Investigating Diel Periodicity in Export Flux in the Gulf of Mexico Using a Particulate Imaging System
To estimate the diurnal periodicity in the biological pump, a floating array with a marine snow camera system at 150 m depth was used, and particles were imaged at a 40 second interval for a 24 to 30 hour period at five sites in the Gulf of Mexico in June 2017. Each image was processed to identify and size all the particles within the frame, which was then processed to determine diameter, an estimated volume, and settling speed for each particle. Using these parameters, particle mass was estimated using algebraically rearranged calculations for settling speed. Each hour during the deployment was binned and tested with a one-way analysis of variance. Three to four hour peaks of significantly increased particle counts were detected at each site with a defined baseline outside of these peaks, with the particle diameters not following this pattern. Most of these peaks occurred at noon local time, with one site demonstrating at midnight. The mass fluxes calculated using settling speeds were determined to be within these peaks, which contained at least 70% of the total flux. Using data from CTD casts performed while the array was deployed, the thermocline was observed changing in depth at least 7m at all sites. This was concluded to be the most likely cause of diel periodicity within the particulate flux, as relative currents around the camera were not shown to correlate with particle count
Mass Flux, Settling Speed, Particle Density, Marine Biology, Other Ecology and Evolutionary Biology
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