Award: OCE-1924539

This project developed new tools to measure key chemical nutrients and trace metals in seawater more efficiently, more flexibly, and with far less hands-on effort than existing approaches. These measurements are essential for understanding ocean productivity and the health of ocean ecosystems. However, many important nutrients and trace metals are still difficult to measure frequently or autonomously. This limits our ability to observe short-term events such as upwelling, storms, or dust deposition and makes it harder to distinguish natural variability from human impacts. 

The core outcome of this award was the advancement of programmable Flow Injection (pFI) as a versatile analytical platform in chemical oceanography for both shipboard and autonomous chemical measurements. pFI uses a computer controlled fluidic system that can run multiple chemical analyses on the same instrument, while requiring relatively little maintenance and small amounts of reagents. Over the lifetime of the award, we demonstrated this capability for phosphate, silicate, and dissolved aluminium. These parameters are central to ocean productivity (phosphate and silicate) and to probe how trace metals cycle through the oceans (aluminium). 

The project delivered robust chemical methods for phosphate and silicate that can operate autonomously for more than a month without reagent replacement. These methods maintain accuracy and sensitivity while eliminating problematic salt effects, allowing calibration with ultrapure water rather than seawater. This simplification is valuable for long-term deployments and reduces operational complexity. Shipboard testing during international intercomparison exercises showed that the analytical performance of pFI approaches established nutrient auto-analyzers, while offering the added benefit of unattended operation.

A second major outcome was the development of pFIONA (programmable Flow Injection Ocean Nutrient Analyzer), a compact, weatherproof, fully autonomous analyzer built around the pFI concept. pFIONA integrates pumps, valves, optics, and control electronics into a single system controlled by open-source software. The instrument was successfully deployed at a coastal observatory for month-long campaigns, producing hourly measurements of phosphate and silicate and capturing variability associated with tides and upwelling. These deployments demonstrated that high-quality wet-chemical measurements can be made autonomously in real-world environments with the newly developed pFI technology. 

The project also advanced shipboard trace-metal analysis by adapting the classic lumogallion fluorescence method for dissolved aluminium to pFI. This new approach achieves nanomolar sensitivity without the need for complex preconcentration steps or specialized seawater calibration standards. As a result, it lowers technical barriers for trace-metal measurements during oceanographic cruises and provides a simpler alternative to traditional methods.

Beyond its scientific contributions, the project supported training across undergraduate and graduate levels, including interdisciplinary collaborations between chemical oceanography and engineering students. Participants gained experience in analytical chemistry, instrument design, data analysis, and autonomous sensing. Several students completed or are completing graduate master theses based on this work, and others have moved on to careers in marine science and sensor development.

Finally, the project contributes to the broader research community by establishing an open-source platform for chemical sensing. The same hardware and software framework can be adapted to multiple chemical measurements, reducing the need for separate instruments for each analyte. This approach has the potential to improve data consistency, reduce costs, and expand access to high-quality chemical measurements in both oceanographic and freshwater settings.

Together, these outcomes demonstrate that programmable Flow Injection can transform how chemical measurements are made in the environment by making them more flexible, more accessible, and better suited to the growing need for high-frequency observations in a changing world.

Last Modified: 12/12/2025
Modified by: Maxime Grand