Primary production export flux in Marguerite Bay (Antarctic Peninsula): Linking upper water-column production to sediment trap flux

Keith Weston,Timothy D Jickells,Damien S Carson,Andrew Clarke,Michael P Meredith,Mark A Brandon,Margaret I Wallace,Simon J Ussher,Katharine R Hendry

doi:10.1016/j.dsr.2013.02.001

Abstract

A study was carried out to assess primary production and associated export flux in the coastal waters of the western Antarctic Peninsula at an oceanographic time-series site. New, i.e., exportable, primary production in the upper water-column was estimated in two ways; by nutrient deficit measurements, and by primary production rate measurements using separate 14C-labelled radioisotope and 15N-labelled stable isotope uptake incubations. The resulting average annual exportable primary production estimates at the time-series site from nutrient deficit and primary production rates were 13 and 16molCm−2, respectively. Regenerated primary production was measured using 15N-labelled ammonium and urea uptake, and was low throughout the sampling period.The exportable primary production measurements were compared with sediment trap flux measurements from 2 locations; the time-series site and at a site 40km away in deeper water. Results showed ∼1% of the upper mixed layer exportable primary production was exported to traps at 200m depth at the time-series site (total water column depth 520m). The maximum particle flux rate to sediment traps at the deeper offshore site (total water column depth 820m) was lower than the flux at the coastal time-series site. Flux of particulate organic carbon was similar throughout the spring–summer high flux period for both sites. Remineralisation of particulate organic matter predominantly occurred in the upper water-column (<200m depth), with minimal remineralisation below 200m, at both sites. This highly productive region on the Western Antarctic Peninsula is therefore best characterised as ‘high recycling, low export’.

Highlights

Biogeochemical processes in Antarctic coastal waters can exert important influences on both benthic and planktonic ecological phenomena, e.g. Karl et al (1991); Barnes and Clarke (1994); Prezelin et al (2000); Smith et al (2008)
Combining the short-term direct rate measurements of phytoplankton growth with the nutrient drawdown method, which integrates to some extent over space and time, allows an improved estimation of the areal annual exportable primary production for the Marguerite Bay region
The mixed layer depth (MLD) is an important control on productivity and export (Clarke et al, 2008) bloom magnitude and duration is the result of a complex interplay between light, mixing and the duration of sea-ice (Venables et al, in press)

Summary

Introduction

Biogeochemical processes in Antarctic coastal waters can exert important influences on both benthic and planktonic ecological phenomena, e.g. Karl et al (1991); Barnes and Clarke (1994); Prezelin et al (2000); Smith et al (2008). Despite a short phytoplankton growth period in these Antarctic shelf regions, the overall annual primary productivity is high relative to the Southern Ocean (Arrigo et al, 1998; Vernet et al, 2008). This is in part due to the presence of sufficient trace nutrients, e.g. dissolved Fe, in coastal Antarctic waters (Ardelan et al, 2010) in contrast to the Southern Ocean (Martin et al, 1990). Combining the short-term direct rate measurements of phytoplankton growth with the nutrient drawdown method, which integrates to some extent over space and time, allows an improved estimation of the areal annual exportable primary production for the Marguerite Bay region

Methods

Results

Discussion

Conclusion