The second WG group meeting was held in Hangzhou, China on 10-11 October 2011. It was hosted by the 2nd Institute of Oceanography. Xiqiu Han, also a member of the WG, has been a greatly appreciated local organiser. The visit included additional exchanges with colleagues and seminars for students for several meeting attendees. The group of attendees involved L. Bharathi (India), T. Gamo (Japan), C. German (US), G. W. Luther (US), X. Han (China), N. Le Bris (France), L. Legendre (France), S. Sander (NZ) and S. Sievert (US).
The first objective of the meeting was to initiate discussion on the two review papers that aim at synthesizing knowledge on : 1) seafloor and subseafloor carbon fixation processes and transfer in the ecosystem, and 2) subseafloor to upper ocean impact on ocean carbon budgets. The second objective was to discuss the synthesis of this information into a conceptual model, allowing us to address the role of ridge hydrothermal systems on the ocean C biogeochemistry on a more quantitative basis. Discussion of the modelling approach was led by L. Legendre on the second day. The two subgroups set the frame for a conceptual basis to these approaches.
The first subgroup addressed the productivity of vent ecosystems, from the perspective of estimating the amount of carbon that is fixed chemosynthetically and can be transferred to consumers or to the water column. The second subgroup considered the potential role that hydrothermal systems may play in regulating global scale carbon budgets and related biogeochemical cycles (notably for the micro-nutrient Fe) in the deep ocean. The building of the two conceptual models has already generated interesting discussions on the priorities and necessary degree of simplification of the first models.
Following the Hangzhou meeting, the two sub-groups have been focusing upon formalizing the model approach, guided by L. Legendre. A preliminary version of the water column model was completed by early 2012 and a revised version of the modelling is now being undertaken. A similar approach has been drafted for the seafloor ecosystem model and is being refined. As done for the water column model, the need is on constraining the unknowns for such complex systems that involve a variety of chemoautotrophic pathways and related abiotic conditions/ energy sources. Further plans will be to circulate draft paper versions to the whole WG, to allow integration of contributions from WG members not attending the workshop.
Early 2013 is being considered for the organisation of this event at a European venue.