A flow-through rolling tank allows to conduct experiments on particulate organic matter at near in-situ conditions.

Downward fluxes of particulate organic matter (POM) are the major sink of atmospheric CO2 into aquatic sediments, remaining there for thousands of years. Budget calculations of the biological carbon pump are greatly based on the ratio between carbon export (sedimentation) and remineralization (release to the atmosphere). Current methodologies determine microbial dynamics on POM using closed vessels, thus, strongly biased towards heterotrophy due to rapidly changing water chemistry (Bottle Effect). We developed a flow-through rolling tank for long term studies that continuously maintains POM at near in-situ conditions. There, bacterial communities follow those in-situ, contrary to rapidly changing ones in closed rolling tanks. The active particle-associated community in the flow-through system is stable over several days contrary to several hours previously reported. Decrease in particles photosynthetic rates is much slower in our system than in traditional ones. These results call for reevaluating experimentally-derived carbon fluxes, using our new experimental tool.