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

海洋聚集体通过沉降将颗粒有机碳输出到更深的水层，构成了海洋生物碳泵的支柱。我们的目标是建立一个流体动力学-微生物学联合项目，以表征海洋聚集体的有效垂直运输，特别强调聚集体内的微生物周转率。通过室内实验与数值模拟相结合，我们首先将聚集体的下沉速度参数化为周围流体的大小、孔隙度、组成和密度分层的函数。接下来，将确定间隙流体与周围水之间的传质以及聚集体内的微生物周转率作为下沉速度的函数。在此基础上，将建立一个可靠地模拟下沉速度和传质的数学模型。这样的模型将使我们第一次能够对生物碳泵的效率提供一个现实的估计。此外，该模式还提供了宝贵的输入和方法，将海洋过程整合到现有的全球气候和海洋碳循环模式中。

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.