event-related processes against a background of "normal", seasonally varying processes. 

 Sampling would focus on the mid-winter storm events responsible for transport in the benthic 

 boundary layer as well as instigation of blooms. The spring bloom may be responsible for a 

 majority of the annual input to the benthos; the summer stratification period may represent a 

 minimum input rate to the sea floor. 



i. Huxes across the sediment-water interface. 



Studies of the exchange of nutrients and carbon across the sediment-water interface will 

 play an important role in assessing carbon dynamics on the continental shelf and role of the 

 ocean margin in sequestering carbon from the atmosphere. Significant exchange of nutrients 

 and carbon may occur through the transport of dissolved, colloidal, or particulate materials 

 across the sediment surface and may directly or indirectly influence many aspects of 

 biogeochemical cycles on the shelf. These aspects include: nutrient inputs to shelf waters (via 

 dissolved and particulate exchange processes); nutrient losses from the shelf system including 

 burial and sedimentary denitrification; remineralization of organic matter; production of 

 particulate organic matter through benthic primary, chemolithotrophic , or secondary 

 production; and standing stock of water column particles. 



In addition to these specific processes, sea floor flux studies can be used to constrain 

 other processes that are important in determining the ultimate fate of shelf-derived organic 

 matter. These include the mean particulate flux of organic matter to the sea floor, the export 

 of particulate materials from the shelf, and the integrated net reaction rates in sediments 

 including benthic primary production and respiration. 



A variety of factors complicate studies of benthic exchange on continental shelves. For 

 example: 1. A wide range of redox conditions are possible within a small geographic setting 

 complicating the development of quantitative models relating the rates of diagenetic processes 

 to benthic fluxes. 2. Shelf sediments contain abundant macrobenthic organisms that actively 

 transport substrates and solutes through surface sediments. Since transport mechanisms are 

 diverse and difficult to accurately parameterize, these activities also complicate the 

 construction of models and the interpretation of results. 3. Many shelf regions are presenfly not 

 accumulating sediments and are subject to sediment resuspension events. It is therefore 

 difficult to assess particle input rates. 4. Because of frequent exposure to high current 

 velocities and turbulent energies, many regions are depleted in fine-grained sediment particles 

 and enriched in sands. Such sediments are difficult to core and sample for pore waters. 

 Because of the high permeability of sandy sediments, hydrodynamic events may influence pore 

 water solute transport. This may be the result of pumping due to wave action, enhanced 

 dispersion rates caused by horizontal pressure gradients from waves, and/or wave-induced flow 

 through vacant worm biurows. 5. Shelf sediments are exposed to a variety of temporally- 

 varying conditions, inputs and forces. Examples include seasonal changes in sediment 

 resuspension, particle flux, and temperature/metabolic rates. Temporal variability in sediment 

 and pore water properties wUl be more extreme than in sheltered inshore environments or at 

 slope depths; strategies for both sampling and interpretation must take this into account. 



Innovative techniques wiU be required to measure benthic fluxes in this environment. For 

 example, to include wave induced near-bottom turbulence and benthic photosynthesis, clear 

 flexible chambers may be used. The measurements will be interpreted in the context of BBL 

 physics, biological community structure, and water column input events. 



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