Variations in Total Mass and AA Fluxes

In the hemipelagic zone, average total mass flux (TMF) at site N2 was higher than that at site M1, and the vertical decrease in the average TMF at both sites was negligible (Fig. 3). Comparison of data from individual samples revealed that the deep trap sometimes recorded a lower TMF of settling particulate matter but at other times, higher ones. In contrast, at site M3 in the warm pool and M5 in the equatorial-upwelling zone, the deep traps recorded a higher TMF than the shallow traps throughout the sampling period. In addition, the traps at these sites recorded higher fluxes relative to those deployed at sites N10 and N3. AA fluxes in the hemipelagic zone were much lower at site M1 than at site N2. The range of variation in the M-series traps was much larger than that in the N-series traps (Gupta and Kawahata, 2002). The shallow trap at site M3 in the warm pool zone occasionally recorded a near-zero flux during September-October 1999 (Fig. 4). At site S11 in the Coral Sea, TMF varied from 4.2 to 58.7 mgm-2 d-1, with higher fluxes during the austral spring (August-September 1995) and at the beginning of the austral summer (October 1995) (Gupta and Kawahata, 2003a). TMF at site S12 in the Coral Sea varied from 6.8 to 17.7 mgm-2 d-1, with no particular seasonal trends. However, in the deep trap at site 12, TMF was occasionally higher than the corresponding sample in the shallow

Shallow Deep

Figure 3: Regional variations in average values of settling particle mass and amino acid fluxes in the western equatorial and south-eastern Pacific Ocean.

Shallow Deep

Shallow Deep

Figure 3: Regional variations in average values of settling particle mass and amino acid fluxes in the western equatorial and south-eastern Pacific Ocean.

trap. Nonetheless, the average TMF in the deep trap was lower than that in the shallow trap (Fig. 3) and varied from 2.8 to 11.7mgm" "2 d-1. TMF at site S13 varied from 6.3 to 68.4mgm" -2 d-1, with a strong seasonal signal in late spring (September-October 1995).

Higher TMF in deep traps, relative to shallow traps, has been observed by a number of other studies, and various explanations have been offered to account for the increase in particle flux with increasing water depth. Chemolithotrophic new production (Karl and Knauer, 1984; Roth and Dymond, 1989), aggregate formation due to zooplanktonic activity in deep waters (Walsh et al., 1988a), lateral advection from a nearby more productive region (Siegel et al., 1990) and contribution of re-suspended particles

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