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Potential drivers of sinking particle's size spectra and vertical flux of particulate organic carbon ( POC ): T urbulence, phytoplankton, and zooplankton
Author(s) -
Wiedmann Ingrid,
Reigstad Marit,
Sundfjord Arild,
Basedow Sünnje
Publication year - 2014
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2013jc009754
Subject(s) - photic zone , phytoplankton , oceanography , spring bloom , bloom , flux (metallurgy) , zooplankton , phytodetritus , environmental science , algal bloom , arctic , sediment trap , biogenic silica , particulates , atmospheric sciences , chemistry , benthic zone , water column , geology , diatom , nutrient , foraminifera , organic chemistry
Phytoplankton spring blooms in temperate and high‐latitude shelf seas are commonly associated with an enhanced particulate organic carbon (POC) export of aggregates from the euphotic zone. In contrast, a postbloom situation is usually linked to a predominant POC retention, where small cells (<10 μm) and strong grazing pressure prevail. This study aimed to examine impacts of turbulence, phytoplankton, bloom stage, and zooplankton abundance on the sinking particles' size spectra and POC flux to improve the understanding of the downward flux mechanisms in the upper 100 m. We deployed sediment traps, partly modified with gel jars, at four depths along a stratification and phytoplankton bloom gradient in the Barents Sea, an Arctic shelf sea. The highest POC export (60 m: 923 mg C m −2 d −1 ) was found in deep‐mixed, postbloom Atlantic influenced waters, despite the high grazer abundance (12,000 individuals m −3 ). Particle size spectra indicated that this flux was dominated by particles of 0.05–1.00 mm equivalent spherical diameter (ESD image ) with a POC: volume ratio matching a mixture of phytoplankton biomass and zooplankton fecal pellets. Large particles (0.5–2.8 mm ESD image ) dominated the flux at a stratified, late peak bloom station in Arctic Waters and a stratified, late bloom situation at the Polar Front, but with lower POC:volume ratio and POC flux (60 m: <823 mg C m −2 d −1 ). Accordingly, a high POC flux at the base of the euphotic zone is not necessarily driven by large phytoplankton aggregates, but can also occur during a postbloom situation in form of small fecal pellet fragments with high POC content.