ACE water sampler: sample processing, analysis and interpretation of Southern Ocean Time Series trace element data

Supervisory Team:

Primary supervisor: Dr Pier van der Merwe

Co-supervisor: Dr Elizabeth Shadwick (CSIRO), Professor Andrew Bowie

Brief project description:

The fundamental role of the micronutrient Fe in controlling phytoplankton growth in large parts of Earth’s oceans and a lack of information on seasonal transitions in remote regions motivated us to create an autonomous water sampler capable of collecting uncontaminated open-ocean sea water samples with monthly resolution over a full annual cycle.

Phytoplankton are the base of the food chain, and take up carbon dioxide through photosynthesis and assessing Fe availability is thus essential to understanding both ocean productivity and our climate. This need is particularly important in the Southern Ocean where Fe limitation is widespread, and access is difficult, especially in winter.

To address this need, we have developed an autonomous system capable of observing iron concentrations over a full seasonal cycle, at the sub-nanomolar concentrations that are important in the open ocean. The ACE (automated clean environmental) sampler has been developed initially for 1-year deployments on oceanographic moorings. Twelve samples per unit can be programmed to collect 65 ml of seawater through a non-contaminating, primarily Teflon sample path.

During this project, the student will work alongside the team who created the ACE sampler to process seawater samples for trace metal analysis. Seawater samples will be processed through a SeaFast Preconcentration system and then analysed using an Inductively Coupled Plasma, Mass Spectrometer (ICPMS).  The resultant data will then be checked for oceanographic consistency and interpreted within the framework of our current understanding of Fe cycling in the Southern Ocean.

Given the deployment location at the Southern Ocean Time Series Observatory, a wealth of supporting data is available to build a coherent picture of the oceanographic processes occurring at the site. Supporting data (macronutrients, chlorophyll fluorescence, temperature, salinity, dissolved oxygen, alkalinity, pCO2, phytoplankton community data and sediment trap particle flux) will be accessed through the Australian Ocean Data Network portal and combined into a report or publication.

Skills students will develop during this research project:

  • Stringent trace element sample handling and laboratory procedures
  • Analytical chemistry: Seafast Pico preconcentration and ICPMS analysis
  • Data mining using online portals
  • Data interpretation
  • Report writing and/or publication.
Authorised by the Executive Director, Institute for Marine and Antarctic Studies
March 12, 2021