Third xFOCE workshop: present status and future developments of in situ ocean acidification experiments

One of the major challenges facing ocean acidification research is the need to expand from single species to communities and ecosystems (Riebesell and Gattuso 2015). Free Ocean CO2 Enrichment (FOCE) experiments were developed to address the need for long term, in situ CO2 manipulation in benthic ecosystems (Gattuso et al. 2014), and to enable community level investigations of the effects of ocean acidification. Theoretically these experiments allow for the precise control of pH in benthic chambers, while maintaining open flow-through conditions including natural background variation in other parameters. xFOCE is the open source technology developed by the Monterey Bay Aquarium Research Institute (MBARI) to enable cost effective and adaptable system design.

With support from the Australian Antarctic Division (AAD) and the 4th International Symposium on the Ocean in a High-CO2 World, a group of 18 past, present and future FOCE users met in Kingston, Hobart (Australia) on 29th April 2016.

Problems with the shallow water FOCE (swFOCE) in Monterey Bay were described by engineer K. Headley (MBARI), including electrical ground faults and software interfacing. Despite these issues MBARI is at the forefront of FOCE design and has contributed to all other FOCE systems.

Valuable lessons in chamber design, power supply and habitat choice were reviewed by F. Gazeau (Laboratoire d’Océanographie de Villefranche, France) from the Mediterranean Sea FOCE (eFOCE) conducted in seagrass beds.

J. Stark (AAD) gave a comprehensive overview of the recent successful Antarctic FOCE (antFOCE) experiment (Fig. 1) and was followed by further antFOCE insights including: deployment under ice in Antarctica (G. Johnstone AAD); engineering of pump systems and enriched seawater (S. Whiteside, AAD); surface based sensors and control of pH via feedback loops (M. Milnes, AAD); carbonate chemistry demonstrating the antFOCE system’s effectiveness in obtaining a 0.4 pH offset (N. Roden, University of Tasmania, UTAS); and preliminary results from work on bioturbation (A. Queiros, Plymouth Marine Laboratories). A very successful addition to FOCE systems was described by J. Black (UTAS), which consisted of smaller chambers designed for short term (48–96h) in situ incubation experiments using water from the antFOCE system.

The antFOCE experiment was deployed in 14m of water under sea ice at Casey Station, in East Antarctica. Mixing ducts 40m long were required to allow pH to equilibrate following the addition of CO2 enriched seawater into the flow-through system.

Although FOCE experiments present many challenges, group consensus was that FOCE systems are now proven to be viable and worthwhile. There are a range of solutions and options to overcome site specific difficulties and adapt FOCE systems to particular scientific needs. Using the combined experience of past efforts we now can make estimates of resources (including personnel) and skills required for successful FOCE experiments. A paper on this topic is being prepared as a result of the workshop. The next challenge for FOCE systems will be to incorporate additional drivers beyond a pH offset, such as temperature or oxygen.

The xFOCE website contains additional information including a list of meeting participants and can be found at

Stark J. S. & Gattuso J.-P., 2016. Third xFOCE workshop: present status and future developments of in situ ocean acidification experiments. Limnology and Oceanography Bulletin. Meeting Highlights. doi: 10.1002/lob.10126. Article.

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