Interannual variability of vertical particle fluxes in the Ross Sea (Antarctica)

Francesca Chiarini,Lucilla Capotondi,Mariangela Ravaioli

doi:10.3897/natureconservation.34.30732

Abstract

This study presents new data on biogenic and terrigenous particle fluxes collected by an oceanographic mooring (Mooring A) deployed in the south-western Ross Sea (Antarctica) in the frame of the Italian Long-Term Ecological Research network (LTER-Italy). Results from the years 2005 and 2008 document high mass fluxes during the summer and early autumn seasons, not coincident with the algal bloom. Downward particle fluxes exhibit a high inter-annual variability of both particulate fluxes and composition that seem related to the different factors as the phytoplankton increases, occurring between the beginning of February and the end of March, to the variations in the sea ice extent and to the resuspension and/or lateral advection processes. The flux variability may have been influenced by Iceberg B-15 that resided in the investigated area between 2000 and 2005. The decoupling of biogenic silica and organic carbon cycles is documented by differences in the rates of their respective key processes: biogenic silica dissolution and organic carbon degradation.

Highlights

The Ross Sea is the region with the highest values of primary production and carbon sequestration through the biological pump in the Southern Ocean (Arrigo et al 2008a; Hoppe et al 2017)
As hypothesised in previous studies, the main driving force(s) responsible for the observed time lag could be: i) the time lag between the growth of phytoplankton and zooplankton community development (Dunbar et al 1998; Smith and Dunbar 1998; Boyd and Newton 1999); ii) a late diatom bloom associated with winds or a pulse of iron (Collier et al 2000; Peloquin and Smith 2007), and iii) small or low density aggregates or particles that sink at a slower rate in the water column (Smith and Dunbar 1998; Becquevort and Smith 2001)
The peaks of mass and biogenic fluxes were recorded in February and March, delayed by one/two months from the algal blooms that usually occur in December/ January, related with the processes of ice formation and melting

Summary

Introduction

The Ross Sea is the region with the highest values of primary production and carbon sequestration through the biological pump in the Southern Ocean (Arrigo et al 2008a; Hoppe et al 2017) It represents a key area for investigating changes in primary productivity and their relationship with sea ice cover, physical and chemical parameters of the water column and the availability of nutrients as the iron supply. All these parameters affect the phytoplankton blooms, the zooplankton grazing and, both retention and export of carbon within the water column and at the seafloor (Frignani et al 2000). Previous sediment trap data from Antarctic and Arctic seas suggested a close temporal coupling between the spring-summer phytoplankton blooms and high particle flux (Collier et al 2000; Anadon and Estrada 2002; Fischer et al 2002; Arrigo et al 2008b; Ducklow et al 2008, 2015; Honjo et al 2010; Forest et al 2011; Sampei et al 2012; Weston et al 2013)

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Discussion

Conclusion