Comparison of acoustical and optical zooplankton measurements using an acoustic scattering model: A case study from the Arctic frontal zone

• Published in: Polish Polar Research
• Main Authors: Szczucka Joanna, Trudnowska Emilia, Hoppe Łukasz, Błachowiak-Samołyk Katarzyna
• Format: Article in Journal/Newspaper
• Language: English
• Published: Polish Academy of Sciences 2016
• Subjects: Arctic; Svalbard; zooplankton; high-frequency echosounding; sound scattering model; Geology; QE1-996.5; Polar Research; Zooplankton; Spitsbergen
• Online Access: https://doi.org/10.1515/popore-2016-0008; https://doaj.org/article/4f55bcf3f61a435db6cf9eebbf9a26ac

High-frequency acoustic measurements supplemented by a modern optical method, Laser Optical Plankton Counter (LOPC), allowed us to perform a comparative analysis through the application of a mathematical model. We have studied the correspondence between measured and modelled echoes from zooplankton aggregations consisted mainly of two Calanus species. Data were collected from the upper 50 m water layer within the hydrographical frontal zone on the West Spitsbergen Shelf. The application of a “high-pass” model of sound scattering by fluid-like particles to the distribution of zooplankton sizes measured by LOPC resulted mostly in very good agreement between the measured (420 kHz BioSonics) and modelled values, except for cases with very low zooplankton abundance or with occurrence of stronger scatterers (e.g. macrozooplankton, fish). An acoustic model validated for the elastic parameters of zooplankton confirmed that particles smaller than 1mmin diameter, although highly abundant, did not contribute significantly to the sound scattering process at a frequency of 420 kHz. The implementation of diverse complementary methods has great potential to obtain high spatial and temporal resolution in zooplankton distribution studies; however, their compatibility has to be tested first.