METHODS AND PLATFORMS 



The work needs to be conducted from research vessels, perhaps focusing on transects from 

 the shelf to the slope at a limited number of stations (n=3) and depths (n=5 max. over slope). 

 Water can either be collected with bottles and processed via cross-flow filtration procedures on 

 board, or using in-situ CFF pumps now under development for OMP. 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



The strengths of this work include the ability to determine turnover rates of 

 DOC/COC/POC via thorium isotopes, as well as the ability to identify carbon sources and "ages" 

 using carbon isotopes. Weakness include the need to operationally separate colloids and particles 

 matter from seawater for chemical analysis, so our results are specific to the classes of 

 compounds separated by these techniques. There is also a considerable investment in people 

 power (and $) which is required for a single point in space and time, hence the spatial and 

 temporal coverage will be limited. 



STATUS OF RESEARCH 



We have just completed our first cruise where all of the above mention tracers will be 

 measured on the same samples (April cruise from George's Bank to Hatteras). Since most of the 

 analyses are time consuming, we will not have many results until this fall. Independent work 

 by the Pi's (Buesseler, Moran, Bauer, Druffel) suggests that the results will provide the first look 

 at colloid turnover rates and fate in a systematic survey of the US margin region. This new data 

 will prove quite valuable in planning the scope of future Hatteras work, as this field is still in 

 its infancy. 



Keywords: isotopes, carbon sources, turnover rates, fluxes 



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