experimental timescales of the grazing experiments are well-matched with the free-floating 

 sediment trap deployments of ~2 days. These experiments should be conducted within the 

 vicinity of the cluster mooring sites. These processes will be measured during seasonal cruises 

 to the study region off Cape Hatteras. 



METHODS AND PLATFORMS 



Laboratory experiments will be conducted in mesocosms with phytoplankton and 

 zooplankton species representative of the major taxa known to play a major role in coastal marine 

 systems. Grazing by microzooplankton and concomitant DOC production will be estimated using 

 the dilution technique of Landry and Hassett (1982). Bacteria will be DAPI-stained and 

 enumerated using epifluorescence microscopy (Porter and Feig, 1980), and phytoplankton and 

 protozoa will be counted using either epfiluoresence or inverted microscopy (Strom and Buskey, 

 1993). Bacterial production will be estimated from rates of protein synthesis as measured by the 

 incorporation of 3H-leucine (Kirchman et al., 1985). Tangential-flow ultrafiltration will be used 

 for separating DOC into various molecular sizes for chemical characterization (Benner, 1991). 

 Chemical characterizations of samples will include measurements of DOC by high-temperature 

 combustion (Benner and Strom, 1993), dissolved carbohydrates by spectrophotometry (Pakulski 

 and Benner, 1992), neutral sugars by HPLC (Mopper et al., 1992), dissolved amines by HPLC 

 (Gardner and St. John, 1991), and pigments by HPLC (Wright et al., 1991). 



STRENGTHS AND LIMITATIONS OF PROPOSED RESEARCH 



The proposed experiments will help elucidate the fundamental mechanisms and major 

 pathways of carbon flow between the autotrophic and heterotrophic components of marine food 

 webs. Knowledge of mechanisms and pathways of carbon flow is essential for determining 

 environmental factors that regulate the ultimate fate of carbon in the ocean. The proposed 

 grazing experiments require 1 to 2 days to complete so spatial coverage during cruises will be 

 limited and we must assume that the measured rates of DOC production and consumption are 

 representative for the general study region. 



STATUS OF RESEARCH 



This is a new project that will start on September 1, 1994. 



Keywords: DOC, zooplankton, grazing, phytoplankton 



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