The Source and Fate of Primary Production in Relation to Carbon Fluxes on NOAA's Long Line Cruises

Francisco P. Chavez , Reiko P. Michisaki, Kurt R. Buck

N92S : Equatorial Pacific Spring 1992

CZSC (53k)

Seasonal composite of chlorophyll for the Summer, 1992 from the Coastal Zone Color Scanner (CZCS).

Figure 1. Cruise tracks for the spring equatorial Pacific cruise of 1992 (6k)

This cruise supports research funded by the NOAA Office of Global Programs (OGP) and the National Science Foundation (NSF), under the Ocean-Atmosphere Carbon Exchange Study (OACES) and the Joint Global Ocean Flux Study (JGOFS). The goal of the OACES project is to determine the source and sink regions regions of CO2 in the Equatorial and North Atlantic during the summer. Baseline of total carbon inventory in this region was established such that the uptake rate of atmospheric CO2 can be determined for future cruises. Our contribution to this project was to enhance the observations relevant to climate and global change with measurements of primary and new production in an attempt to quantify the effects of the biological system on the carbon and nitrogen cycle.

This is the first part of the 1992 Equatorial Pacific cruise, the second part took place in the fall. This cruise took place aboard the NOAA R/V MALCOLM BALDRIGE during a 13 week period, from February 24 to May 15, 1992. The cruise tracks and station locations are shown in Figure 1. There were three legs ; the leg 1 occupied 110° and 125°W during Feb. to Mar. 27, leg 2 occupied 170° during late March to mid April, and leg 3 worked the 140° line during mid April to mid May.

A total of 91 stations (station report, 10k) were sampled for chlorophyll a analysis at 8 depths in the upper 200 meters of the water column, at 12 of these stations POC profiles to 1000 meters were sampled. Profiles for chlorophyll and primary productivity (using 13C uptake) were taken at 64 stations using a kevlar line and Go-Flo bottles tripped at six depths in the euphotic zone. Also taken at 64 stations were surface particulate organic carbon (POC) and phytoplankton speciation samples, complete profiles for POC were taken at 20 stations and for phytoplankton speciation at 16 stations. the 15N incorporation experiments were carried out at 45 stations and microzooplankton grazing experiements were carried out at 15 stations.

An underway mapping system was deployed, providing a continuous record of fluorescence, PAR, GPS positions, and nitrate. Data from this cruise was processed by Monterey Bay Aquarium Research Institute (MBARI) and NOAA personnel.

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