The Role of Acantharia in Southern Ocean Strontium Cycling and Carbon
Export: Insights from Dissolved Strontium Concentrations and Seasonal
Flux Patterns
Abstract
Dissolved strontium (Sr) concentrations in the Southern Ocean water
samples and Sr export fluxes from sediment trap moorings at 1000 m were
used to assess particulate organic carbon (POC) export associated with
Acantharia for 2010, 2018 and 2020. The dissolved Sr data revealed a
prominent vertical gradient with lower surface Sr concentrations
depleted up to 1.4% relative to deep waters. A strong latitudinal
surface gradient was observed, ranging from 87.3 near the northern end
to 88.5 near the southern end of a transect through the Australian
sector of the Southern Ocean. These findings highlight the significant
role that Acantharia, which precipitate celestite (SrSO4), play in
marine Sr cycling. Seasonal variability in Sr export fluxes can be
large, particularly during intense events in summer, and reaches a
maximum of 2.8 , contributing up to 7% of the POC export flux. The
coincidence of Sr flux with the second peak of POC export flux implies a
potential association of Acantharia biomass with summertime
productivity.