the larger metazooplankton will be determined by moored and ship-mounted acoustic Doppler 

 current profilers recording backscatter intensity, with backscatter intensity and seasonal 

 variability in species composition verified by net tows. Investigation of transformations of 

 organic matter which potentially store and transfer carbon from one season to another (i.e., 

 lipid synthesis and mobilization) and investigation of growth rates (i.e., egg production) will 

 be used to develop size-specific, species-specific, and season-specific algorithms. Water 

 column rates of grazing and growth, and their seasonal variability and fluctuation in response 

 to physical forcing, will be obtained by combining acoustic estimates of biomass with 

 algorithms derived from measured rates of transformation. 



Grazing rates of calanoid copepods, including copepodid stages and adult females, will be 

 quantified through shipboard experiments, using bottle incubations with hand-sorted specimens. 

 The planned approach is indirect as it uses growth over 24 hours to estimate the ingested 

 amount through back calculation. Auto- and heterotrophic cells are considered as being the 

 main food source. Combining these ingestion estimates with abundance and distribution data 

 will result in an estimate of grazing of the copepod community. Research will also be 

 directed to develop methods to (a) obtain time-series of the abundance and distribution of 

 gelatinous zooplankton and small metazooplankton by way of an optical zooplankton counter, 

 and (b) obtain real-world feeding rates. 



G. Production of DOC 



Molecular tools for determining the physiological state of individual phytoplankton ceUs 

 are under development, using phytoplankton cultures representative of major bloom-forming 

 taxa from the Atlantic and Pacific continental shelf envkonments to correlate the mean and 

 variance of cell health parameters with rates of DOC production and sinking rates. Cell health 

 markers under development include photosynthetic activity by autoradiography, lipid content 

 using the fluorescent stain Nile Red, and cell viability using the fluorogenic esterase substrate 

 Calcein-AM in combination with DNA detection using ethidium homodimer, a nuclear stain 

 which does not penetrate the cell membrane of intact cells. 



In field studies, major taxa of large phytoplankton (> 10 |xm) will be identified that 

 contribute directly to sedimentary flux off the shelf. The dominant phytoplankton identified in 

 water column samples (vertical net tows and samples from discrete depths) will be compared 

 with their contribution to material in 500 m sediment traps. These water column samples will 

 be collected throughout the year, with highest temporal resolution during the period of the 

 spring bloom, and will also provide a basis for evaluating the shelf-wide importance of taxa 

 which are dominant at study sites selected for intensive biological sampling (eg. 

 characterization of DOC production and cell health). The health of cells in populations of 

 these taxa will be evaluated using molecular probes, during different periods of the year and at 

 different locations on the shelf, to quantify the flux of primary photosynthate from 

 phytoplankton into pools of DOC. 



A method will be developed for the measurement of DOC production during grazing. The 

 proposed method would decouple DOC production from bacterial uptake by preconcentrating 

 zooplankton of various size fractions, then adding increasing amounts of the concentrate to 

 natural water samples to yield a concentration series. Bottles would be sampled at the 

 beginning and end of an incubation period. The net changes in DOC concentration, 



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