Designing a Molecular Radar to Characterize the Ocean Surface Microlayer

The ocean surface microlayer (OSM) is a small and harsh ecosystem at the millimetre-scale interface between the atmosphere and ocean. Its inhabitants include an accumulation of bacteria that are attracted to the OSM by nutrients deposited from above by aerosols. Despite adverse conditions such as high UV exposure, this region is known to host dense populations of bacteria. The role played by these bacteria in the global climate and ecosystem is not yet well understood, but they and the signals driving their accumulation may influence biogenic mixing (driving large-scale transport within the ocean) and ocean carbon capture.

In this project we consider the OSM through the lens of molecular communication, which offers an interdisciplinary outside-the-box approach to study molecule transport processes. By applying communications systems concepts to biophysical models, we can offer insights into how molecular signals propagate and what information they carry, implicitly and explicitly. For example, a propagating signal implicitly carries information about the environment that it passed through before it was observed.

Here, we plan to design and test a new ocean measurement system that we refer to as "molecular radar". In this system, molecules are emitted at the ocean surface as a control signal, the molecules propagate through the OSM, and they are detected and measured below the OSM. By analyzing these signals using 'inversion', we can estimate the properties of the OSM (e.g., the layer size and associated diffusion coefficients). We will achieve and validate this proof-of-concept with the combined expertise of the research team, using a combination of analytical modeling, particle simulation, laboratory experimentation, and physics-informed machine-learning approaches.