Harmful Algal Blooms in Thin Layers


Thursday, October 27, 2011
Redfield Auditorium - 12:00 Noon
Dr. Lourdes Velo Suarez
Postdoctoral Fellow, WHOI, AOPE Department

Dinophysis spp. cells—producers of DSP toxins—and some especies of the diatom genus Pseudo-nitzschia—producers of ASP toxins—tend to aggregate during thermo-haline stratification conditions in thin layers. These “thin layers” can be associated to physical microstructures in the water column. It is very difficult to sample these layers and determinate the micro-distribution of the key organisms with conventional sampling instrumentation (CTDs, oceanographic bottles, plankton pumps, etc.). This study focus on the development, maintenance and dispersion of thin layers of harmful algal blooms especies during 3 multidisciplinary cruises in the Rías Baixas and the Bay of Biscay between 2003 and 2007. For the first time in the area, the population dynamics (division rate, viability frequency, mortality) of toxic microalgae and their behavior (vertical migration, mixotrophic processes...) are studied with the same spatio-temporal scale than the fine-scale hydrodynamics processes (current intensity and direction; vertical diffusion and turbulence).  The application of sophisticated sampling instrumentation, such as the “particle size analyzer profiler” (IPSAP) and the “fine scale sampler” (FSS) from IFREMER, together with the fine-scale description of the physical environment by acoustic profilers (ADCP y ADV) and undulating towed CTDs (SCANFISH), allow us to characterize these layers and the organisms aggregated within these structures using appropriate tools. These observations are complemented with the micro-manipulation of live microalgae cells (with and without fluorochromes added) in order to study their physiological status.