debris likely occurs during a spring bloom period, we envision at least two seasonal cruises 

 corresponding to pre-bloom and early post-bloom, with an additional sampling during an 

 intermediate non-bloom interval. 



METHODS AND PLATFORMS 



Remotely obtained sediment box cores and bottom water samples (SPM, Chl-a/C org ratio) 

 represent the primary collection methods. Conditional topographic sampling using specifically 

 oriented samples obtained by submersibles may be used where possible in conjunction with other 

 investigators such as R. Jahnke and L. Benninger. Our emphasis will be on properties that can 

 potentially provide estimates of reaction rates and net fluxes, lend themselves to mapping over 

 large regions, and which can be related to planned water column measurements such as microbial 

 metabolic activity and suspended matter pigments. We propose to: 1) measure 234 Th, ( 7 Be will 

 be attempted) Chl-a, and biogenic Si0 2 on submersible and surface retrieved cores and bottom 

 water suspended matter. The resulting profiles will be used to estimate particle reworking rates 

 near the sediment-water interface, derive in situ rate constants for Chl-a and Si0 2 decomposition, 

 and model the likely reactive biogenic debris flux to the bottom for comparison to solute- based 

 estimates made predominantly by R. Jahnke. 2) We will take X- radiographs of sedimentary 

 structures in cores to evaluate likely modes and relative dominance of bioturbation or physical 

 transport processes at each site. 3) We will quantify both live and death assemblages of shell- 

 bearing benthos (molluscs, forams) and examine specific components of debris for indicators of 

 benthic deposition or dissolution of CaC0 3 . Patterns of live:dead:total abundances in principle 

 allow estimates of net dissolution or precipitation of benthic carbonate between sites and will 

 be factored into interpretation of COj/Oj flux balances. Comparison of live : dead carbonate 

 bearing infauna also provides insights into biological controls on mortality (i.e., predation) as 

 well as indicating lateral transport processes of biogenic debris. 4) Bacterial abundances will 

 be assessed by direct count techniques using epifluorescence microscopy and acridine orange 

 stained samples. Community average and dominate bacterial species-specific growth rates will 

 be evaluated by measuring rRNA content of individual cells and rRNA frequency of the total 

 population. P. Kemp's group at Brookhaven National Laboratory are developing rRNA specific 

 oligonucleotide probes to a subset of numerically and biomass dominant bacteria in coastal 

 sediments. We will work with them in using these probes to evaluate the population dynamics 

 of dominant metabolic sediment microbes in the study area and relate them to environmental 

 properties such as Corg flux. 5) We will attempt to measure net remineralization rates in 0-5 

 cm surface sediment (£C0 2 , NH 4 + ) using a whole core incubation technique (Aller and Mackin, 

 1989; Aller, et al., 1994) on retrieved cores at shallower water sites and in situ at any 

 submersible study stations. 6) In selected cases (i.e. muddy sediments, < 200 m depth), 

 biogenic irrigation will be measured using Br" tracer methods on shipboard incubated cores, in 

 order to further constrain benthic community influence on remineralization. These cores could 

 be used to estimate benthic 2 fluxes as required, but in general we do not plan extensive direct 

 solute flux measurements or detailed pore water profile work-ups. 



