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- Title
- Iron, primary production and carbon-nitrogen flux studies during the JGOFS North Atlantic bloom experiment,
- Description
- Primary production was measured every other day towards the end (18-31 May) of the 1989 North Atlantic spring bloom. Rates varied with light and averaged 90.4 mmol C m -2 day -1 at the 47°N, 20°W station. Productivities measured south of Iceland (59°30′N, 20°45′W) were somewhat lower, averaging 83.6 mmol C m -2 day -1. Carbon and nitrogen fluxes were estimated using free-floating, VERTEX type particle trap arrays. To obtain mean rates representative of the North Atlantic spring bloom, flux data from three trap deployments were combined and fitted to normalized power functions:. mmol C m -2 day -1 = 14.35 (z/100) -0.946, mmol N m -2 day -1 = 2.34(z/100) -1.02, with depth z in meters. Regeneration rates were:. mmol C m -2 day -1 = 0.136(z/100) -1.946, mmol N m -2 day -1 = 0.0239(z/100) -2.02. The carbon export rate from the upper 35 m for the entire NABE study period (24 April to 1 June) was 39 mmol m -2 day -1. This value divided by the averaged productivity for the entire study (86 mmol N m -2 day -1) gave an F-ratio of 0.45. Concentrations of Cu, Fe, Ni, Pb and Zn were determined in water samples provided by JGOFS NABE scientists involved with primary productivity measurements. Although little contamination was observed for Cu, Ni and Pb, relatively large amounts of Zn (10 nmol kg -1) were found in some cases. In subsequent studies it was learned that this quantity of Zn can depress productivity rates by 25%. North Atlantic dissolved Fe concentrations were similar to those occurring in the Pacific (surface = 0.07; deep = 0.5-0.6 nmol kg -1). Although no evidence of Fe deficiency was found in enrichment experiments, the addition of nmol amounts of Fe did increase CO 2 uptake and POC formation by factors of 1.3-1.7. In this region, most of the phytoplankton's Fe requirement is probably met via the lateral transport of Fe from distant continental margins., Cited By (since 1996):170, CODEN: DSROE, ,
- Author
- Martin, Fitzwater, Michael Gordon, Hunter, Tanner
- Date
- 1993-01-01T00:00:00Z
- Title
- Northeast Pacific iron distributions in relation to phytoplankton productivity,
- Description
- Dissolved and particulate Fe concentrations, measured at three deep ocean stations on a 1600 km inshore-offshore VERTEX transect, were compared with those found at four shallow California continental margin stations. The three VERTEX profiles shared similar features: very low dissolved Fe levels (<0.1 nmol kg -1) in surface waters, increasing amounts with depth, and maxima (∼1.0-1.3 nmol kg -1) in association with the oxygen minimum. In contrast, concentrations as high as 9 nmol kg -1 of dissolved Fe were found at the shallow margin stations, in association with elevated levels of Mn (17 nmol kg -1) and Co (200 pmol kg -1). Inshore and offshore Fe distributions were evaluated in relation to the phytoplankton's requirement for this essential element. Local shelf diagenetic Fe input appears to be adequate for phytoplankton growth even in environments where increased demand results from the upwelling of major nutrients. However, the Fe laterally mixed out into the ocean's interior within the oxygen minimum and supplied to the surface via vertical mixing processes provides only a few percent of open ocean phytoplankton demand; the other 95% must be provided by atmospheric input. We also consider environments in which Fe supplies may be limiting phytoplankton growth; i.e. surface waters of the Subarctic and Antarctic, where major nutrients are never depleted. We postulate that atmospheric Fe input rates are not high enough to meet the elevated phytoplankton demand resulting from offshore major nutrient upwelling. As a result, major nutrient depletion occurs only along continental margins and ice edges, where Fe supplies should be adequate. Atmospheric dust concentrations were one to two orders of magnitude higher in glacial times than those in the present and last interglacial periods. The lower glacial atmospheric CO 2 levels, which resulted from the increased biological utilization of major nutrients at high latitudes, may have been stimulated by the enhanced availability of atmospheric Fe. © 1988., Cited By (since 1996):241, ,
- Author
- Martin, Michael Gordon
- Date
- 1988-01-01T00:00:00Z