Dynamics of an intense diatom bloom in the Northern Antarctic Peninsula, February 2016

Raul Rodrigo Costa, Carlos Rafael Borges Mendes, Virginia Maria Tavano, Tiago Segabinazzi Dotto, Rodrigo Kerr, Thiago Monteiro, Clarisse Odebrecht, Eduardo Resende Secchi

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Abstract

Diatoms are considered the main base of the Southern Ocean food web as they are responsible for more than 85% of its annual primary production and play a crucial role in the Antarctic trophic structure and in the biogeochemical cycles. Within this context, an intense diatom bloom reaching > 45 mg m−3 of chlorophyll a was registered in the Northern Antarctic Peninsula (NAP) during a late summer study in February 2016. Given that nutrient concentrations and grazing activities were not identified here as limiting factors on the bloom development, the aim of this study was to evaluate the effect of water column structure (stability and upper mixed layer depth) on the phytoplankton biomass and composition in the NAP. The diatom bloom, mainly composed by the large centric Odontella weissflogii (mostly > 70 μm in length), was associated with a local ocean carbon dioxide uptake that reached values greater than −60 mmol m−2 d−1. We hypothesize that the presence of a vertically large water column stability barrier, just below the pycnocline, was the main driver allowing for the development of the intense diatom bloom, particularly in the Gerlache Strait. Contrarily, a shift from diatoms to dinoflagellates (mainly Gymnodiniales < 20 μm) was observed associated with conditions of a highly stable thin layer. The results suggest that a large fraction of this intense diatom bloom is in fast sinking process, associated with low grazing pressure, showing a crucial role of diatoms for the efficiency of the biological carbon pump in this region.
Original languageEnglish
Pages (from-to)2056-2075
Number of pages20
JournalLimnology and Oceanography
Volume65
Issue number9
Early online date18 Mar 2020
DOIs
Publication statusPublished - 1 Sep 2020

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