Abstract
Abstract. The West Antarctic Peninsula (WAP) exhibits strong spatial and temporal oceanographic variability, resulting in highly heterogeneous biological productivity. Calcifying organisms that live in the waters off the WAP respond to temporal and spatial variations in ocean temperature and chemistry. These marine calcifiers are potentially threatened by regional climate change with waters already naturally close to carbonate undersaturation. Future projections of carbonate production in the Southern Ocean are challenging due to the lack of historical data collection and complex, decadal climate variability. Here we present a 6-year-long record of the shell fluxes, morphology and stable isotope variability of the polar planktic foraminifera Neogloboquadrina pachyderma (sensu stricto) from near Palmer Station, Antarctica. This species is fundamental to Southern Ocean planktic carbonate production as it is one of the very few planktic foraminifer species adapted to the marine polar environments. We use these new data to obtain insights into its ecology and to derive a robust assessment of the response of this polar species to environmental change. Morphology and stable isotope composition reveal the presence of different growth stages within this tightly defined species. Inter- and intra-annual variability of foraminiferal flux and size is evident and driven by a combination of environmental forcing parameters, most importantly food availability, temperature and sea ice duration and extent. Foraminiferal growth occurs throughout the austral year and is influenced by environmental change, a large portion of which is driven by the Southern Annular Mode and El Niño–Southern Oscillation. A distinct seasonal production is observed, with the highest shell fluxes during the warmest and most productive months of the year. The sensitivity of calcifying foraminifera to environmental variability in this region, from weeks to decades, has implications both for their response to future climatic change and for their use as palaeoclimate indicators. A longer ice-free season could increase carbonate production in this region at least while carbonate saturation is still high enough to allow for thick tests to grow.
Highlights
The West Antarctic Peninsula (WAP; Fig. 1) is a highly climatically sensitive region, characterised by strong seasonal and interannual variability in atmospheric, cryospheric and oceanographic conditions (Martinson et al, 2008)
Neogloboquadrina pachyderma sensu stricto (Nps) was the only foraminiferal species found in the sediment trap samples
Nps flux displays a double peak in some years (Fig. 2; for weekly averaged data see Supplement Fig. S1, calculated using Gyldenfeldt et al, 2000), similar to that observed in the North Atlantic by Tolderlund (1971) and Jonkers et al (2010)
Summary
The West Antarctic Peninsula (WAP; Fig. 1) is a highly climatically sensitive region, characterised by strong seasonal and interannual variability in atmospheric, cryospheric and oceanographic conditions (Martinson et al, 2008). The extreme environments of the WAP make these species vulnerable to seasonal and regional changes in food availability and water chemistry as a result of variable carbonate ion saturation states and overall low saturation (Lencina-Avila et al, 2018). In addition to their ecosystem function, fossil shells of marine calcifiers from sediment cores have long been used to unravel past changes in the marine environment, based upon the assemblage composition, shell morphology and their geochemistry (Spindler and Dieckmann, 1986). The oxygen isotopic composition of WAP foraminiferal calcite shells (termed tests) can be used in the reconstruction of past changes in continental ice volume and water temperature, as well as for age estimation of sediments by stratigraphic correlation (Peck et al, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
