis is aimed at contributing to the knowledge on dinoflagellate (a phytoplankton group) population dynamics by integrating the planktonic and benthic phases. The main goal was to evaluate the role of the different life-cycle stages using methodologies that involve observation and experimentation in natural field conditions. In paper 1, the lisst-100x particle-size analyzer was used to examine the high spatio-temporal variability of a phytoplankton population dominated by the high-biomass species alexandrium taylori at la fosca beach (nw mediterranean). The high-resolution temporal data allowed the high variability in abundance to be related over a short time scale to the diel vertical migration of the phytoplankton population. Lisst-100x measurements of vegetative cells coupled with simulations obtained using the physical numerical model showed that surface-water circulation, determined by the prevailing wind regime, influences vegetative cell distribution within the surface waters of the beach. In paper 2, the dinoflagellate resting cyst bank in the sediments of two coastal embayments (arenys de mar harbor and the gulf of olbia, nw mediterranean) was analyzed and compared. Results showed that the diversity of cyst-producing species in their respective seed banks was high, hosting a greater number of species than recorded in the vegetative population of both sites. In addition, 10 morphotypes not previously described in the literature were identified. The vegetative cells that germinated from some of these morphotypes probably correspond to new species and the descriptions of them are undergoing. Paper 3 evaluated the spatio-temporal distribution of a. Minutum resting cysts in arenys de mar harbor in relation to the point source of resting-cyst formation (the distribution of vegetative cells), seiche-forced resuspension, and sediment granulometry. The spatial distribution of the vegetative cell bloom during the production of resting cysts within the harbor largely determined the sediment area where the cysts initially settled. During the periods in which resting cysts were not produced, they accumulated in areas where fine sediment fractions, mainly clays, tended to collect, confirming that hydrodynamic and sedimentary processes largely controlled their secondary dispersal. Seiches were identified for the first time as a major mechanism of sediment and resting cyst resuspension in marine semi-enclosed systems. Moreover, seiche-forced resuspension was observed to influence the horizontal and vertical distributions as well as the abundance of resting cysts in the sediment. In papers 4 and 5, the in situ germination (excystment) and resting cysts formation (encystment) of a. Minutum and a. Tamarense complex have been quantified, and the results integrated with those describing the dynamics of planktonic and benthic phases in order to gain insight into the population dynamics of these species. The excystment patterns were incessant germination (a. Minutum) and synchronous (a. Tamarense complex). The encystment process initiated at early bloom stages in the two alexandrium species, with encystment fluxes observed over the bloom phases of exponential growth, maintenance and decline. Physico-chemical factors did not appear to modulate encystment of either species. Resting cyst formation was observed when vegetative cell abundance reached 103104 cells l-1, and involved a low proportion of vegetative cells. There was a high correlation between resting cyst and vegetative cell abundances for a. Minutum. By combining planktonic- and benthic-phase dynamics with analyses of in situ transitions, this thesis has provided new insights into dinoflagellate population dynamics, including a new description of the life-cycle strategy of an alexandrium species.
Datos académicos de la tesis doctoral «Role of life cycle stages in dinoflagellate population (paper dels estadis del cicle de vida en la dinÁ mica de poblacions de dinoflagel.lades«
- Título de la tesis: Role of life cycle stages in dinoflagellate population (paper dels estadis del cicle de vida en la dinÁ mica de poblacions de dinoflagel.lades
- Autor: Sílvia Anglés Calvo
- Universidad: Barcelona
- Fecha de lectura de la tesis: 21/12/2010
Dirección y tribunal
- Director de la tesis
- Esther Garcés Pieres
- Tribunal
- Presidente del tribunal: Marta Estrada miyares
- Ana Amorim (vocal)
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