Reply to comment: Controls on turnover of marine dissolved organic matter-testing the null hypothesis of purely concentration-driven uptake

Our recent bioassay experiments indicate that molecular properties are a primary control on the microbial utilization of dissolved organic matter in the ocean. This finding is questioned by Lennartz and Dittmar who modeled our experiments and concluded that our observations could be largely explained by concentration-driven uptake independent from molecular properties. We suggest the authors' models are deficient for establishing the relative roles of molecular properties and concentration-driven uptake. Our conclusion is consistent with earlier and recent experimental results and biogeochemical observations, supporting a unified theory with molecular properties as a more prominent control than concentration-driven uptake on marine organic carbon accumulation.

Automated summary

Recent bioassay experiments suggest that the microbial utilization of dissolved organic matter in the ocean is primarily regulated by molecular properties. However, a modeling study conducted by Lennartz and Dittmar challenges this finding, proposing that concentration-driven uptake may largely explain the observed results. We argue that their models are insufficient to establish the relative roles of molecular properties and concentration-driven uptake.