Data for Sun et al. (2024) 'The Role of Acantharia in Southern Ocean Strontium Cycling and Carbon Export: Insights from Dissolved Strontium Concentrations and Seasonal Flux Patterns'

Description

This record presents the strontium (Sr) data used in the paper 'The Role of Acantharia in Southern Ocean Strontium Cycling and Carbon Export: Insights from Dissolved Strontium Concentrations and Seasonal Flux Patterns', Sun et al. (2024). All methods for the dataset are thoroughly documented and cross-referenced in the paper. Introduction: The dataset examines how Acantharia, marine protists with celestite (SrSO4) skeletons, influence strontium (Sr) and carbon cycling in the Southern Ocean. Acantharia utilize surface Sr to build skeletons and release it upon death, significantly impacting Sr distribution. Their cysts, also celestite-based, act as effective ballast for particulate organic carbon (POC). Analysis of dissolved and particulate Sr concentrations indicates Acantharia's dominant role in Sr cycles, with seasonal flux variations, particularly intense in January/February, likely linked to increased productivity and ocean temperatures during that period. Sampling Sites: Dissolved and particulate Sr samples were collected in the Australian sector of the Southern Ocean during R/V Investigator voyages IN2018_V01 and IN2020_V08. The IN2018_V01 voyage was conducted between 10 January and 22 February 2018, along the SR3 transect (44°S – 66°S, 140°E – 146°E). The IN2020_V08 voyage was carried out between 4 December 2020, and 15 January 2021, with sampling conducted at three primary sites. Samples were collected at three primary sites: the Southern Ocean Time Series (SOTS) site (47°S, 141°E), and two southern sites (SS1 and SS2) located within a polar bloom at approximately 55°S, 138°E, and 58°S, 141°E, respectively. Seasonal surface and deep ocean mooring samples are archived samples collected at the SOTS site from long-term SOTS moorings and measured for Sr from selected years. Sampling Methodology: Dissolved Sr samples were collected using CTD rosettes at various depths. Particulate Sr samples were obtained using McLane pumps, focusing on subsurface waters to estimate the standing stock of Acantharia. Surface mooring samples were collected using a Remote Access Sampler (RAS-599, McLane Labs) and filtered through a 1mm plastic mesh on the sample inlet. The deep ocean mooring samples were collected from 1000 m sediment traps. The cups were buffered with SrCl2 prior to deployment to prevent the dissolution of Acantharia. After recovery, the cups were separated into >1mm and <1mm fractions. The >1mm fraction was archived in buffered seawater, while the <1mm fraction was dried and homogenized into powders. Data Analysis: All the samples were digested and/or diluted in 2% HNO3 and measured on the ICP-OES for Sr concentrations. The results were normalized to a salinity of 35. Uncertainty in Sr measurements was assessed based on the average one standard deviation of triplicate measurements across the dataset.

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