HR: 1400h
AN: OS23E-08    [Abstracts]
TI: Laser-based fluorometer for real-time plankton mapping by an autonomous underwater vehicle
AU: * Bensky, T J
EM: tbensky@calpoly.edu
AF: California Polytechnic State University, Physics Department 1 Grand Ave, San Luis Obispo, CA 93407, United States
AU: Moline, M A
EM: mmoline@calpoly.edu
AF: California Polytechnic State University, Physics Department 1 Grand Ave, San Luis Obispo, CA 93407, United States
AU: Neff, B
EM: bneff@calpoly.edu
AF: California Polytechnic State University, Physics Department 1 Grand Ave, San Luis Obispo, CA 93407, United States
AU: Rohan, D
AF: California Polytechnic State University, Physics Department 1 Grand Ave, San Luis Obispo, CA 93407, United States
AU: Clemo, L
AF: California Polytechnic State University, Physics Department 1 Grand Ave, San Luis Obispo, CA 93407, United States
AB: We are constructing a laser-based chlorophyll fluorometer that will be integrated into a REMUS AUV platform. This poster will report on our construction progress and on the expected oceanographic data, based on bench testing with sea-water trials. The eventual REMUS deployment has forced many design constraints onto this work, in particular on power consumption and overall instrument volume. We feel as if we have reached an optimal and feasible design. The instrument itself consists of a 440 nm laser, which matches the blue absorption line of Chlorophyll-a (CHL-a), the primary green pigment in phytoplankton. The laser is pulsed at between 1 and 10 kHz with 50 ns-long pulses. We expect the laser to stimulate CHL-a fluorescence up to 5 meters from the vehicle in coastal waters. Stimulated fluorescence in the beam volume is imaged using a streak camera, which yields both spatial and temporal evolution of the fluorescence in a single shot. Hence, the instrument will enable real-time rapid spatial mapping of phytoplankton communities. Our experimental goal is to map plankton communities real-time for a few meters from the vehicle in a single shot. Our choice of the laser (small, battery operated), has 50 nanosecond flashes, spaced at 1 millisecond. Such pump light has thrown this work into a fluorometry regime unseen in previous in-situ work. With such short pump light flashes, we do not observe variable fluorescence in live sea-water, and the laser pulse is too long to resolve in situ fluorescent lifetimes. After a single actinic light pulse however, we are able to extract a flash saturation curve, yielding F₀ (minimal fluorescence) and F_sat (saturating fluorescence) with each shot of the laser. From this we are able to compute the phytoplankton photochemistry cross section, presumably of the PSII reaction center, nearly continuously along the vertical water traversed by the laser beam.
DE: 0480 Remote sensing
DE: 0649 Optics (4264)
DE: 4262 Ocean observing systems
DE: 4271 Physical and chemical properties of seawater
SC: Ocean Sciences [OS]
MN: 2007 Joint Assembly