Discriminating between phytoplankton taxa by photoacoustics

We present here an application of the photoacoustic method for studying and discriminating between important phytoplankton taxa in suspension. The pho tosynthetic activity was studied by measuring the photoacoustic signal with and without background illumination. A linear dependence of the photoacous tic signal on the biomass of different algae was observed along with wavele ngth-dependent differences between the various phytoplankton taxa. The phot oacoustic signals from mixtures of pairs of taxa were measured at different ratios of the mixture components and at selected wavelengths at which the differences in absorption among the species were maximal. A linear dependen ce of the photoacoustic signal on the composition of each pair at the wavel engths studied was found. The results indicate the potential of the procedu re for determining the composition of phytoplankton communities and followi ng the effects of environmental parameters such as irradiance and nutrient status on the photosynthetic activity of phytoplankton.