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Seasonal cycles of phytoplankton and net primary production from Biogeochemical Argo float data in the south-west Pacific Ocean


Chiswell, SM and Gutierrez-Rodriguez, A and Gall, M and Safi, K and Strzepek, RF and Decima, MR and Nodder, SD, Seasonal cycles of phytoplankton and net primary production from Biogeochemical Argo float data in the south-west Pacific Ocean, Deep-Sea Research. Part 1, 187 Article 103834. ISSN 0967-0637 (2022) [Refereed Article]

Copyright Statement

2022 Elsevier Ltd.

DOI: doi:10.1016/j.dsr.2022.103834


We present annual cycles of chlorophyll a, phytoplankton carbon, nitrate and oxygen for Subtropical (STW), Subantarctic (SAW), and Subantarctic Mode (SAMW) waters near Aotearoa New Zealand from data collected by two Biogeochemical (BGC) Argo floats. We develop two simple models of depth-integrated net primary production (NPP), tuned against 14C-uptake measurements, to compare with Vertically-Generalised Production Model (VGPM) satellite-based estimates of NPP. One model is the simplest possible, and assumes production is proportional to light multiplied by chlorophyll a concentration. The second model modifies the light response profile to account for photoacclimation. In STW at 3035S, enhanced production is initiated in austral autumn when the mixed layer deepens to entrain nutrients into the photic zone. For about half the year, there is substantial production within a deep chlorophyll maximum that sits below the mixed layer. Consequently, depth-integrated NPP is only loosely related to surface biomass as imaged from satellite remote-sensing, and BGC Argo-based model estimates of depth-integrated NPP are about double VGPM estimates. In SAW at 4555S, production is initiated when vertical mixing decreases in austral spring. Production is largely within the mixed layer, and depth-integrated phytoplankton biomass and depth-integrated NPP follow surface phytoplankton biomass. Model estimates of depth-integrated NPP based on BGC Argo float profiles are comparable with VGPM estimates for the southern water masses.

Item Details

Item Type:Refereed Article
Keywords:primary production, BGC-Argo floats, physical control, Pacific Ocean, New Zealand, subtropical water, subantarctic water, subantarctic mode water
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Strzepek, RF (Dr Robert Strzepek)
ID Code:151096
Year Published:2022
Deposited By:Australian Antarctic Program Partnership
Deposited On:2022-07-18
Last Modified:2022-09-29

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