Vertical and latitudinal variations in amino acid fluxes and compositions of settling particles along 175°E in the North Pacific Ocean

Settling particles collected by sediment traps deployed for about one year (1993–94) at four sites along 175°E longitude in the central North Pacific have been analyzed for amino acids (AA) and amino sugars (or hexosamines, HA). These compounds account for about 12.5–27.9% of particulate organic carbon flux to the deep ocean. Biogeochemical indicator parameters varied in the range comparable with similar studies conducted in other oceanic sites. Correlations between non-protein AA (β-alanine and γ-aminobutyric acid) and flux parameters indicate repackaging of settling particulate organic matter (POM) around intermediate water depth (below 1500 m) at all trap sites. Mean values of indicator parameters in the shallow trap differ significantly (Student’s t-test; p < 0.03) from those in deep traps at the same site. Latitudinal trends in POM flux and its labile composition suggest that relatively fresh POM is being deposited at a higher rate in the subarctic area of the Pacific. However, this trend is not so clear in deep traps, probably due to the influence of bioactive transport and deposition of laterally advected particles in these traps. Total and particulate organic carbon fluxes normalized to primary productivity estimates show a sharp rise in efficiency of the biological pump towards the subarctic area, which is responsible for enhanced fluxes of particles with a high labile content to the deep ocean in this part of the Pacific.