Sedimentation dynamics and microbial degradation of marine aggregates: hydrodynamic fundamentals of particulate carbon transport in the ocean

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Marine aggregates build the backbone of biological carbon pump in the ocean by exporting the particulate organic carbon into the deeper water layers via sedimentation.We target at constructing a combined hydrodynamic-microbiological project for characterization of effective vertical transport by marine aggregates with special emphasis on microbial turnover rates within the aggregates. By combining the laboratory experiments with numerical simulations, we first parametrize the sinking velocity of the aggregates as a function of size, porosity, composition and density stratification of the ambient fluid. Next, the mass transfer between the interstitial fluid and the ambient water as well as the microbial turnover rates within the aggregates will be determined as a function of sinking velocity. Based on this, a mathematical model will be developed which mimics reliably the sinking velocity and mass transfer. Such a model will enable us for the first time to provide a realistic estimation of the efficiency of the biological carbon pump. Furthermore, the model delivers valuable inputs and approaches to integrate marine processes into available global climate and oceanic carbon circulation models.