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Quantifying the surface– subsurface biogeochemical coupling during the VERTIGO ALOHA and K2 studies
Citation
Boyd, PW and Gall, MP and Silver, MW and Coale, SL and Bidigare, RR and Bishop, JLKB, Quantifying the surface- subsurface biogeochemical coupling during the VERTIGO ALOHA and K2 studies, Deep-Sea Research Part 2, 55, (14-15) pp. 1578-1593. ISSN 0967-0645 (2008) [Refereed Article]
Copyright Statement
Copyright 2008 Elsevier
DOI: doi:10.1016/j.dsr2.2008.04.010
Abstract
A central question addressed by the VERtical Transport In the Global Ocean (VERTIGO) study was ‘What controls the efficiency of particle export between the surface and subsurface ocean’? Here, we present data from sites at ALOHA (N Central Pacific Gyre) and K2 (NW subarctic Pacific) on phytoplankton processes, and relate them via a simple planktonic foodweb model, to subsurface particle export (150–500 m). Three key factors enable quantification of the surface–subsurface coupling: a sampling design to overcome the temporal lag and spatial displacement between surface and subsurface processes; data on the size partitioning of net primary production (NPP) and subsequent transformations prior to export; estimates of the ratio of algal- to faecal-mediated vertical export flux. At ALOHA, phytoplankton were characterized by low stocks, NPP, Fv/Fm (N-limited), and were dominated by picoplankton. The HNLC waters at K2 were characterized by both two-fold changes in NPP and floristic shifts (high to low proportion of diatoms) between deployment 1 and 2. Prediction of export exiting the euphotic zone was based on size partitioning of NPP, a copepod-dominated foodweb and a ratio of 0.2 (ALOHA) and 0.1 (K2) for algal:faecal particle flux. Predicted export was 20–22 mg POC m−2 d−1 at ALOHA (i.e. 10–11% NPP (0–125 m); 1.1–1.2×export flux at 150 m (E150). At K2, export was 111 mg C m−2 d−1 (21% NPP (0–50 m); 1.8×E150) and 33 mg POC m−2 d−1 (11% NPP, 0–55 m); 1.4×E150) for deployments 1 and 2, respectively. This decrease in predicted export at K2 matches the observed trend for E150. Also, the low attenuation of export flux from 60 to 150 m is consistent with that between 150 and 500 m. This strong surface–subsurface coupling suggests that phytoplankton productivity and floristics play a key role at K2 in setting export flux, and moreover that pelagic particle transformations by grazers strongly influence to what extent sinking particles are further broken down in the underlying waters of the Twilight Zone.
Item Details
Item Type: | Refereed Article |
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Keywords: | primary production, subsurface export flux, particle transformations |
Research Division: | Earth Sciences |
Research Group: | Oceanography |
Research Field: | Chemical oceanography |
Objective Division: | Environmental Management |
Objective Group: | Marine systems and management |
Objective Field: | Measurement and assessment of marine water quality and condition |
UTAS Author: | Boyd, PW (Professor Philip Boyd) |
ID Code: | 95542 |
Year Published: | 2008 |
Web of Science® Times Cited: | 27 |
Deposited By: | IMAS Research and Education Centre |
Deposited On: | 2014-10-03 |
Last Modified: | 2014-11-11 |
Downloads: | 0 |
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