PRINCIPAL 



INVESTIGATOR(S) Ian D. Walsh and Wilford D. Gardner 



Both at: Department of Oceanography 



Texas A&M University 

 College Station, TX 77843 



PROJECT TITLE OPTICAL ASSESSMENT OF LARGE MARINE PARTICLES: 



DEVELOPMENT OF AN IMAGING AND ANALYSIS 

 SYSTEM FOR QUANTIFYING LARGE PARTICLE 

 DISTRIBUTIONS AND FLUXES 



AMOUNT OF FUNDING FY 1993: $43 K 



SUMMARY OF GOALS 



The central goal of DOE's Ocean Margin Program (OMP) is to determine whether 

 continental shelves are quantitatively significant in removing carbon dioxide from the atmosphere 

 and isolating it via burial in sediments or exporting it to the open ocean (Program Announcement, 

 1991). A major component of the OMP will be to measure carbon flux on the shelf and across 

 the shelf to the slope and open ocean. We are developing a video and optical instrument package 

 (LAPS: Large Aggregate Profiling System) and the analytical techniques to precisely measure 

 a wide spectrum of the large aggregate population of particles in the shelf/slope environment 

 This particle population, encompassing the "marine snow" size particles (diameters > 0.5 mm), 

 is thought to be the major pathway of material flux in the ocean (McCave, 1975; Asper, 1987; 

 Walsh and Gardner, 1992). Our goal is to use aggregate abundance and size spectrum data along 

 with the CTD, beam attenuation and fluorescence data collected with our instrument package to 

 collect data rapidly, repeatedly and accurately such that it is both linkable to carbon flux and 

 usable in biophysical models. Additionally, measurements of particle flux will be made with 

 sediment traps deployed on the continental slope in conjunction with the physical oceanography 

 program. The combination of profiles and sections of aggregate data along with the measured 

 mass flux and chemistry from the sediment traps will allow for a robust estimate of the mass 

 transport and flux of organic carbon via the aggregate pathway. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



The LAPS can measure aggregate abundance with high spatial and temporal resolution. 

 The camera/strobe settings are adjustable and can be set to accommodate deep casts or shallow 

 casts. Generally, images will be acquired at a rate of 1 per meter on shallow casts, and 1 per 3 

 to 5 meters on deep casts (>500 m). The length of time of the cast is dependent on the depth and 



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