Oceanic upwelling and productivity in the eastern tropical Pacific

Journal Article · Sun Dec 01 04:00:00 EST 1991 · Limnology and Oceanography; (United States)

DOI:https://doi.org/10.4319/lo.1991.36.8.1834· OSTI ID:7111711

Fiedler, P C; Philbrick, V ^[1]; Chavez, F P ^[2]

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1. NOAA/NMFS Southwest Fisheries Science Center, La Jolla, CA (United States)
2. Monterey Bay Aquarium Research Inst., Pacific Grove, CA (United States)

An oceanographic survey of the eastern tropical Pacific Ocean in August-November 1990 found a productive, nutrient-rich, moderately high-chlorophyll surface layer in two oceanic upwelling regions: the equatorial divergence, especially east of the Galapagos, and the countercurrent divergence out to 105{degree}W, > 1,000 km west of the Costa Rica Dome. Although NO{sub 3} is not depleted in upwelling regions, relationships among nutrient concentrations and temperature in 1986-1988 data from the same area show that NO{sub 3} is the first macronutrient to be depleted in adjacent, less-productive regions. A three-dimensional, two-layer box model of NO{sub 3} flux within and into the euphotic zone gives estimated rates of new production that are {approximately}29% of measured rates of {sup 14}C phytoplankton production. Persistence of excess NO{sub 3} in the euphotic zone exceeds 1 yr under high-nutrient, low-chlorophyll conditions off the equator where weak upwelling, or downwelling, occurs. These results indicate substantial control or limitation of NO{sub 3} utilization and productivity in nutrient-rich oceanic regions of the eastern tropical Pacific.

• OSTI ID: 7111711
• Journal Information: Limnology and Oceanography; (United States), Journal Name: Limnology and Oceanography; (United States) Vol. 36:8; ISSN LIOCA; ISSN 0024-3590
• Country of Publication: United States
• Language: English

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