The Southern Ocean is anaemic, with phytoplankton growth being slowed by the lack of the micronutrient iron. Phytoplankton are the base of the food chain, but they also take up carbon dioxide through photosynthesis. This anaemia therefore limits the potential of the Southern Ocean to absorb carbon dioxide, and as a result, the ACECRC in collaboration with CSIRO is interested in studying its spatial and temporal distribution. Measuring iron in the ocean is hard due to the ease of contamination from research ships and sampling equipment. However, due to the expertise at the ACECRC and CSIRO, we have developed a system to observe the changes in iron concentration over a full seasonal cycle.
A trace metal clean seawater sampler has been developed for 1 year deployments on oceanographic moorings. Twelve samples per unit can be programmed to collect 65 ml of seawater at any time interval. The sample path is made entirely out of Teflon and 1m intake tubes allow uncontaminated sampling in upstream water. Samples are drawn into the sampling containers via micro-peristaltic pumps.
The unit itself is non-contaminating, being made of polycarbonate, Teflon and titanium. The system is pressure compensated and has successfully been tested to 100 m. Blank testing of the system deployed in the Southern Ocean in January 2018 revealed no significant difference between an industry standard, trace metal rosette in the 100 pM range, proving its capability at collecting uncontaminated samples in the oligotrophic open ocean. A spin off project saw the “TM sampler” partially redesigned for rapid turnaround deployments on the Australian Maritime College, 5 million dollar, autonomous underwater vehicle, ‘nupiri muka’ with funding made available through the Antarctic Gateway Project, the Antarctic Climate and Ecosystems CRC and CSIRO. During testing, the TM sampler was mounted within the AUV, with its intake tubes extending outside of the turbulent flow around the AUV’s hull (see image) to avoid