Suspended and settling particles in the Pacific

In order to understand the vertical transport of particulate matter, suspended and settling particles were collected along a meridional transect between 46degreesN and 35 S and an equatorial longitudinal transect between 135 E and 175 E in the Pacific. The low C(Organic)/N atomic ratios (<8.2) of suspended particulate organic matter (OM) and good correlation between particulate organic carbon (OC) and chlorophyll-a confirmed that the suspended particulate OM in the surface water was mainly produced by phytoplankton. Only 0.1-3.2% of primary production was transported to 1.3 km water depth in the boreal central Pacific. All data on settling particles (excluding deep trap data) showed strongly positive correlation between total mass and OM fluxes with high correlation factor of 0.93. Biogenic opal-producing plankton, mainly diatoms were responsible for most of the vertical transport of particulate OM in association with higher C(Organic)/C(Carbonate) ratios in the subarctic and equatorial hemipelagic regions in the Pacific. This vertical transport of settling particles potentially works as a sink of CO(2). In the transition zone during the May 1993, large difference between PCO(2) (<300 muatm) in the surface water and pCO(2) (340 muatm) in the atmosphere was actually due to enhanced particulate OM flux. Since the deep water of the Pacific is enriched in CO(2) and nutrients, upwelled seawater may tend to release COZ to the atmosphere. However, higher production of particulate matter could reduce the partial pressure of COZ in the surface water. Also terrestrial nutrients' inputs in the western equatorial Pacific have potential for the reduction of COZ in the surface water. (C) 2002 Elsevier Science Ltd. All rights reserved.