AN ALTERNATIVE PROPOSAL: ACOUSTIC TECHNIQUES TO ASSES DETECTION AND MONITORING OF TOXIC ALGAL BLOOMS
An alternative methodology consisting in the application of acoustic techniques to asses detection and monitoring of toxic algal blooms is presented here. Successive steps in this direction led to already reported results [Blanc et al., 2000] achieved under the frame of a multidisciplinary research programme conducted in the Argentinean Naval Service of Research and Development. First efforts were focused in the examination of the acoustical scattering behaviour of single-species cultures of Skeletonema costatum. For this purpose a pulse-echo electronic equipment was developed, including home-made piezoelectric transducers with an operating frequency centred at 2.6 MHz. A slight modified Johnson's fluid-sphere model was used. Numerical Abundance estimates from at-lab acoustic determinations of Volume Backscattering Strengths were obtained. When they were compared with predicted values computed through the adopted model and traditional optical counting, satisfactory results were obtained. More recently, single cultures of dinoflagellates, namely, Gymnodinium sp., were selected to enable a further stage of acoustic laboratory measurements. Controlled observations of its optimum growth conditions along a six-months period have been performed. The effects of different patterns of light and temperature have been analysed. Simultaneous work on modifying existing models of Backscattering Cross-Sections to provide a realistic description of dinoflagellates physical properties is being performed