Depending on the size and location of the study cube, we envision taking samples at an inshore, 

 midshelf, and offshore site along the north and south faces of the cube. 



Our long shelf studies will largely follow the pattern of our recently completed spring 

 cruise. We will survey the longshelf distribution by making 7 transects (approximate equal 

 spacing) perpendicular to the shelf between Georges Bank and Hatteras, as well as one or more 

 major estuaries (Hudson, Delaware, Chesapeake). Hydrocasts will be performed at 8-10 stations 

 of 5-10 mile spacing per transect beginning at the 15 m contour and extending to the 

 1500-2000m contour. At each station we sample water at 5-25m depth intervals. We will 

 propose 2 cruises in order to conduct these measurements in the spring (February/March) and 

 again in the late summer/early fall (August/September). 



METHODS AND PLATFORMS 



For sampling, we use a deck-mounted large volume pumping system to filter seawater 

 (<0.2um) into -200L barrels for ultrafiltration. DOM is concentrated to 1L by passing through 

 lKDalton or lOKDalton membranes, diafiltered, then frozen for return to the lab. We can 

 process 2-4 samples per day. Tangental flow filtration (0.3 or 0.8pm membranes) of smaller 

 volumes of seawater (4-20L) from Niskin Go-Flo Bottles is also performed for isolation of 

 particulate matter (for mass spectral characterization). The latter samples can be processed within 

 a few hours and therefore allow a more general survey type study, in which samples are 

 collected at a spatial and temporal resolution comparable to many bulk measurements. Sample 

 collection requires at least three (preferably four) people. For the longshore transport survey, 

 we make POC, PON, HPLC pigment, nutrient, fluorescence, and DOC analyses on discrete 

 samples. We also use underway fluorescence to monitor DOM and chlorophyll, and last spring 

 coordinated our efforts with NASA P-3 overflights and satellite AVHRR and CZCS imagery. 

 For the OMP field program, we would use our connections with NASA-GSFC to coordinate our 

 efforts with SeaWifs data. We are currently examining the potential of a fiber-optic DOM 

 fluorescence profiler as well as a mooring-based sensor for DOM fluorescence, although it is 

 unclear weather we will attempt to deploy these in the 1995-1996 time frame. 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



We are very keen on interfacing the longshelf survey with the detailed biogeochemical 

 and physical oceanographic investigations at the Hatteras study site. On this year's spring cruise 

 we observed large gradients in DOC between Georges Bank and Hatteras, and we suspect that 

 estuaries play a major role in the export of DOC from the shelf. We do not believe that either 

 approach will succeed in isolation. The focus on the Hatteras region makes sense from the 

 viewpoint of understanding basic recycling mechanisms and there is a large and variable signal 

 to be monitored. However, the study area is physically dynamic (as evidenced by AVHRR 

 imagery and spatial DOC concentrations) and DOC is so strongly influenced by sources and 

 inputs upshelf that some survey on a larger spatial scale is necessary. The importance of a 



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