FIGURE 9.1 Locations of sediment trap moorings used in this study.

this study, however, we will report only average fluxes for the time intervals of the trap deployments. In general, the deployment periods are for one year (Table 9.1), the minimum deployment necessary to encompass the known seasonal flux changes (Deuser and Ross, 1980).

Sodium azide concentrations of 15 g/l in the sample cups preserve the trap samples. Azide is an effective bactericide, and because of the high alkalinity of the cup solutions, CaCO3 tests (even aragonite) are very well preserved. Fischer et al. (1983) discusses the sample preparation procedures in detail. Organic carbon and CaCO3 data were measured by acid evolution of CO2 and detection with a LECO carbon analyzer (Weliky et al., 1983). Atomic absorption spectrophotometry and instrumental neutron activation were used for all other analyses.

We report particle fluxes and burial rates for 11 sites (Figure 9.1; Tables 9.2-9.4). There are four equatorial Pacific sites (H, M, S, and C). Flux data from sites H and M have previously been reported in Dymond and Lyle, 1985; Murphy and Dymond, 1984; Fischer et al., 1986; Walsh et al., 1988a, b. Data from sites C and S have been reported in Dymond and Collier, 1988. There are five sites off the west coast of the United States. MFZ is a California Current site just north of the Mendocino Fracture Zone (Fischer et al., 1983). Nearshore (NS), Midway (MW), and Gyre (G) form a California Current transect (42° N) from very productive waters influenced by coastal upwelling to the relatively unproductive, central gyre. JDF is located on the Endeavour Segment of the Juan de Fuca Ridge, a site of present day, intense hydrothermal discharge. Although the primary purpose of this mooring was definition of processes effecting the hydrothermal particle flux (Dymond and Collier, 1988; Dymond and Roth, 1988; Roth and Dymond, 1989), three sediment traps were placed above the hydrothermal effluent plume. These data define the biological and upper water column inputs to this part of the ocean. Two sites are in the Atlantic. Hatteras Abyssal Plain (HAP) is approximately 300 km off the east coast of the United States. Particle flux data from this site have been reported in Heggie et al. (1987). Nares Abyssal Plain (NAP) is a deep water site in the western Atlantic (Thomson et al., 1984).

Definition of particulate rain rate to the sea floor requires data on the particulate flux variations with depth. Dissolution and decomposition of sinking particles remove labile components. Heterotrophic organisms consume the settling detritus, metabolize a portion of the organic matter, and repackage remaining inorganic and nonnutritious components into rapidly sinking fecal pellets. In addition, inclusion of clay-sized particles into large marine snow aggregates enhances the flux of fine particles and alters the composition of settling particles. Horizontal advection and lateral down slope transport from continental margins also modify the flux and composition of the settling material. Distinguishing between distal and local resuspension effects is necessary to determine the rain rate to the sediment. Distal resuspension by nepheloid transport, contour currents, or turbidity currents may be sources of biogenic and nonbiogenic components to a site. Locally resuspended material collected in a sediment trap, however,



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