Simultaneous Multispectral Optical Measurement of Phytoplankton and Acoustic Measurement of Zooplankton

LONG TERM GOALS. The long-range scientific objectives of our program are to understand and characterize the underlying processes, both physical and behavioral, which govern the spatial distribution of phytoplankton and the foraging behavior of the predatory zooplankton. This will include mathematical models of the physics and biology. OBJECTIVES. Our objectives are to quantify the microscale and fine-scale vertical and horizontal patchiness of two taxa of phytoplankton and zooplankton in situ. This includes knowledge of the 3-d statistics of the patchiness of phytoplankton and zooplankton on scales 1 km, to a resolution of centimeters, and their relation to the ambient physical environment. The multispectral optical system will allow us to quantify the correlation of zooplankton with phytoplankton patches of differing species composition and the dynamic response of zooplankton to phytoplankton patchiness under a variety of conditions. APPROACH. We have developed a novel optical instrument Low light-level Underwater Multispectral Imaging System, LUMIS for measuring phytoplankton fluorescence in two wavebands, coincidently with the measurement of optical scattering and Raman inelastic scatter . The wavelengths resolved are 577 nm phycoerythrin, 680 nm chlorophyll a, 651 nm Raman and 532 nm for scattering the stimulating laser wavelength. This instrument was mounted on the same platform as the FishTV, an acoustic instrument allowing 3-d imaging of acoustic targets 6 mm at 445 kHz and 1 mm at 1.6 MHz. The two instruments were deployed simultaneously in Saanich Inlet, British Columbia, in August of 1997. The measurements with these two new instruments were supported by simultaneous collection of water samples for measurement of various phytoplanktonic taxa, and by vertical profiles obtained with a CTDfluorometertransmissometer package.