Cross-basin differences in the nutrient assimilation characteristics of induced phytoplankton blooms in the subtropical Pacific waters.

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From: Biogeosciences(Vol. 18, Issue 3)
Publisher: Copernicus GmbH
Document Type: Brief article
Length: 334 words

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Abstract :

To better understand the nutrient assimilation characteristics of subtropical phytoplankton, deep-water addition incubation experiments were carried out on surface waters collected at seven stations across the subtropical North and South Pacific Ocean. These deep-water additions induced phytoplankton blooms with nutrient drawdown at all stations. The drawdown ratios of dissolved inorganic nitrogen (DIN) to phosphate (PO.sub.4) varied from 14.1 to 30.7 at the PO.sub.4 -replete stations in the central North Pacific (CNP) and eastern South Pacific (ESP). These ratios were similar to the range represented by the canonical Redfield ratio (16) through to typical particulate N:P ratios in the surface subtropical ocean (28). In contrast, lower DIN:PO.sub.4 drawdown ratios (7.7-13.3) were observed in induced blooms at the PO.sub.4 -depleted stations in the western North Pacific (WNP). The DIN:PO.sub.4 drawdown ratios in the PO.sub.4 -replete ESP were associated with eukaryote-dominated blooms, while those in the PO.sub.4 -depleted WNP were associated with eukaryotic and cyanobacterial blooms. The surplus PO.sub.4 assimilation, relative to DIN, by phytoplankton in the WNP was not expected based on their typical cellular N:P ratio and was likely due to the high PO.sub.4 uptake capability as induced by low-PO.sub.4 -adapted phytoplankton. The low- and high-P.sup.* (=PO4- DIN/16) regimes geographically corresponded to the low and high DIN:PO.sub.4 drawdown ratios in the WNP and the CNP or ESP, respectively. The basin-wide P.sup.* distribution in the oligotrophic Pacific surface waters showed a clear regional trend from low in the WNP (

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Gale Document Number: GALE|A651159827