A new CALMAR benthic chamber operating by submersible: First application in the cold-seep environment of Napoli mud volcano (Mediterranean Sea)

International audienceA new submersible-operated benthic chamber has been developed to measure benthic organism metabolism and chemical exchange rates at the sediment-water interface up to 6000 m depth. This equipment can be used everywhere on soft sediment, but particularly to deploy it on small area reached only by submersible-like cold seep. The chamber, 41 cm diameter cylinder, includes six 100 mL-sampling cells to isolate aliquots, which are sampled at predetermined intervals and an oxygen-optode probe. This chamber named CALMAR (Chambre Autonome Légère MAnipulable par ROV) was used for the first time during the Medeco cruise (2007) in Eastern Mediterranean Sea. It allowed measurement of fluxes of oxygen, dissolved inorganic carbon, and methane on the Napoli mud volcano site. Two benthic chambers were deployed with the ROV Victor, respectively, on small, active, cold seep colonized by Siboglinidae worms and mussels (Station A), and at about 3 m from the first where no visible animals were observed (Station B). The oxygen flux was 35 mmol O2 m-2 d-1 in sediment colonized by large organisms (Station A) and 13.5 mmol O2 m-2 d-1 on the inactive area (CALMAR B). In terms of inorganic carbon, the fluxes were 34 and 10.5 mmol m-2 d-1, respectively, at A and B, and the calculated respiratory coefficient was 0.97 at A and 0.78 at B. The methane flux was only observed on the Siboglinidae colony (3 mmol m-2 d-1) and not on Station B